ANIMA WG                                                  T. Eckert, Ed.
Internet-Draft                                                    Huawei
Intended status: Standards Track                       M. Behringer, Ed.
Expires: June 20, December 8, 2018
                                                            S. Bjarnason
                                                          Arbor Networks
                                                       December 17, 2017
                                                            June 6, 2018

                    An Autonomic Control Plane (ACP)
              draft-ietf-anima-autonomic-control-plane-13
              draft-ietf-anima-autonomic-control-plane-14

Abstract

   Autonomic functions need a control plane to communicate, which
   depends on some addressing and routing.  This Autonomic Management
   and Control Plane should ideally be self-managing, and as independent
   as possible of configuration.  This document defines such a plane and
   calls it the "Autonomic Control Plane", with the primary use as a
   control plane for autonomic functions.  It also serves as a "virtual
   out of band
   out-of-band channel" for OAM (Operations Operations Administration and
   Management) Management
   (OAM) communications over a network that is secure and reliable even
   when the network is not configured, or not misconfigured.

Status of This Memo

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   This Internet-Draft will expire on June 20, December 8, 2018.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
     1.1.  Applicability and Scope . . . . . . . . . . . . . . . . .   7
   2.  Acronyms and Terminology  . . . . . . . . . . . . . . . . . .   6   8
   3.  Use Cases for an Autonomic Control Plane  . . . . . . . . . .  11  13
     3.1.  An Infrastructure for Autonomic Functions . . . . . . . .  11  13
     3.2.  Secure Bootstrap over a not configured Network  . . . . .  11  13
     3.3.  Data-Plane Independent Permanent Reachability . . . . . .  11  14
   4.  Requirements  . . . . . . . . . . . . . . . . . . . . . . . .  12  15
   5.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .  13  16
   6.  Self-Creation of an Autonomic Control Plane (ACP) (Normative)  14  17
     6.1.  ACP Domain, Certificate and Network . . . . . . . . . . .  15  17
       6.1.1.  Certificate Domain Information Field  . . . . . . . .  16  19
       6.1.2.  ACP domain membership check . . . . . . . . . . . . .  18  21
       6.1.3.  Certificate Maintenance . . . . . . . . . . . . . . .  19  22
     6.2.  ACP Adjacency Table . . . . . . . . . . . . . . . . . . .  21  27
     6.3.  Neighbor Discovery with DULL GRASP  . . . . . . . . . . .  21  27
     6.4.  Candidate ACP Neighbor Selection  . . . . . . . . . . . .  24  30
     6.5.  Channel Selection . . . . . . . . . . . . . . . . . . . .  25  31
     6.6.  Candidate ACP Neighbor verification . . . . . . . . . . .  26  33
     6.7.  Security Association protocols  . . . . . . . . . . . . .  27  33
       6.7.1.  ACP via IKEv2 . . . . . . . . . . . . . . . . . . . .  27  33
       6.7.2.  ACP via dTLS DTLS  . . . . . . . . . . . . . . . . . . . .  28  34
       6.7.3.  ACP Secure Channel Requirements . . . . . . . . . . .  28  35
     6.8.  GRASP in the ACP  . . . . . . . . . . . . . . . . . . . .  29  35
       6.8.1.  GRASP as a core service of the ACP  . . . . . . . . .  29  35
       6.8.2.  ACP as the Security and Transport substrate for GRASP  30  36
     6.9.  Context Separation  . . . . . . . . . . . . . . . . . . .  33  39
     6.10. Addressing inside the ACP . . . . . . . . . . . . . . . .  34  39
       6.10.1.  Fundamental Concepts of Autonomic Addressing . . . .  34  40
       6.10.2.  The ACP Addressing Base Scheme . . . . . . . . . . .  35  41
       6.10.3.  ACP Zone Addressing Sub-Scheme . . . . . . . . . . .  36  42
       6.10.4.  ACP Manual Addressing Sub-Scheme . . . . . . . . . .  39  44
       6.10.5.  ACP Vlong Addressing Sub-Scheme  . . . . . . . . . .  40  46
       6.10.6.  Other ACP Addressing Sub-Schemes . . . . . . . . . .  41  47
       6.10.7.  ACP Registrars . . . . . . . . . . . . . . . . . . .  47
     6.11. Routing in the ACP  . . . . . . . . . . . . . . . . . . .  41  50
       6.11.1.  RPL Profile  . . . . . . . . . . . . . . . . . . . .  42  51
     6.12. General ACP Considerations  . . . . . . . . . . . . . . .  45  54
       6.12.1.  Performance  . . . . . . . . . . . . . . . . . . . .  45  55
       6.12.2.  Addressing of Secure Channels in the data-plane Data-Plane  . .  46  55
       6.12.3.  MTU  . . . . . . . . . . . . . . . . . . . . . . . .  46  55
       6.12.4.  Multiple links between nodes . . . . . . . . . . . .  47  56
       6.12.5.  ACP interfaces . . . . . . . . . . . . . . . . . . .  47  56
   7.  ACP support on L2 switches/ports (Normative)  . . . . . . . .  50  59
     7.1.  Why . . . . . . . . . . . . . . . . . . . . . . . . . . .  50  59
     7.2.  How (per L2 port DULL GRASP)  . . . . . . . . . . . . . .  51  60
   8.  Support for Non-ACP Components (Normative)  . . . . . . . . .  53  62
     8.1.  ACP Connect . . . . . . . . . . . . . . . . . . . . . . .  53  62
       8.1.1.  Non-ACP Controller / NMS system . . . . . . . . . . .  53  62
       8.1.2.  Software Components . . . . . . . . . . . . . . . . .  55  64
       8.1.3.  Auto Configuration  . . . . . . . . . . . . . . . . .  56  65
       8.1.4.  Combined ACP/Data-Plane Interface (VRF Select)  . . .  57  66
       8.1.5.  Use of GRASP  . . . . . . . . . . . . . . . . . . . .  58  67
     8.2.  ACP through Non-ACP L3 Clouds (Remote ACP neighbors)  . .  59  68
       8.2.1.  Configured Remote ACP neighbor  . . . . . . . . . . .  59  68
       8.2.2.  Tunneled Remote ACP Neighbor  . . . . . . . . . . . .  61  70
       8.2.3.  Summary . . . . . . . . . . . . . . . . . . . . . . .  61  70
   9.  Benefits (Informative)  . . . . . . . . . . . . . . . . . . .  61  70
     9.1.  Self-Healing Properties . . . . . . . . . . . . . . . . .  61  70
     9.2.  Self-Protection Properties  . . . . . . . . . . . . . . .  63  72
       9.2.1.  From the outside  . . . . . . . . . . . . . . . . . .  63  72
       9.2.2.  From the inside . . . . . . . . . . . . . . . . . . .  63  73
     9.3.  The Administrator View  . . . . . . . . . . . . . . . . .  64  73
   10. Further Considerations (Informative)  . . . . . . . . . . . .  65  74
     10.1.  BRSKI Bootstrap (ANI)  . . . . . . . . . . . . . . . . .  65  74
     10.2.  ACP (and BRSKI) Diagnostics  . . . . . . . . . . . . . .  66  75
     10.3.  ACP Registrar Considerations . . . . . . . . . . . . . .  80
       10.3.1.  Registrar interactions . . . . . . . . . . . . . . .  80
       10.3.2.  Registrar Parameter  . . . . . . . . . . . . . . . .  81
       10.3.3.  Certificate renewal and limitations  . . . . . . . .  82
       10.3.4.  ACP Registrars with sub-CA . . . . . . . . . . . . .  83
       10.3.5.  Centralized Policy Control . . . . . . . . . . . . .  83
     10.4.  Address Space Considerations . . . . . . . . . . . . . .  84
     10.5.  Enabling and disabling ACP/ANI . . . . . . . . . . . . .  71
       10.3.1.  85
       10.5.1.  Filtering for non-ACP/ANI packets  . . . . . . . . .  71
       10.3.2.  85
       10.5.2.  Admin Down State . . . . . . . . . . . . . . . . . .  72
       10.3.3.  86
       10.5.3.  Interface level ACP/ANI enable . . . . . . . . . . .  74
       10.3.4.  88
       10.5.4.  Which interfaces to auto-enable ? auto-enable? . . . . . . . . .  75
       10.3.5. .  89
       10.5.5.  Node Level ACP/ANI enable  . . . . . . . . . . . . .  76
       10.3.6.  90
       10.5.6.  Undoing ANI/ACP enable . . . . . . . . . . . . . . .  78
       10.3.7.  92
       10.5.7.  Summary  . . . . . . . . . . . . . . . . . . . . . .  78
     10.4.  92
     10.6.  ACP Neighbor discovery protocol selection  . . . . . . .  78
       10.4.1.  92
       10.6.1.  LLDP . . . . . . . . . . . . . . . . . . . . . . . .  79
       10.4.2.  93
       10.6.2.  mDNS and L2 support  . . . . . . . . . . . . . . . .  79
       10.4.3.  93
       10.6.3.  Why DULL GRASP . . . . . . . . . . . . . . . . . . .  79
     10.5.  93
     10.7.  Choice of routing protocol (RPL) . . . . . . . . . . . .  80
     10.6.  94
     10.8.  ACP Information Distribution and multicast . . . . . . .  95
     10.9.  Extending ACP channel negotiation (via GRASP)  . . . . .  81
     10.7.  96
     10.10. CAs, domains and routing subdomains  . . . . . . . . . .  83
     10.8.  98
     10.11. Adopting ACP concepts for other environments . . . . . .  84  99
   11. Security Considerations . . . . . . . . . . . . . . . . . . .  86 101
   12. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  87 103
   13. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  88 103
   14. Change log [RFC Editor: Please remove]  . . . . . . . . . . .  88 104
     14.1.  Initial version  . . . . . . . . . . . . . . . . . . . .  88 104
     14.2.  draft-behringer-anima-autonomic-control-plane-00 . . . .  88 104
     14.3.  draft-behringer-anima-autonomic-control-plane-01 . . . .  88 104
     14.4.  draft-behringer-anima-autonomic-control-plane-02 . . . .  89 104
     14.5.  draft-behringer-anima-autonomic-control-plane-03 . . . .  89 104
     14.6.  draft-ietf-anima-autonomic-control-plane-00  . . . . . .  89 105
     14.7.  draft-ietf-anima-autonomic-control-plane-01  . . . . . .  89 105
     14.8.  draft-ietf-anima-autonomic-control-plane-02  . . . . . .  90 106
     14.9.  draft-ietf-anima-autonomic-control-plane-03  . . . . . .  90 106
     14.10. draft-ietf-anima-autonomic-control-plane-04  . . . . . .  91 106
     14.11. draft-ietf-anima-autonomic-control-plane-05  . . . . . .  91 107
     14.12. draft-ietf-anima-autonomic-control-plane-06  . . . . . .  92 107
     14.13. draft-ietf-anima-autonomic-control-plane-07  . . . . . .  92 108
     14.14. draft-ietf-anima-autonomic-control-plane-08  . . . . . .  94 109
     14.15. draft-ietf-anima-autonomic-control-plane-09  . . . . . .  95 111
     14.16. draft-ietf-anima-autonomic-control-plane-10  . . . . . .  97 113
     14.17. draft-ietf-anima-autonomic-control-plane-11  . . . . . .  99 115
     14.18. draft-ietf-anima-autonomic-control-plane-12  . . . . . .  99 115
     14.19. draft-ietf-anima-autonomic-control-plane-13  . . . . . . 101 116
     14.20. draft-ietf-anima-autonomic-control-plane-14  . . . . . . 118
     14.21. wish-list  . . . . . . . . . . . . . . . . . . . . . . . 122
   15. References  . . . . . . . . . . . . . . . . . . . . . . . . . 103 122
     15.1.  Normative References . . . . . . . . . . . . . . . . . . 103 122
     15.2.  Informative References . . . . . . . . . . . . . . . . . 105 125
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . 109 129

1.  Introduction

   Autonomic Networking is a concept of self-management: Autonomic
   functions self-configure, and negotiate parameters and settings
   across the network.  [RFC7575] defines the fundamental ideas and
   design goals of Autonomic Networking.  A gap analysis of Autonomic
   Networking is given in [RFC7576].  The reference architecture for
   Autonomic Networking in the IETF is currently being defined specified in the document
   [I-D.ietf-anima-reference-model]

   Autonomic functions need an autonomically built communications
   infrastructure or network plane (there is no well-established name
   for this).
   infrastructure.  This infrastructure needs to be secure, resilient
   and re-
   usable re-usable by all autonomic functions.  Section 5 of [RFC7575]
   introduces that infrastructure and calls it the "Autonomic Autonomic Control Plane"
   Plane (ACP).  More descriptively it would be the "Autonomic
   communications infrastructure for Management and Control".  For
   naming consistency with that prior document, this document continues
   to use the name ACP though.

   Today, the management and control plane of networks typically runs in uses
   the global routing table, which is dependent on correct configuration
   and routing.  Misconfigurations or routing problems can therefore
   disrupt management and control channels.  Traditionally, an out of out-of-
   band network has been used to recover avoid or allow recovery from such
   problems, or personnel is are sent on site to access devices through
   console ports (craft ports).  However, both options are expensive.

   In increasingly automated networks either centralized management
   systems or distributed autonomic service agents in the network
   require a control plane which is independent of the configuration of
   the network they manage, to avoid impacting their own operations
   through the configuration actions they take.

   This document describes a modular design for a self-forming, self-
   managing and self-protecting "Autonomic Autonomic Control Plane" (ACP) Plane (ACP), which is
   a virtual in-band network designed to be as independent as possible
   of configuration, addressing and routing problems.  The details how
   this achieved are defined in Section 6.  The ACP is designed to
   remains operational even in the presence of configuration errors,
   addressing or routing issues, or where policy could inadvertently
   affect connectivity of both data packets or control packets.

   This document uses the term "data-plane" "Data-Plane" to refer to anything in the
   network nodes that is not the ACP, and therefore considered to be
   dependent on (mis-)configuration.  This data-plen Data-Plane includes both the
   traditional forwarding-plane, as well as any pre-existing control-
   plane, such as routing protocols that establish routing tables for
   the forwarding plane.

   The Autonomic Control Plane serves several purposes at the same time:

   o

   1.  Autonomic functions communicate over the ACP.  The ACP therefore
       supports directly Autonomic Networking functions, as described in
       [I-D.ietf-anima-reference-model].  For example, GRASP
      [I-D.ietf-anima-grasp] Generic Autonomic
       Signaling Protocol (GRASP - [I-D.ietf-anima-grasp]) runs securely
       inside the ACP and depends on the ACP as its "security and
       transport substrate".

   o  An operator can use it to log into remote devices, even if the
      network is misconfigured or not configured.

   o

   2.  A controller or network management system can use it to securely
       bootstrap network devices in remote locations, even if the
       network in between is not yet configured; no data-plane Data-Plane dependent
       bootstrap configuration is required.  An example of such a secure
       bootstrap process is described in
       [I-D.ietf-anima-bootstrapping-keyinfra]

   3.  An operator can use it to log into remote devices, even if the
       network is misconfigured or not configured.

   This document describes these purposes as use cases for the ACP in
   Section 3, it defines the requirements in Section 4.  Section 5 gives
   an overview how the ACP is constructed, and in Section 6 the process
   is defined in detail.  Section 7 defines how to support ACP on L2
   switches.  Section 8 explains how non-ACP nodes and networks can be
   integrated.

   The following sections are non-normative: Section 9 reviews benefits
   of the ACP (after all the details have been defined), Section 10
   provides additional explanations and describes additional details or
   future work possibilities that where considered not to be appropriate
   for standardization in this document but nevertheless assumed to be
   helpful for candidate adopters of the ACP.

   The ACP provides secure IPv6 connectivity, therefore it can not only
   be used as defined the secure connectivity for self-management as required
   for the ACP in this document [RFC7575], but it can also be used as the secure
   connectivity for traditional (centralized) management.  The ACP can
   be implemented and operated without dependency against any other components of autonomic networks
   networks, except for the GRASP protocol on which it depends. leverages.

   The document
   "Autonomic Network "Using Autonomic Control Plane for Stable Connectivity"
   [I-D.ietf-anima-stable-connectivity] describes how Connectivity
   of Network OAM" [RFC8368] describes how the ACP alone can be used to
   provide secure and stable connectivity for autonomic and non-
   autonomic OAM applications ("Operations Operations Administration and
   Management").  It Management (OAM)
   applications.  That document also explains on how existing management
   solutions can leverage the ACP in parallel with traditional
   management models, when to use the ACP and, and how to integrate with
   potentially IPv4 based management, etc. only OAM backends.

   Combining ACP with BRSKI ("Bootstrapping Bootstrapping Remote Secure Key
   Infrastructures", Infrastructures
   (BRSKI), see [I-D.ietf-anima-bootstrapping-keyinfra]) results in the
   "Autonomic Network Infrastructure" as defined in
   [I-D.ietf-anima-reference-model].
   [I-D.ietf-anima-reference-model], which provides autonomic
   connectivity (from ACP) with full fully secure zero touch zero-touch (automated)
   bootstrap (from
   BRSKI). from BRSKI.  The ANI itself does not constitute an
   Autonomic Network, but it enables allows the building of more or less
   autonomic networks on top of it - using either centralized, SDN ("Software Software
   Defined Networking", see
   [RFC7426]) Networking (SDN) (see [RFC7426]), style automation or
   distributed automation via ASA
   ("Autonomic Autonomic Service Agents") Agents (ASA) / "Autonomic Functions" Autonomic
   Functions (AF) - or a mixture of both.  See
   [I-D.ietf-anima-reference-model] for more information.

1.1.  Applicability and Scope

   Please see the following Terminology section (Section 2) for
   explanations of terms used in this section.

   The design of the ACP as defined in this document is considered to be
   applicable to all types of "professionally managed" networks: Service
   Provider, Local Area Network (LAN), Metro(politan networks), Wide
   Area Network (WAN), Enterprise Information Technology (IT) and
   Operational Technology (OT) networks.  The ACP can operate equally on
   layer 3 equipment and on layer 2 equipment such a bridges (see
   Section 7).  The encryption mechanism used by the ACP is defined to
   be negotiable, therefore it can be extended to environments with
   different encryption protocol preferences.  The minimum
   implementation requirements in this document attempt to achieve
   maximum interoperability by requiring support for few options: IPsec,
   DTLS - depending on type of device.

   The implementation footprint of the ACP consists of Public Key
   Infrastructure (PKI) code for the ACP certificate, the GRASP
   protocol, UDP, TCP and TLS (for security and reliability of GRASP),
   the ACP secure channel protocol used (such as IPsec or DTLS), and an
   instance of IPv6 packet forwarding and routing via the RPL routing
   protocol ([RFC6550]) that is separate from routing and forwarding for
   the Data-Plane (user traffic).

   The ACP uses only IPv6 to avoid complexity of dual-stack ACP
   operations (IPv6/IPv4).  Nevertheless, it can without any changes be
   integrated into even otherwise IPv4-only network devices.  The Data-
   Plane itself would not need to change, it could continue to be IPv4
   only.  For such IPv4 only devices, the IPv6 protocol itself would be
   additional implementation footprint only used for the ACP.

   The protocol choices of the ACP are primarily based on wide use and
   support in networks and devices, well understood security properties
   and required scalability.  The ACP design is an attempt to produce
   the lowest risk combination of existing technologies and protocols to
   build a widely applicable operational network management solution:

   RPL was chosen because it requires a smaller routing table footprint
   in large networks compared to other routing protocols with an
   autonomically configured single area.  The deployment experience of
   large scale Internet of Things (IoT) networks serves as the basis for
   wide deployment experience with RPL.  The profile chosen for RPL in
   the ACP does not not leverage any RPL specific forwarding plane
   features (IPv6 extension headers), making its implementation a pure
   control plane software requirement.

   GRASP is the only completely novel protocol used in the ACP, and this
   choice was necessary because there is no existing suitable protocol
   to provide the necessary functions to the ACP, so GRASP was developed
   to fill that gap.

   The ACP design can be applicable to (cpu, memory) constrained devices
   and (bitrate, reliability) constrained networks, but this document
   does not attempt to define the most constrained type of devices or
   networks to which the ACP is applicable.  RPL and DTLS are two
   protocol choices already making ACP more applicable to constrained
   environments.  See Section 10.11 for discussions about how variations
   of the ACP could be defined in the future to better meet different
   expectations from those on which the current design is based.

2.  Acronyms and Terminology

   In the rest of the document we will refer to systems using the ACP as
   "nodes".  Typically such a node is a physical (network equipment)
   device, but it can equally be some virtualized system.  Therefore, we
   do not refer to them as devices unless the context specifically calls
   for a physical system.

   This document introduces or uses the following terms (sorted
   alphabetically).  Terms introduced are explained on first use, so
   this list is for reference only.

   ACP:  "Autonomic Control Plane".  The Autonomic Function as defined
      in this document.  It provides secure zero-touch (automated)
      transitive (network wide) IPv6 connectivity for all nodes in the
      same ACP domain as well as a GRASP instance running across this
      ACP IPv6 connectivity.  The ACP is primarily meant to be used as a
      component of the ANI to enable Autonomic Networks but it can
      equally be used in simple ANI networks (with no other Autonomic
      Functions) or completely by itself.

   ACP address:  An IPv6 address assigned to the ACP node.  It is stored
      in the domain information field of the ACP ->"ACP domain certificate
      (Paragraph 21). certificate"
      ().

   ACP address range/set:  The ACP address may imply a range or set of
      addresses that the node can assign for different purposes.  This
      address range/set is derived by the node from the format of the
      ACP address called the "addressing sub-scheme".

   ACP connect: connect interface:  An interface on an ACP node providing access
      to the ACP for non ACP capable nodes without using an ACP secure
      channel.  See Section 8.1.1.

   ACP domain:  The ACP domain is the set of nodes with ->"ACP domain
      certificates
      certificates" that allow them to authenticate each other as
      members of the ACP domain.  See also Section 6.1.2.

   ACP (ANI/AN) Domain Certificate:  A provisioned [RFC5280] certificate
      (LDevID) carrying the domain information field which is used by
      the ACP to learn its address in the ACP and to derive and
      cryptographically assert its membership in the ACP domain.

   domain information (field):  An rfc822Name information element (e.g.: (e.g.,
      field) in the domain certificate in which the ACP relevant
      information is encoded: the domain name and the ACP address.

   ACP loopback Loopback interface:  The loopback Loopback interface in the ACP VRF that
      has the ACP address assigned to it.

   ACP network:  The ACP network constitutes all the nodes that have
      access to the ACP.  It is the set of active and transitively
      connected nodes of an ACP domain plus all nodes that get access to
      the ACP of that domain via ACP edge nodes.

   ACP (ULA) prefix(es):  The /48 IPv6 address prefixes routed used across the
      ACP.  In the normal/simple case, the ACP has one ULA prefix, see
      Section 6.10.  The ACP routing table may include multiple ULA
      prefixes if the "rsub" option is used to create addresses from
      more than one ULA prefix.  See Section 6.1.1.  The ACP may also
      include non-ULA prefixes if those are configured on ACP connect
      interfaces.  See Section 8.1.1.

   ACP secure channel:  A security association established hop-by-hop
      between adjacent ACP nodes to carry traffic of the ACP VRF
      separated from data-plane Data-Plane traffic in-band over the same links as
      the data-plane. Data-Plane.

   ACP secure channel protocol:  The protocol used to build an ACP
      secure channel, e.g.: IKEv2/IPsec e.g., Internet Key Exchange Protocol version 2
      (IKEv2) with IPsec or dTLS. Datagram Transport Layer Security (DTLS).

   ACP virtual interface:  An interface in the ACP VRF mapped to one or
      more ACP secure channels.  See Section 6.12.5.

   AN "Autonomic Network": A network according to
      [I-D.ietf-anima-reference-model].  Its main components are ANI,
      Autonomic Functions and Intent.

   (AN) Domain Name:  An FQDN (Fully Qualified Domain Name) in the
      domain information field of the Domain Certificate.  See
      Section 6.1.1.

   ANI (nodes/network):  "Autonomic Network Infrastructure".  The ANI is
      the infrastructure to enable Autonomic Networks.  It includes ACP,
      BRSKI and GRASP.  Every Autonomic Network includes the ANI, but
      not every ANI network needs to include autonomic functions beyond
      the ANI (nor intent).  An ANI network without further autonomic
      functions can for example support secure zero touch zero-touch (automated)
      bootstrap and stable connectivity for SDN networks - see
      [I-D.ietf-anima-stable-connectivity].
      [RFC8368].

   ANIMA:  "Autonomic Networking Integrated Model and Approach".  ACP,
      BRSKI and GRASP are products of the IETF ANIMA working group.

   ASA:  "Autonomic Service Agent".  Autonomic software modules running
      on an ANI device.  The components making up the ANI (BRSKI, ACP,
      GRASP) are also described as ASAs.

   Autonomic Function:  A function/service in an Autonomic Network (AN)
      composed of one or more ASA across one or more ANI nodes.

   BRSKI:  "Bootstrapping Remote Secure Key Infrastructures"
      ([I-D.ietf-anima-bootstrapping-keyinfra].  A protocol extending
      EST to enable secure zero touch zero-touch bootstrap in conjunction with ACP.
      ANI nodes use ACP, BRSKI and GRASP.

   data-plane:

   Data-Plane:  The counterpoint to the ACP VRF in an ACP node: all VRFs
      routing and forwarding in the node other than the ACP VRF.  In a
      simple ACP or ANI node, the data-
      plane Data-Plane is typically provisioned
      non-autonomic, for example manually (including across the ACP) or
      via SDN controllers.  In a full fully Autonomic Network node, the data-plane Data-
      Plane is managed autonomically via Autonomic Functions and Intent.
      Note that other (non-ANIMA) RFC use the data-plane Data-Plane to refer to
      what is better called the forwarding plane.  This is not the way
      the term is used in this document!

   ACP (ANI/AN) Domain Certificate:  A provisioned certificate (LDevID)
      carrying the domain information field which is used by the ACP to
      learn its address in the ACP and to derive and cryptographically
      assert its membership in the ACP domain.

   device:  A physical system, or physical node.

   Enrollment:  The process where a node presents identification (for
      example through keying material such as the private key of an
      IDevID) to a network and acquires a network specific identity and
      trust anchor such as an LDevID.

   EST:  "Enrollment over Secure Transport" ([RFC7030]).  IETF standard
      protocol for enrollment of a node with an LDevID.  BRSKI is based
      on EST.

   GRASP:  "Generic Autonomic Signaling Protocol".  An extensible
      signaling protocol required by the ACP for ACP neighbor discovery.
      The ACP also provides the "security and transport substrate" for
      the "ACP instance of GRASP" which is run inside GRASP".  This instance of GRASP runs across
      the ACP secure channels to support BRSKI and other future
      Autonomic Functions.  See [I-D.ietf-anima-grasp].

   IDevID:  An "Initial Device IDentity" X.509 certificate installed by
      the vendor on new equipment.  Contains information that
      establishes the identity of the node in the context of its vendor/
      manufacturer such as device model/type and serial number.  See
      [AR8021].  IDevID can not be used for the ACP because they are not
      provisioned by the owner of the network, so they can not directly
      indicate an ACP domain they belong to.

   in-band (management):  The type of management used predominantly in
      IP based networks, not leveraging an ->"out-of-band network" ().
      In in-band management, access to the managed equipment depends on
      the configuration of this equipment itself: interface, addressing,
      forwarding, routing, policy, security, management.  This
      dependency makes in-band management fragile because the
      configuration actions performed may break in-band management
      connectivity.  Breakage can not only be unintentional, it can
      simply be an unavoidable side effect of being unable to create
      configuration schemes where in-band management connectivity
      configuration is unaffected by Data-Plane configuration.  See also
      ->"(virtual) out-of-band network" ().

   Intent:  Northbound operator and automation facing interface  Policy language of an
      Autonomic Network autonomic network according to
      [I-D.ietf-anima-reference-model].

   loopback

   Loopback interface:  The conventional name for an internal IP
      interface to which addresses may be assigned, but which transmits
      no external traffic.

   LDevID:  A "Local Device IDentity" is an X.509 certificate installed
      during "enrollment".  The Domain Certificate used by the ACP is an
      LDevID.  See [AR8021].

   MIC:  "Manufacturer Installed Certificate".  Another word not used in
      this document to describe an IDevID.

   native interface:  Interfaces existing on a node without
      configuration of the already running node.  On physical nodes
      these are usually physical interfaces.  On virtual nodes their
      equivalent.

   node:  A system, e.g.: e.g., supporting the ACP according to this document.
      Can be virtual or physical.  Physical nodes are called devices.

   Node-ID:  The identifier of an ACP node inside that ACP.  It is the
      last 64 (see Section 6.10.3) or 78 bit (see xref target="Vlong"/>)
      of the ACP address.

   (virtual) out-of-band network:  An out-of-band network is a secondary
      network used to manage a primary network.  The equipment of the
      primary network is connected to the out-of-band network via
      dedicated management ports on the primary network equipment.
      Serial (console) management ports are most common, higher end
      network equipment also has ethernet ports dedicated only for
      management.  An out-of-band network provides management access to
      the primary network independent of the configuration state of the
      primary network.  One of the goals of the ACP is to provide this
      benefit of out-of-band networks virtually on the primary network
      equipment.  The ACP VRF acts as a virtual out of band network
      device providing configuration independent management access.  The
      ACP secure channels are the virtual links of the ACP virtual out-
      of-band network, meant to be operating independent of the
      configuration of the primary network.  See also ->"in-band
      (management)" ().

   RPL:  "IPv6 Routing Protocol for Low-Power and Lossy Networks".  The
      routing protocol used in the ACP.  See [RFC6550].

   MASA (service):  "Manufacturer Authorized Signing Authority".  A
      vendor/manufacturer or delegated cloud service on the Internet
      used as part of the BRSKI protocol.

   (ACP/ANI/BRSKI) Registrar:  An ACP registrar is an entity (software
      and/or person) that is orchestrating the enrollment of ACP nodes
      with the ACP domain certificate.  ANI nodes use BRSKI, so ANI
      registrars are also called BRSKI registrars.  For non-ANI ACP
      nodes, the registrar mechanisms are undefined by this document.
      See Section 6.10.7.  Renewal and other maintenance (such as
      revocation) of ACP domain certificates may be performed by other
      entities than registrars.  EST must be supported for ACP domain
      certificate renewal (see Section 6.1.3).  BRSKI is an extension of
      EST, so ANI/BRSKI registrars can easily support ACP domain
      certificate renewal in addition to initial enrollment.

   sUDI:  "secured Unique Device Identifier".  Another term not used in
      this document to refer to an IDevID.

   UDI:  "Unique Device Identifier".  In the context of this document
      unsecured identity information of a node typically consisting of
      at least device model/type and serial number, often in a vendor
      specific format.  See sUDI and LDevID.

   ULA: (Global ID prefix)  A "Unique Local Address" (ULA) is an IPv6
      address in the block fc00::/7, defined in [RFC4193].  It is the
      approximate IPv6 counterpart of the IPv4 private address
      ([RFC1918]).  The ULA Global ID prefix are the first 48 bit of a
      ULA address.  In this document it is abbreviated as "ULA prefix".

   (ACP) VRF:  The ACP is modelled modeled in this document as a "Virtual Routing
      and Forwarding" instance (VRF).  This means that it is based on a
      "virtual router" consisting of a separate IPv6 forwarding table to
      which the ACP virtual interfaces are attached and an associated
      separate IPv6 routing table.  Unlike the VRFs on MPLS/VPN-PE
      ([RFC4364]) or LISP XTR ([RFC6830]), the ACP VRF does not have any
      special "core facing" functionality or routing/
      mapping routing/mapping protocols
      shared across multiple VRFs.  In vendor products a VRF such as the
      ACP-VRF may also be referred to as a so called VRF-lite.

   (ACP) Zone:  An ACP zone is a connected region of the ACP where nodes
      derive from their non-aggregatable ACP address (identifier
      address) an aggregateable aggregatable ACP zone address (locator address).  See
      the definition of the ACP Zone Addressing Sub-Scheme
      (Section 6.10.3).  The complete definition of zones is subject to
      future work because this document does not describe the routing
      protocols details for aggregation of ACP zone addresses, but only
      their addressing scheme.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   [RFC2119]
   [RFC8174] when they appear in ALL CAPS.  When these words are not in
   ALL CAPS (such as "should" or "Should"), they have their usual
   English meanings, and are not to be interpreted as [RFC2119] [RFC8174] key
   words.

3.  Use Cases for an Autonomic Control Plane

3.1.  An Infrastructure for Autonomic Functions

   Autonomic Functions need a stable infrastructure to run on, and all
   autonomic functions should use the same infrastructure to minimize
   the complexity of the network.  This way, there is only need for a
   single discovery mechanism, a single security mechanism, and other
   processes that distributed functions require.

3.2.  Secure Bootstrap over a not configured Network

   Today, bootstrapping a new node typically requires all nodes between
   a controlling node such as an SDN controller ("Software Defined
   Networking", see [RFC7426]) and the new node to be completely and
   correctly addressed, configured and secured.  Bootstrapping and
   configuration of a network happens in rings around the controller -
   configuring each ring of devices before the next one can be
   bootstrapped.  Without console access (for example through an out of out-of-
   band network) it is not possible today to make devices securely
   reachable before having configured the entire network leading up to
   them.

   With the ACP, secure bootstrap of new devices can happen without
   requiring any configuration such as the transit connectivity to
   bootstrap further devices.  A new device can automatically be
   bootstrapped in a secure fashion and be deployed with a domain
   certificate.  This does not require any configuration on intermediate
   nodes, because they can communicate zero-touch and securely through
   the ACP.

3.3.  Data-Plane Independent Permanent Reachability

   Today, most critical control plane protocols and network management
   protocols are running in using the data-plane Data-Plane (global routing table) of the
   network.  This leads to undesirable dependencies between control and
   management plane on one side and the data-plane Data-Plane on the other: Only if
   the data-plane Data-Plane is operational, will the other planes work as
   expected.

   Data-plane

   Data-Plane connectivity can be affected by errors and faults, for
   example misconfigurations that make AAA (Authentication,
   Authorization and Accounting) servers unreachable or can lock an
   administrator out of a device; routing or addressing issues can make
   a device unreachable; shutting down interfaces over which a current
   management session is running can lock an admin irreversibly out of
   the device.  Traditionally only console access can help recover from
   such issues.

   Data-plane

   Data-Plane dependencies also affect applications in a NOC ("Network Network
   Operations Center") Center (NOC) such as SDN controller applications: Certain
   network changes are today hard to operate, because the change itself
   may affect reachability of the devices.  Examples are address or mask
   changes, routing changes, or security policies.  Today such changes
   require precise hop-by-hop planning.

   The ACP provides reachability that is independent of the data-plane Data-Plane
   (except for the dependency discussed in Section 6.12.2 which can be
   removed through future work), which allows the control plane and
   management plane to operate more robustly:

   o  For management plane protocols, the ACP provides the functionality
      of a "Virtual-out-of-band Virtual out of Band (VooB) channel", channel, by providing connectivity
      to all nodes regardless of their configuration or global routing
      table.

   o  For control plane protocols, the ACP allows their operation even
      when the data-plane Data-Plane is temporarily faulty, or during transitional
      events, such as routing changes, which may affect the control
      plane at least temporarily.  This is specifically important for
      autonomic service agents, which could affect data-plane Data-Plane
      connectivity.

   The document "Autonomic Network "Using Autonomic Control Plane for Stable Connectivity"
   [I-D.ietf-anima-stable-connectivity] Connectivity
   of Network OAM" [RFC8368] explains the this use cases case for the ACP in
   significantly more detail and explains how the ACP can be used in
   practical network operations.

4.  Requirements

   The Autonomic Control Plane has the following requirements:

   ACP1:  The ACP SHOULD provide robust connectivity: As far as
          possible, it should be independent of configured addressing,
          configuration and routing.  Requirements 2 and 3 build on this
          requirement, but also have value on their own.

   ACP2:  The ACP MUST have a separate address space from the data-
          plane. Data-
          Plane.  Reason: traceability, debug-ability, separation from
          data-plane,
          Data-Plane, security (can block easily at edge).

   ACP3:  The ACP MUST use autonomically managed address space.  Reason:
          easy bootstrap and setup ("autonomic"); robustness (admin
          can't mess things up so easily).  This document suggests to
          use using
          ULA addressing for this purpose ("Unique Local Address", see
          [RFC4193]).

   ACP4:  The ACP MUST be generic.  Usable by all the functions and
          protocols of the AN infrastructure. ANI.  Clients of the ACP MUST NOT be tied to
          a particular application or transport protocol.

   ACP5:  The ACP MUST provide security: Messages coming through the ACP
          MUST be authenticated to be from a trusted node, and SHOULD
          (very strong SHOULD) be encrypted.

   The

   Explanation for ACP4: In a fully autonomic network (AN), newly
   written ASA could potentially all communicate exclusively via GRASP
   with each other, and if that was assumed to be the only requirement
   against the ACP, it would not need to provide IPv6 layer connectivity
   between nodes, but only GRASP connectivity.  Nevertheless, because
   ACP also intends to support non-AN networks, it it is crucial to
   support IPv6 layer connectivity across the ACP to support any
   transport and application layer protocols.

   Th eACP operates hop-by-hop, because this interaction can be built on
   IPv6 link local addressing, which is autonomic, and has no dependency
   on configuration (requirement 1).  It may be necessary to have ACP
   connectivity across non-ACP nodes, for example to link ACP nodes over
   the general Internet.  This is possible, but introduces a dependency
   against stable/resilient routing over the non-ACP hops (see
   Section 8.2).

5.  Overview

   The Autonomic Control Plane is constructed in the following way (for
   details, see Section 6):

   1.  An ACP node creates a VRF ("Virtual Virtual Routing and Forwarding") Forwarding (VRF)
       instance, or a similar virtual context.

   2.  It determines, following a policy, a candidate peer list.  This
       is the list of nodes to which it should establish an Autonomic
       Control Plane.  Default policy is: To all link-layer adjacent
       nodes supporting ACP.

   3.  For each node in the candidate peer list, it authenticates that
       node and negotiates a mutually acceptable channel type.

   4.  For each node in the candidate peer list, it then establishes a
       secure tunnel of the negotiated type.  The resulting tunnels are
       then placed into the previously set up VRF.  This creates an
       overlay network with hop-by-hop tunnels.

   5.  Inside the ACP VRF, each node sets up a loopback interface with assigns its ULA IPv6 address. address to a
       Loopback interface assigned to the ACP VRF.

   6.  Each node runs a lightweight routing protocol, to announce
       reachability of the virtual addresses inside the ACP (see
       Section 6.12.5).

   Note:

   o  Non-autonomic NMS ("Network Management Systems") or SDN
      controllers have to be explicitly configured for connection into
      the ACP.

   o  Connecting over non-ACP Layer-3 clouds initially requires a tunnel
      between ACP nodes. explicit
      configuration.  See Section 8.2.  This may be automated in the
      future through auto discovery mechanisms across L3.

   o  None of the above operations (except explicit configured ones) are
      reflected in the configuration of the node.

   The following figure illustrates the ACP.

             ACP node 1                          ACP node 2
          ...................               ...................
   secure .                 .   secure      .                 .  secure
   tunnel :
   channel:  +-----------+  :   tunnel   channel     :  +-----------+  :  tunnel channel
   ..--------| ACP VRF   |---------------------| ACP VRF   |---------..
          : / \         / \   <--routing-->   / \         / \ :
          : \ /         \ /                   \ /         \ / :
   ..--------| loopback Loopback  |---------------------| loopback Loopback  |---------..
          :  | interface |  :               :  | interface |  :
          :  +-----------+  :               :  +-----------+  :
          :                 :               :                 :
          :   data-plane   Data-Plane    :...............:   data-plane   Data-Plane    :
          :                 :    link       :                 :
          :.................:               :.................:

                   Figure 1 1: ACP VRF and secure channels

   The resulting overlay network is normally based exclusively on hop-
   by-hop tunnels.  This is because addressing used on links is IPv6
   link local addressing, which does not require any prior set-up.  This
   way the ACP can be built even if there is no configuration on the
   node, or if the data-plane Data-Plane has issues such as addressing or routing
   problems.

6.  Self-Creation of an Autonomic Control Plane (ACP) (Normative)

   This section describes the components and steps to set up an
   Autonomic Control Plane (ACP), and highlights the key properties
   which make it "indestructible" against many inadvertent changes to
   the data-plane, Data-Plane, for example caused by misconfigurations.

   An ACP node can be a router, switch, controller, NMS host, or any
   other IP capable node.  Initially, it must have a its ACP domain
   certificate, as well as an (empty) ACP Adjacency Table (described in
   Section 6.2).  It then can start to discover ACP neighbors and build
   the ACP.  This is described step by step in the following sections:

6.1.  ACP Domain, Certificate and Network

   The ACP relies on group security.  An ACP domain is a group of nodes
   that trust each other to participate in ACP operations.  To establish
   trust, the each ACP member requires certificates: keying material: An ACP node MUST
   have keying
   material a certificate (LDevID) and a Trust Anchor (TA) consisting of a
   certificate (LDevID), with which it can (chain) used to sign the LDevID of all ACP domain
   members.  The LDevID is used to cryptographically assert its authenticate the
   membership of its owner node in the ACP domain and trust
   anchor(s) associated with that certificate with which it can verify to other ACP domain
   members, the TA is used to authenticate the ACP domain membership of
   other nodes (see Section 6.1.2).

   The certificate LDevID is called the ACP domain certificate, the trust anchor(s) are TA is the CA
   ("Certificate Authority")
   Certificate Authority (CA) of the ACP domain.

   The ACP does not mandate specific mechanisms by which this keying
   material is provisioned into the ACP node, it only requires the
   Domain information field as specified in Section 6.1.1 in its domain
   certificate as well as those of candidate ACP peers.  See
   Section 10.1 for more information about enrollment or provisioning
   options.

   Note: LDevID ("Local Device IDentification") is the term used to
   indicate a certificate that was provisioned by the owner of a node as
   opposed to IDevID ("Initial Device IDentifier") that may has been
   loaded on the node during manufacturing time.  Those IDevID do not
   include owner and deployment specific information to allows autonomic
   establishment of trust for the operations of an ACP domain (e.g.:
   between two ACP nodes without relying on any third party).

   This document uses the term ACP in many places where its the Autonomic
   Networking reference
   document documents [RFC7575] and
   [I-D.ietf-anima-reference-model] use the word autonomic.  This is
   done because those reference document documents consider (only) fully
   autonomic network networks and nodes, but support of ACP does not require
   support for other components of autonomic networks.  Therefore the
   word autonomic would might be irritating misleading to operators interested in only
   the ACP:

   [RFC7575] defines the term "Autonomic Domain" as a collection of
   autonomic nodes.  ACP nodes do not need to be fully autonomic, but
   when they are, then the ACP domain is an autonomic domain.  Likewise,
   [I-D.ietf-anima-reference-model] defines the term "Domain
   Certificate" as the certificate used in an autonomic domain.  The ACP
   domain certificate is that domain certificate when ACP nodes are
   (fully) autonomic nodes.  Finally, this document uses the term ACP
   network to refer to the network created by active ACP nodes in an ACP
   domain.  The ACP network itself can extend beyond ACP nodes through
   the mechanisms described in Section 8.1).

   The ACP domain certificate can and should be used for any
   authentication between ACP nodes where the required security is
   domain membership.  Section 6.1.2 defines this "ACP domain membership
   check".  The uses of this check that are standardized in this
   document are for the establishment of ACP secure channels
   (Section 6.6) and for ACP GRASP (Section 6.8.2).  Other uses are
   subject to future work, but it is recommended that it is the default
   security check for any end-to-end connections between ASA.  It is
   equally useable by other functions such as legacy OAM functions.

6.1.1.  Certificate Domain Information Field

   Information about the domain MUST be encoded in the domain
   certificate in a subjectAltName / rfc822Name field according to the
   following ABNF definition ([RFC5234]):

   [RFC Editor: Please substitute SELF in all occurences of rfcSELF in
   this document with the RFC number assigned to this document and
   remove this comment line]

     domain-information = local-part "@" domain
     local-part = key [ "." local-info ]
     key = "rfcSELF"
     local-info = [ acp-address ] [ "+" rsub extensions ]
     acp-address = 32hex-dig
     hex-dig = DIGIT / "a" / "b" / "c" / "d" / "e" / "f"
     rsub = [ domain-name ] ; empty if not used
     domain = domain-name
     routing-subdomain = [ rsub " ." ] domain
     domain-name = ; <domain> ; as of RFC1034, RFC 1034, section 3.5
     extensions = *( "+" extension )
     extension = ; future definition.
                 ; Must fit RFC5322 simple dot-atom format.

     Example:
     domain-information = rfcSELF+fd89b714f3db00000200000064000000
                          +area51.research@acp.example.com
     routing-subdomain = area51.research.acp.example.com

                Figure 2: ACP Domain Information Field ABNF

   "acp-address" MUST be the ACP address of the node.  It is optional to
   support variations of the ACP mechanisms, for example other means for
   nodes to assign ACP addresses to themselves.  Such methods are
   subject to future work though.

   Note: "acp-address" cannot use standard IPv6 address formats because
   it must match the simple dot-atom format of [RFC5322].  ":" are not
   allowed in that format.

   "domain" is used to indicate the ACP Domain across which all ACP
   nodes trust each other and are willing to build ACP channel to each
   other.  See Section 6.1.2.  Domain SHOULD be the FQDN of a domain
   owned by the operator assigning the certificate.  This is a simple
   method to ensure that the domain is globally unique and collision of
   ACP addresses would therefore only happen due to ULA hash collisions.
   If the operator does not own any FQDN, it should choose a string in
   FQDN format that intends to be equally unique.

   "routing-subdomain" is the autonomic subdomain that is used to
   calculate the hash for the ULA prefix Global ID of the ACP address of the
   node.  "rsub" is optional; its syntax is defined in this document,
   but its semantics are for further study.  Understanding the benefits
   of using rsub may depend on the results of future work on enhancing
   routing for the ACP.  When "rsub" is not used, "routing-subdomain" is
   the same as "domain". "rsub" needs to be in the "local-part"; it
   could not syntactically be separated from "domain-name" if "domain"
   is just a domain name.  It also makes it easier for domain name to be
   a valid e-mail target.

   The optional "extensions" field is used for future extensions to this
   specification.  It MUST be ignored if present and not understood.

   In this specification, the "acp-address" field is REQUIRED, but
   future variations (see Section 10.11) may use local information to
   derive the ACP address.  In this case, "acp-address" could be empty.
   Such a variation would be indicated by an appropriate "extension".
   If "acp-address" is empty, and "rsub" is empty too, the "local-part"
   will have the format "rfcSELF + + extension(s)".  The two plus
   characters are necessary so the node can unambiguously parse that
   both "acp-address" and "rsub" are empty.

   Note that the maximum size of "domain-information" is 254 characters
   and the maximum size of node-info is 64 characters according to
   [RFC5280] that is referring to [RFC2821] (superseded by [RFC5321]).

   The subjectAltName / rfc822Name encoding of the ACP domain name and
   ACP address is used for the following reasons:

   o  There are a wide range of pre-existing protocols/services where
      authentication with  It should be possible to share the LDevID is desirable.  Enrolling and
      maintaining separate LDevIDs for each of these protocols/services
      is often undesirable overhead. with other uses beside
      the ACP.  Therefore, the information element required for the ACP in the domain certificate
      should be encoded
      in a way so that it minimizes the possibility of creating
      incompatibilities with such other uses beside the authentication
      for the ACP. uses.

   o  The elements in the LDevID required information for the ACP should not cause incompatibilities
      with any pre-existing ASN.1 software potentially
      in use in those other pre-existing SW systems. software.  This eliminates the use
      introduction of a novel information elements element because those that could
      require extensions to those such pre-existing ASN.1 parsers.

   o  subjectAltName / rfc822Name is a pre-existing element that must be
      supported by all existing ASN.1 parsers for LDevID.

   o  The elements in the LDevID element required for the ACP should also not be misinterpreted by
      any pre-existing protocol/service that might use other uses of the LDevID.  If the elements element used for the ACP are is
      interpreted by other protocols/services, then uses, the impact should be benign.

   o  Using an IP address format encoding could result in non-benign
      misinterpretation of the domain information field; other protocol/
      services uses
      unaware of the ACP could try to do something with the ACP address
      that would fail to work correctly.  For example, the address could
      be interpreted to be an address of the node in a VRF
      other than which does not belong
      to the ACP VRF.

   o  At minimum, both the AN domain name and the non-domain name
      derived part of the ACP address need to be encoded in one or more
      appropriate fields of the certificate, so there are not many
      alternatives with pre-existing fields where the only possible
      conflicts would likely be beneficial.

   o  rfc822Name encoding is quite flexible.  We choose to encode the
      full ACP address AND the domain name with sub part into a single
      rfc822Name information element it, so that it is easier to
      examine/use the "domain information field".

   o  The format of the rfc822Name is chosen so that an operator can set
      up a mailbox called   rfcSELF@<domain> that would receive emails
      sent towards the rfc822Name of any node inside a domain.  This is
      possible because in many modern mail systems, components behind a
      "+" character are considered part of a single mailbox.  In other
      words, it is not necessary to set up a separate mailbox for every
      ACP node, but only one for the whole domain.

   o  In result, if any unexpected use of the ACP addressing information
      in a certificate happens, it is benign and detectable: it would be
      mail to that mailbox.

   See section 4.2.1.6 of [RFC5280] for details on the subjectAltName
   field.

6.1.2.  ACP domain membership check

   The following points constitute the ACP domain membership check:

   o  The peer certificate is valid as proven by the security
      associations protocol exchange.

   o  The peers peer's certificate is signed by one of the trust anchors
      associated with the ACP domain certificate.

   o  If the node certificates indicate indicates a CDP (or OCSP) Certificate Revocation List
      (CRL) Distribution Point (CDP) ([RFC5280], section 4.2.1.13) or
      Online Certificate Status Protocol (OCSP) responder ([RFC5280],
      section 4.2.2.1), then the peer's certificate must be valid
      according to those criteria. e.g.: criteria: An OCSP check for the peers
      certificate across the ACP must succeed or the peer certificate
      must not be listed in the CRL retrieved from the CDP.

   o  The peers certificate has a syntactically valid domain information
      field (subjectAltName / rfc822Name) and the domain name in that
      peers domain information field is the same as in this ACP node
      certificate.  Note that future Intent rules may modify this.  See
      Section 10.7. 10.10.

6.1.3.  Certificate Maintenance

   ACP nodes MUST support certificate renewal via EST ("Enrollment over
   Secure Transport", see [RFC7030]) and MAY support other mechanisms.
   An ACP network MUST have at least one ACP node supporting EST server
   functionality across the ACP so that EST renewal is useable.  The
   mechanism by which

   ACP nodes SHOULD be able to remember the EST server from which they
   last renewed their ACP domain certificate was initially provisioned and SHOULD provide a mechanism to store the URL of one
   ability for this remembered EST server to also be set by the ACP
   Registrar (see Section 6.10.7) that initially enrolled the ACP device
   with its ACP domain certificate.  When BRSKI (see
   [I-D.ietf-anima-bootstrapping-keyinfra]) is used, the ACP address into of
   the node for later renewal.  This server does
   not have to BRSKI registrar from the BRSKI TLS connection SHOULD be
   remembered and used for the same next renewal via EST if that registrar
   also announces itself as the one performing the initial certificate
   enrolment. an EST server via GRASP (see next section)
   on its ACP address.

6.1.3.1.  GRASP objective for EST server

   ACP nodes that are EST servers MUST announce their service via GRASP
   in the ACP through M_FLOOD messages: messages.  See [I-D.ietf-anima-grasp],
   section 2.8.11 for the definition of this message type:

        Example:

        [M_FLOOD, 12340815, h'fd89b714f3db0000200000064000001', 210000,
            ["SRV.est", 4, 255 ],
            [O_IPv6_LOCATOR,
                 h'fd89b714f3db0000200000064000001', TCP, 80]
        ]

                      Figure 3: GRASP SRV.est example

   The formal CDDL definition is: of the objective in Concise data definition
   language (CDDL) (see [I-D.ietf-cbor-cddl]) is as follows:

    flood-message = [M_FLOOD, session-id, initiator, ttl,
                     +[objective, (locator-option / [])]]

    objective = ["SRV.est", objective-flags, loop-count,
                                           objective-value]

    objective-flags = sync-only  ; as in GRASP spec
    sync-only =  4               ; M_FLOOD only requires synchronization
    loop-count      = 255        ; recommended
    objective-value =            ; Not used (yet)

                    Figure 4: GRASP SRV.est definition

   The objective value "SRV.est" indicates that the objective is an
   [RFC7030] compliant EST server because "est" is an [RFC6335]
   registered service name for [RFC7030].  Future backward compatible
   extensions/alternatives to [RFC7030] may be indicated through
   objective-value.  Future non-backward compatible certificate renewal
   options must use a different objective-name.

   The M_FLOOD message MUST be sent periodically.  The default SHOULD be
   60 seconds, the value SHOULD be operator configurable.  It must  The frequency
   of sending MUST be so
   high such that the aggregate amount of periodic
   M_FLOODs from all flooded
   objectives flooding sources causes only negligible traffic
   across the ACP.  The ttl parameter SHOULD be 3.5 times the period so
   that up to three consecutive messages can be dropped before
   considering an announcement expired.  In the example above, the ttl
   is 210000 msec, 3.5 times 60 seconds.

   Domain certificates SHOULD by default be renewed 50% into their
   lifetime.  When a service announcer using
   these parameters unexpectedly dies immediately after sending the
   M_FLOOD, receivers would consider it expired 210 seconds later.  When
   a receiver tries to connect to this dead service before this timeout,
   it will experience a failing connection and use that as an indication
   that the service is dead and select another instance of the same
   service instead.

6.1.3.2.  Renewal

   When performing renewal, the node SHOULD attempt to connect to the
   remembered EST server.  If that fails, it SHOULD attempt to connect
   to an EST server(s) server learned via GRASP.  The server with which
   certificate renewal succeeds SHOULD be remembered for the next
   renewal.

   Remembering the last renewal server and preferring it provides
   stickiness which can help diagnostics.  It also provides some
   protection against off-path compromised ACP members announcing bogus
   information into GRASP.

   The ACP node MUST support CRLs ("Certificate Revocation Lists") via
   HTTPs from one or more CDPs ("CRL Distribution Points").  These CDPs
   MUST be indicated in the Domain Certificate when used.  If the CDP
   URL uses an IPv6 ULA, the ACP node will try to reach it via the ACP.
   In that case the ACP address in the domain certificate of the CDP as
   learned by the ACP node during the HTTPs TLS handshake SHOULD match
   that ULA address in the HTTPs URL.

   Renewal of certificates SHOULD start after less than 50% of the
   domain certificate lifetime so that network operations has ample time
   to investigate and resolve any problems that cause causes a node to not
   renew its domain certificate in time - and to allow prolonged periods
   of running parts of a network disconnected from any CA.

6.1.3.3.  Certificate lifetime should Revocation Lists (CRLs)

   The ACP node SHOULD support Certificate Revocation Lists (CRL) via
   HTTPs from one or more CRL Distribution Points (CDPs).  The CDP(s)
   MUST be set indicated in the Domain Certificate when used.  If the CDP
   URL uses an IPv6 address (ULA address when using the addressing rules
   specified in this document), the ACP node will connect to be as short as feasible.  Given
   how certificate renewal is fully automated the CDP via ACP and EST,
   the
   primarily limiting factor for shorter certificate lifetimes (than ACP.  If the
   typical one year) is load on CDP URL uses an IPv6 address (ULA address when using
   the addressing rules specified in this document), the EST server(s) and CA.  It is
   therefore recommended that ACP domain certificates are managed node will
   connect to the CDP via the ACP.  If the CDP uses a
   CA chain where domain name, the assigning CA has enough performance
   ACP node will connect to manage the CDP via the Data-Plane.

   It is common to use domain names for CDP(s), but there is no
   requirement for the ACP to support DNS.  Any DNS lookup in the Data-
   Plane is not only a possible security issue, but it would also not
   indicate whether the resolved address is meant to be reachable across
   the ACP.  Therefore, the use of an IPv6 address versus the use of a
   DNS name doubles as an indicator whether or not to reach the CDP via
   the ACP.

   A CDP can be reachable across the ACP either by running it on a node
   with ACP or by connecting its node via an ACP connect interface (see
   Section 8.1).  The CDP SHOULD use an ACP domain certificate for its
   HTTPs connections.  The connecting ACP node SHOULD verify that the
   CDP certificate used during the HTTPs connection has the same ACP
   address as indicated in the CDP URL of the nodes ACP domain
   certificate

6.1.3.4.  Lifetimes

   Certificate lifetime may be set to shorter lifetimes than customary
   (1 year) because certificate renewal is fully automated via ACP and
   EST.  The primary limiting factor for shorter certificate lifetimes
   is load on the EST server(s) and CA.  It is therefore recommended
   that ACP domain certificates are managed via a CA chain where the
   assigning CA has enough performance to manage short lived
   certificates.  See also Section 10.3.4 for discussion about an
   example setup achieving this.

   When certificate lifetimes are sufficiently short, such as few hours,
   certificate revocation may not be necessary, allowing to simplify the
   overall certificate maintenance infrastructure.

   See Section 10.1 for further optimizations of certificate maintenance
   when BRSKI can be used ("Bootstrapping Remote Secure Key
   Infrastructures", see [I-D.ietf-anima-bootstrapping-keyinfra]).

6.2.

6.1.3.5.  Re-enrollment

   An ACP Adjacency Table

   To know to which nodes to establish an node may determine that its ACP channel, every domain certificate has
   expired, for example because the ACP node
   maintains an adjacency table.  The adjacency table contains
   information about adjacent was powered down or
   disconnected longer than its certificate lifetime.  In this case, the
   ACP nodes, at node SHOULD convert to a minimum: Node-ID,
   interface on which neighbor was discovered (by GRASP as explained
   below), link-local IPv6 address role of neighbor on that interface,
   certificate (including domain information field).  An a re-enrolling candidate ACP
   node.

   In this role, the node MUST does maintain this adjacency table up the trust anchor and certificate
   chain associated with its ACP domain certificate exclusively for the
   purpose of re-enrollment, and attempts (or waits) to date.  This table is get re-enrolled
   with a new ACP certificate.  The details depend on the mechanisms/
   protocols used by the ACP registrars.

   Please refer to
   determine to which neighbor an Section 6.10.7 for explanations about ACP connection registrars
   and vouchers as used in the following text.

   When BRSKI is established.

   Where used (aka: on ACP nodes that are ANI nodes), the next re-
   enrolling candidate ACP node is not directly adjacent, would attempt to enroll like a candidate
   ACP node (BRSKI pledge), but instead of using the information ACP nodes IDevID,
   it SHOULD first attempt to use its ACP domain certificate in the adjacency table can be supplemented by configuration.  For
   example, the node-ID and IP address could be configured.
   BRSKI TLS authentication.  The adjacency table BRSKI registrar MAY contain information about honor this
   certificate beyond its expiration date purely for the validity and
   trust purpose of re-
   enrollment.  Using the adjacent ACP node's certificate.  However, subsequent
   steps MUST always start with authenticating the peer.

   The adjacency table contains information about adjacent ACP nodes in
   general, independently of their domain and trust status.  The next
   step determines certificate allows the BRSKI
   registrar to which of those ACP learn that nodes an ACP connection should
   be established.

   Interaction between ACP and other autonomic elements like GRASP (see
   below) or ASAs should be via an API domain information field, so that allows (appropriately access
   controlled) read/write access to
   the BRSKI registrar can re-assign the same ACP Adjacency Table.
   Specification of such an API is subject address information to future work.

6.3.  Neighbor Discovery with DULL GRASP

   The
   the ACP uses one instance of DULL GRASP ( See section 3.5.2.2 of
   [I-D.ietf-anima-grasp] for its formal definition) for every physical
   L2 subnet node in the new ACP domain certificate.

   If the BRSKI registrar denies the use of the old ACP node to discover physically adjacent domain
   certificate, the re-enrolling candidate ACP neighbors.  Native interfaces (e.g.: physical interfaces on
   physical nodes) SHOULD be brought up automatically enough so that ACP
   discovery can be performed and any native interfaces node MUST re-attempt re-
   enrollment using its IDevID as defined in BRSKI during the TLS
   connection setup.

   Both when the BRSKI connection is attempted with the old ACP
   neighbors can then be brought into domain
   certificate or the IDevID, the re-enrolling candidate ACP even if node SHOULD
   authenticate the interface is
   otherwise not configured.  Reception of packets BRSKI registrar during TLS connection setup based on such otherwise not
   configured interfaces MUST be limited so that at first only IPv6
   link-local address assignment (SLAAC) and DULL GRASP works and then
   its existing trust anchor/certificate chain information associated
   with its old ACP certificate.  The re-enrolling candidate ACP node
   SHOULD only request a voucher from the following ACP secure channel setup packets - but not any
   other unnecessary traffic (e.g.: no BRSKI registrar when this
   authentication fails during TLS connection setup.

   When other link-local IPv6 transport
   stack responders mechanisms than BRSKI are used for example).

   Note that ACP domain certificate
   enrollment, the use principles of the IPv6 link-local multicast address
   (ALL_GRASP_NEIGHBORS) implies re-enrolling candidate ACP node are
   the need to use MLD ([RFC3810]) same.  The re-enrolling candidate ACP node attempts to
   announce
   authenticate any ACP registrar peers during re-enrollment protocol/
   mechanisms via its existing certificate chain/trust anchor and
   provides its existing ACP domain certificate and other identification
   (such as the desire IDevID) as necessary to receive packets for the registrar.

   Maintaining existing trust anchor information is especially important
   when enrollment mechanisms are used that address.  Otherwise
   DULL GRASP could fail unlike BRSKI do not leverage
   a voucher mechanism to operate correctly in authenticate the presence ACP registrar and where
   therefore the injection of MLD
   snooping, non-ACP enabled L2 switches - because those would stop
   forwarding DULL GRASP packets.  Switches not certificate failures could otherwise make
   the ACP node easily attackable remotely.

   When using BRSKI or other protocol/mechanisms supporting MLD snooping
   simply need to operate as pure L2 bridges for IPv6 multicast packets vouchers,
   maintaining existing trust anchor information allows for DULL GRASP re-
   enrollment of expired ACP certificates to work. be more lightweight,
   especially in environments where repeated acquisition of vouchers
   during the lifetime of ACP discovery SHOULD NOT nodes may be enabled by default on non-native
   interfaces.  In particular, operationally expensive or
   otherwise undesirable.

6.1.3.6.  Failing Certificates

   An ACP discovery MUST NOT run inside domain certificate is called failing in this document, if/when
   the ACP
   across node can determine that it was revoked (or explicitly not
   renewed), or in the absence of such explicit local diagnostics, when
   the ACP virtual interfaces.  See Section 10.3 for further, non-
   normative suggestions how node fails to enable/disable connect to other ACP at node and interface
   level.  See Section 8.2.2 for more details about tunnels (typical
   non-native interfaces).  See Section 7 for how nodes in the same ACP
   domain using its ACP certificate.  For connection failures to
   determine the ACP domain certificate as the culprit, the peer should
   pass the domain membership check (Section 6.1.2) and other reasons
   for the connection failure can be extended
   on devices operating (also) as L2 bridges.

   Note: If an excluded because of the connection
   error diagnostics.

   This type of failure can happen during setup/refresh of a secure ACP node also implements BRSKI (see Section 10.1) then
   channel connections or any other use of the above considerations also apply ACP domain certificate,
   such as for the TLS connection to discovery an EST server for BRSKI.  Each
   DULL instance the renewal of GRASP set up for
   the ACP is then also used domain certificate.

   Example reasons for failing certificates that the
   discovery of a bootstrap proxy via BRSKI when the ACP node does not have
   a can only
   discover through connection failure are that the domain certificate.  Discovery certificate
   or any of its signing certificates could have been revoked or may
   have expired, but the ACP neighbors happens node can not self-diagnose this condition
   directly.  Revocation information or clock synchronization may only when
   be available across the ACP, but the ACP node does have can not build ACP
   secure channels because ACP peers reject the ACP node's domain
   certificate.  The node therefore never needs

   ACP nodes SHOULD support the option to discover both a bootstrap proxy and determines whether its ACP neighbor at
   certificate is failing, and when it does, put itself into the same time.

   An role of
   a re-enrolling candidate ACP node announces itself as explained above
   (Section 6.1.3.5).

6.2.  ACP Adjacency Table

   To know to potential which nodes to establish an ACP peers by use channel, every ACP node
   maintains an adjacency table.  The adjacency table contains
   information about adjacent ACP nodes, at a minimum: Node-ID
   (identifier of the
   "AN_ACP" objective. node inside the ACP, see Section 6.10.3 and
   Section 6.10.5), interface on which neighbor was discovered (by GRASP
   as explained below), link-local IPv6 address of neighbor on that
   interface, certificate (including domain information field).  An ACP
   node MUST maintain this adjacency table up to date.  This table is a synchronization objective intended
   used to
   be flooded determine to which neighbor an ACP connection is established.

   Where the next ACP node is not directly adjacent (i.e., not on a single link using
   connected to this node), the GRASP Flood Synchronization
   (M_FLOOD) message.  In accordance with information in the design of adjacency table can
   be supplemented by configuration.  For example, the Flood
   message, a locator consisting of a specific link-local IP address, IP
   protocol number Node-ID and port number will IP
   address could be distributed with configured.

   The adjacency table MAY contain information about the flooded
   objective.  An example validity and
   trust of the message is informally:

         Example:

         [M_FLOOD, 12340815, h'fe80000000000000c0011001FEEF0000, 180000,
             ["AN_ACP", 4, 1, "IKEv2" ],
             [O_IPv6_LOCATOR,
                  h'fe80000000000000c0011001FEEF0000, UDP, 15000]
             ["AN_ACP", 4, 1, "dTLS" ],
             [O_IPv6_LOCATOR,
                  h'fe80000000000000c0011001FEEF0000, UDP, 17000]
         ] adjacent ACP node's certificate.  However, subsequent
   steps MUST always start with authenticating the peer.

   The formal CDDL definition is:

           flood-message = [M_FLOOD, session-id, initiator, ttl,
                            +[objective, (locator-option / [])]]

           objective = ["AN_ACP", objective-flags, loop-count,
                                                  objective-value]

           objective-flags = sync-only ; as adjacency table contains information about adjacent ACP nodes in the GRASP specification
           sync-only =  4    ; M_FLOOD only requires synchronization
           loop-count = 1    ; limit to link-local operation
           objective-value = method
           method = "IKEv2" / "dTLS"  ; or future methods
   general, independently of their domain and trust status.  The objective-flags field is set next
   step determines to indicate synchronization.

   The loop-count is fixed at 1 since this is a link-local operation.

   In the above (recommended) example the period of sending which of the
   objective could those ACP nodes an ACP connection should
   be 60 seconds the indicated ttl of 180000 msec means established.

   Interaction between ACP and other autonomic elements like GRASP (see
   below) or ASAs should be via an API that allows (appropriately access
   controlled) read/write access to the objective would be cached by ACP nodes even when two out Adjacency Table.
   Specification of
   three messages are dropped such an API is subject to future work.

6.3.  Neighbor Discovery with DULL GRASP

   [RFC Editor: GRASP draft is in transit.

   The session-id RFC editor queue, waiting for
   dependencies, including ACP.  Please ensure that references to I-
   D.ietf-anima-grasp that include section number references (throughout
   this document) will be updated in case any last-minute changes in
   GRASP would make those section references change.

   DULL GRASP is a random number used limited subset of GRASP intended to operate across an
   insecure link-local scope.  See section 2.5.2 of
   [I-D.ietf-anima-grasp] for loop prevention
   (distinguishing a message from a prior its formal definition.  The ACP uses one
   instance of the same message).
   In DULL this field is irrelevant but must still be set according to
   the GRASP specification.

   The originator MUST be the IPv6 link local address for every L2 interface of the originating ACP node to
   discover link level adjacent candidate ACP neighbors.  Unless
   modified by policy as noted earlier (Section 5 bullet point 2.),
   native interfaces (e.g., physical interfaces on the sending interface.

   The 'objective-value' parameter is a string indicating the secure
   channel protocol available at the specified or implied locator.

   The locator-option is optional physical nodes)
   SHOULD be initialized automatically enough, so that ACP discovery can
   be performed and only required when any native interfaces with ACP neighbors can then be
   brought into the secure
   channel protocol is not offered at a well-defined port number, or ACP even if
   there is no well-defined port number.

   "IKEv2" is the abbreviation for "Internet Key Exchange protocol
   version 2", as defined in [RFC7296].  It interface is the main protocol used by
   the Internet IP security architecture ("IPsec", see [RFC4301]).  We
   therefore use the term "IKEv2" and otherwise not "IPsec" in the
   configured.  Reception of packets on such otherwise not configured
   interfaces MUST be limited so that at first only IPv6 State Less
   Address Auto Configuration (SLAAC - [RFC4862]) and DULL GRASP
   definitions work
   and example above.  "IKEv2" has a well-defined port
   number 500, but in the above example, then only the candidate ACP neighbor is
   offering following ACP secure channel negotiation via IKEv2 on port 15000 (for setup packets - but
   not any other unnecessary traffic (e.g., no other link-local IPv6
   transport stack responders for example).

   Note that the sake use of creating a non-standard example).

   If a locator is included, it MUST be an O_IPv6_LOCATOR, and the IPv6 link-local multicast address MUST be
   (ALL_GRASP_NEIGHBORS) implies the same as need to use Multicast Listener
   Discovery Version 2 (MLDv2, see [RFC3810]) to announce the initiator address (these are desire to
   receive packets for that address.  Otherwise DULL
   requirements GRASP could fail to minimize third party DoS attacks).

   The secure channel methods defined
   operate correctly in this document use the objective
   values presence of "IKEv2" and "dTLS".  There is no distinction between IKEv2
   native and GRE-IKEv2 MLD snooping, non-ACP enabled L2
   switches - because this is purely negotiated via IKEv2.

   A node that supports more than one secure channel protocol method
   needs those would stop forwarding DULL GRASP packets.
   Switches not supporting MLD snooping simply need to flood multiple versions of the "AN_ACP" objective so that
   each method can operate as pure
   L2 bridges for IPv6 multicast packets for DULL GRASP to work.

   ACP discovery SHOULD NOT be accompanied enabled by its own locator-option.  This can
   use a single GRASP M_FLOOD message as shown in above example.

   Note that a default on non-native
   interfaces.  In particular, ACP discovery MUST NOT run inside the ACP
   across ACP virtual interfaces.  See Section 10.5 for further, non-
   normative suggestions on how to enable/disable ACP at node serving both and
   interface level.  See Section 8.2.2 for more details about tunnels
   (typical non-native interfaces).  See Section 7 for how ACP should be
   extended on devices operating (also) as L2 bridges.

   Note: If an ACP node and also implements BRSKI Join Proxy may
   choose to distribute the "AN_ACP" objective and the respective BRSKI
   in the same M_FLOOD message, since GRASP allows multiple objectives
   in one message.  This may be impractical though if enroll its ACP and BRSKI
   operations are implemented via separate software modules / ASAs.

   The result of domain
   certificate (see Section 10.1 for a summary), then the above
   considerations also apply to GRASP discovery is the IPv6 link-local address for BRSKI.  Each DULL
   instance of the
   neighbor as well as its supported secure channel protocols (and non-
   standard port they are running on).  It is stored in the GRASP set up for ACP
   Adjacency Table, see Section 6.2 which is then drives also used for the further
   building discovery
   of a bootstrap proxy via BRSKI when the node does not have a domain
   certificate.  Discovery of ACP neighbors happens only when the node
   does have the certificate.  The node therefore never needs to that neighbor.

6.4.  Candidate
   discover both a bootstrap proxy and ACP Neighbor Selection neighbor at the same time.

   An ACP node must determine announces itself to which other potential ACP nodes in peers by use of the adjacency
   table it should build an ACP connection.
   "AN_ACP" objective.  This is based a synchronization objective intended to
   be flooded on a single link using the
   information in the ACP Adjacency table.

   The ACP is by default established exclusively between nodes in GRASP Flood Synchronization
   (M_FLOOD) message.  In accordance with the
   same domain.  This includes all routing subdomains.  Section 10.7
   explains how ACP connections across multiple routing subdomains are
   special.

   Future extensions to this document including Intent can change this
   default behavior.  Examples include:

   o  Build design of the ACP across all domains that have Flood
   message, a common parent domain.
      For example ACP nodes with domain "example.com", nodes locator consisting of
      "example.com", "access.example.com", "core.example.com" a specific link-local IP address, IP
   protocol number and
      "city.core.example.com" could all establish one single ACP.

   o  ACP connections across domains port number will be distributed with different CA (certificate
      authorities) could establish a common ACP by installing the
      alternate domains' CA into flooded
   objective.  An example of the trusted anchor store.  This message is an
      executive management action that could easily be accomplished
      through the control channel created by the ACP.

   Since Intent informally:

         Example:

         [M_FLOOD, 12340815, h'fe80000000000000c0011001FEEF0000, 210000,
             ["AN_ACP", 4, 1, "IKEv2" ],
             [O_IPv6_LOCATOR,
                  h'fe80000000000000c0011001FEEF0000, UDP, 15000]
             ["AN_ACP", 4, 1, "DTLS" ],
             [O_IPv6_LOCATOR,
                  h'fe80000000000000c0011001FEEF0000, UDP, 17000]
         ]

                      Figure 5: GRASP AN_ACP example

   The formal CDDL definition is:

           flood-message = [M_FLOOD, session-id, initiator, ttl,
                            +[objective, (locator-option / [])]]

           objective = ["AN_ACP", objective-flags, loop-count,
                                                  objective-value]

           objective-flags = sync-only ; as in the GRASP specification
           sync-only =  4    ; M_FLOOD only requires synchronization
           loop-count = 1    ; limit to link-local operation
           objective-value = method
           method = "IKEv2" / "DTLS"  ; or future methods

                     Figure 6: GRASP AN_ACP definition

   The objective-flags field is transported over set to indicate synchronization.

   The loop-count is fixed at 1 since this is a link-local operation.

   In the ACP, above example the first ACP connection a
   node establishes is always following RECOMMENDED period of sending of the default behavior.  See
   Section 10.7 for more details.
   objective is 60 seconds.  The result indicated ttl of 210000 msec means that
   the candidate objective would be cached by ACP neighbor selection process nodes even when two out of three
   messages are dropped in transit.

   The session-id is a list random number used for loop prevention
   (distinguishing a message from a prior instance of adjacent or configured autonomic neighbors to which an ACP channel
   should the same message).
   In DULL this field is irrelevant but must still be established.  The next step begins that channel
   establishment.

6.5.  Channel Selection

   To avoid attacks, initial discovery of candidate ACP peers cannot
   include any non-protected negotiation.  To avoid re-inventing and
   validating security association mechanisms, set according to
   the next step after
   discovering GRASP specification.

   The originator MUST be the IPv6 link local address of a candidate neighbor can only be to try
   first to establish a security association with that neighbor using a
   well-known security association method.

   At this time in the lifecycle of originating
   ACP nodes, it is unclear whether it
   is feasible to even decide node on the sending interface.

   The 'objective-value' parameter is a single MTI (mandatory to implement)
   security association string indicating the secure
   channel protocol across all ACP nodes:

   From available at the use-cases it seems clear that not all type of ACP nodes can
   or need to connect directly to each other or are able to support specified or
   prefer all possible mechanisms.  For example, code space limited IoT
   devices may only support dTLS ("datagram Transport Layer Security
   version 1.2", see [RFC6347]) because that code exists already on them
   for end-to-end security, but low-end in-ceiling L2 switches may only
   want to support MacSec because that implied locator.

   The locator-option is also supported in their chips.
   Only a flexible gateway device may need to support both of these
   mechanisms optional and potentially more.

   To support extensible only required when the secure
   channel protocol selection without is not offered at a
   single common MTI protocol, ACP nodes must try all well-defined port number, or if
   there is no well-defined port number.

   "IKEv2" is the ACP secure
   channel protocols it supports abbreviation for "Internet Key Exchange protocol
   version 2", as defined in [RFC7296].  It is the main protocol used by
   the Internet IP security architecture ("IPsec", see [RFC4301]).  We
   therefore use the term "IKEv2" and that are feasible because not "IPsec" in the
   candidate ACP neighbor also announced them via its AN_ACP GRASP
   parameters (these are called
   definitions and example above.  "IKEv2" has a well-defined port
   number 500, but in the "feasible" above example, the candidate ACP neighbor is
   offering ACP secure channel
   protocols).

   To ensure that negotiation via IKEv2 on port 15000 (for
   the selection sake of the secure channel protocols always
   succeeds in creating a predictable fashion without blocking, the following
   rules apply:

   An ACP node may choose to attempt initiate the different feasible ACP
   secure channel protocols it supports according to its local policies
   sequentially or in parallel, but non-standard example).

   If a locator is included, it MUST support acting be an O_IPv6_LOCATOR, and the IPv6
   address MUST be the same as a
   responder the initiator address (these are DULL
   requirements to all of them minimize third party DoS attacks).

   The secure channel methods defined in parallel.

   Once this document use the first objective
   values of "IKEv2" and "DTLS".  There is no distinction between IKEv2
   native and GRE-IKEv2 because this is purely negotiated via IKEv2.

   A node that supports more than one secure channel protocol succeeds, method
   needs to flood multiple versions of the two peers know "AN_ACP" objective so that
   each other's certificates because it must method can be used accompanied by all secure
   channel protocols for mutual authentication.  The node with the lower
   Node-ID its own locator-option.  This can
   use a single GRASP M_FLOOD message as shown in the Figure 5.

   Note that a node serving both as an ACP address becomes Bob, node and BRSKI Join Proxy may
   choose to distribute the one with "AN_ACP" objective and the higher Node-
   ID respective BRSKI
   in the certificate Alice.

   Bob becomes passive, he does not attempt to further initiate same M_FLOOD message, since GRASP allows multiple objectives
   in one message.  This may be impractical though if ACP
   secure channel protocols with Alice and does not consider it to be an
   error when Alice closes secure channels.  Alice becomes BRSKI
   operations are implemented via separate software modules / ASAs.

   The result of the active
   party, continues to attempt setting up discovery is the IPv6 link-local address of the
   neighbor as well as its supported secure channel protocols with
   Bob until she arrives at (and non-
   standard port they are running on).  It is stored in the best one from her view that also works
   with Bob.

   For example, originally Bob could have been ACP
   Adjacency Table, see Section 6.2 which then drives the initiator further
   building of one the ACP
   secure channel protocol to that Bob prefers and neighbor.

6.4.  Candidate ACP Neighbor Selection

   An ACP node must determine to which other ACP nodes in the security association
   succeeded. adjacency
   table it should build an ACP connection.  This is based on the
   information in the ACP Adjacency table.

   The roles of Bob and Alice ACP is by default established exclusively between nodes in the
   same domain.  This includes all routing subdomains.  Section 10.10
   explains how ACP connections across multiple routing subdomains are then assigned.  At
   special.

   Future extensions to this
   stage, document including Intent can change this
   default behavior.  Examples include:

   o  Build the protocol may not even ACP across all domains that have completed negotiating a common
   security profile.  The protocol could for parent domain.
      For example could have been
   IPsec via IKEv2 ("IP security", see [RFC4301] ACP nodes with domain "example.com", nodes of
      "example.com", "access.example.com", "core.example.com" and "Internet Key
   Exchange protocol version 2", see [RFC7296].  It is now up to Alice
   to decide how to proceed.  Even if the IPsec connecting determined a
   working profile with Bob, Alice might prefer some other secure
   protocol (e.g.: dTLS) and try to set that up
      "city.core.example.com" could all establish one single ACP.

   o  ACP connections across domains with Bob.  If different Certificate
      Authorities (CA) could establish a common ACP by installing the
      alternate domains' CA into the trusted anchor store.  This is an
      executive management action that
   succeeds, she would close could easily be accomplished
      through the IPsec connection.  If no better
   protocol attempt succeeds, she would keep control channel created by the IPsec connection.

   All this negotiation ACP.

   Since Intent is in transported over the context ACP, the first ACP connection a
   node establishes is always following the default behavior.  See
   Section 10.10 for more details.

   The result of an "L2 interface".  Alice
   and Bob will build the candidate ACP connections to each other on every "L2
   interface" that they both connect to.  An neighbor selection process is a list
   of adjacent or configured autonomic node must not
   assume that neighbors with to which an ACP channel
   should be established.  The next step begins that channel
   establishment.

6.5.  Channel Selection

   To avoid attacks, initial discovery of candidate ACP peers cannot
   include any non-protected negotiation.  To avoid re-inventing and
   validating security association mechanisms, the same L2 or link-local IPv6 addresses
   on different L2 interfaces are next step after
   discovering the same node.  This address of a candidate neighbor can only be
   determined after examining the certificate after to try
   first to establish a successful security association attempt.

6.6.  Candidate ACP Neighbor verification

   Independent of with that neighbor using a
   well-known security association method.

   At this time in the lifecycle of ACP nodes, it is unclear whether it
   is feasible to even decide on a single MTI (mandatory to implement)
   security association protocol chosen, candidate across all ACP neighbors nodes.

   From the use-cases it seems clear that not all type of ACP nodes can
   or need to be authenticated based connect directly to each other or are able to support or
   prefer all possible mechanisms.  For example, code space limited IoT
   devices may only support DTLS ("datagram Transport Layer Security
   version 1.2", see [RFC6347]) because that code exists already on their domain
   certificate.  This implies them
   for end-to-end security, but low-end in-ceiling L2 switches may only
   want to support Media Access Control Security (MacSec, see 802.1AE
   ([MACSEC]) because that any is also supported in their chips.  Only a
   flexible gateway device may need to support both of these mechanisms
   and potentially more.

   To support extensible secure channel protocol MUST
   support certificate based authentication that can support selection without a
   single common MTI protocol, ACP nodes must try all the ACP
   domain membership check as defined in Section 6.1.2.  If secure
   channel protocols it fails,
   the connection attempt is aborted supports and an error logged (with
   throttling).

6.7.  Security Association protocols

   The following sections define the security association protocols that
   we consider to be important and are feasible to specify in this document:

6.7.1. because the
   candidate ACP neighbor also announced them via IKEv2

   An ACP node announces its ability to support IKEv2 as AN_ACP GRASP
   parameters (these are called the "feasible" ACP secure channel protocol in GRASP as "IKEv2".

6.7.1.1.  Native IPsec
   protocols).

   To run ACP ensure that the selection of the secure channel protocols always
   succeeds in a predictable fashion without blocking, the following
   rules apply:

   o  An ACP node may choose to attempt initiate the different feasible
      ACP secure channel protocols it supports according to its local
      policies sequentially or in parallel, but it MUST support acting
      as a responder to all of them in parallel.

   o  Once the first secure channel protocol succeeds, the two peers
      know each other's certificates because they must be used by all
      secure channel protocols for mutual authentication.  The node with
      the lower Node-ID in the ACP address becomes Bob, the one with the
      higher Node-ID in the certificate Alice.

   o  Bob becomes passive, he does not attempt to further initiate ACP
      secure channel protocols with Alice and does not consider it to be
      an error when Alice closes secure channels.  Alice becomes the
      active party, continues to attempt setting up secure channel
      protocols with Bob until she arrives at the best one from her view
      that also works with Bob.

   For example, originally Bob could have been the initiator of one ACP
   secure channel protocol that Bob prefers and the security association
   succeeded.  The roles of Bob and Alice are then assigned.  At this
   stage, the protocol may not even have completed negotiating a common
   security profile.  The protocol could for example be IPsec via IKEv2
   ("IP security", see [RFC4301] and "Internet Key Exchange protocol
   version 2", see [RFC7296].  It is now up to Alice to decide how to
   proceed.  Even if the IPsec connection from Bob succeeded, Alice
   might prefer another secure protocol over IPsec (e.g., FOOBAR), and
   try to set that up with Bob.  If that preference of Alice succeeds,
   she would close the IPsec connection.  If no better protocol attempt
   succeeds, she would keep the IPsec connection.

   All this negotiation is in the context of an "L2 interface".  Alice
   and Bob will build ACP connections to each other on every "L2
   interface" that they both connect to.  An autonomic node must not
   assume that neighbors with the same L2 or link-local IPv6 addresses
   on different L2 interfaces are the same node.  This can only be
   determined after examining the certificate after a successful
   security association attempt.

6.6.  Candidate ACP Neighbor verification

   Independent of the security association protocol chosen, candidate
   ACP neighbors need to be authenticated based on their domain
   certificate.  This implies that any secure channel protocol MUST
   support certificate based authentication that can support the ACP
   domain membership check as defined in Section 6.1.2.  If it fails,
   the connection attempt is aborted and an error logged.  Attempts to
   reconnect MUST be throttled.  The RECOMMENDED default is exponential
   backoff with a a minimum delay of 10 seconds and a maximum delay of
   640 seconds.

6.7.  Security Association protocols

   The following sections define the security association protocols that
   we consider to be important and feasible to specify in this document:

6.7.1.  ACP via IKEv2

   An ACP node announces its ability to support IKEv2 as the ACP secure
   channel protocol in GRASP as "IKEv2".

6.7.1.1.  Native IPsec

   To run ACP via IPsec natively, no further IANA assignments/
   definitions are required.  An ACP node that is supporting native
   IPsec MUST use IPsec security setup via IKEv2, tunnel mode, local and
   peer link-
   local link-local IPv6 addresses used for encapsulation.  It MUST then
   support ESP with AES256 for encryption and SHA256 hash and MUST NOT
   permit weaker crypto options.

   In terms of IKEv2, this means the initiator will offer to support
   IPsec tunnel mode with next protocol equal 41 (IPv6).

   IPsec tunnel mode is required because the ACP will route/forward
   packets received from any other ACP node across the ACP secure
   channels, and not only its own generated ACP packets.  With IPsec
   transport mode, it would only be possible to send packets originated
   by the ACP node itself.

   ESP is used because ACP mandates the use of encryption for ACP secure
   channels.

6.7.1.2.  IPsec with GRE encapsulation

   In network devices it is often more common to implement high
   performance virtual interfaces on top of GRE encapsulation than on
   top of a "native" IPsec association (without any other encapsulation
   than those defined by IPsec).  On those devices it may be beneficial
   to run the ACP secure channel on top of GRE protected by the IPsec
   association.

   To run ACP via GRE/IPsec, no further IANA assignments/definitions are
   required.  The  An ACP node MUST that is supporting ACP via GRE/IPsec MUST then
   support IPsec security setup via IKEv2, IPsec transport mode, local
   and peer link-local IPv6 addresses used for encapsuation, encapsulation, ESP with
   AES256 encryption and SHA256 hash.

   When GRE is used, transport mode is sufficient because the routed ACP
   packets are not "tunneled" by IPsec but rather by GRE: IPsec only has
   to deal with the GRE/IP packet which always uses the local and peer
   link-local IPv6 addresses and is therefore applicable to transport
   mode.

   ESP is used because ACP mandates the use of encryption for ACP secure
   channels.

   In terms of IKEv2 negotiation, this means the initiator must offer to
   support IPsec transport mode with next protocol equal to GRE (47)
   followed by the offer for native IPsec as described above (because
   that option is mandatory to support).

   If IKEv2 initiator and responder support GRE, it will be selected.
   The version of GRE to be used must the according to [RFC7676].

6.7.2.  ACP via dTLS DTLS

   We define the use of ACP via dTLS DTLS in the assumption that it is likely
   the first transport encryption code basis supported in some classes
   of constrained devices.

   To run ACP via UDP and dTLS DTLS v1.2 [RFC6347] a locally assigned UDP
   port is used that is announced as a parameter in the GRASP AN_ACP
   objective to candidate neighbors.  All ACP nodes supporting dTLS DTLS as a
   secure channel protocol MUST support AES256 encryption and MUST NOT
   permit weaker crypto options.

   There is no additional session setup or other security association
   besides this simple dTLS DTLS setup.  As soon as the dTLS DTLS session is
   functional, the ACP peers will exchange ACP IPv6 packets as the
   payload of the dTLS DTLS transport connection.  Any dTLS DTLS defined security
   association mechanisms such as re-keying are used as they would be
   for any transport application relying solely on dTLS. DTLS.

6.7.3.  ACP Secure Channel Requirements

   A baseline ACP node MUST support IPsec natively and MAY support IPsec
   via GRE.  A constrained ACP node that can not support IPsec MUST
   support dTLS. DTLS.  ACP nodes connecting constrained areas with baseline
   areas MUST therefore support IPsec and dTLS. DTLS.

   ACP nodes need to specify in documentation the set of secure ACP
   mechanisms they support.

   An ACP secure channel MUST immediately be terminated when the
   lifetime of any certificate in the chain used to authenticate the
   neighbor expires or becomes revoked.  Note that this is not standard
   behavior in secure channel protocols such as IPsec because the
   certificate authentication only influences the setup of the secure
   channel in these protocols.

6.8.  GRASP in the ACP

6.8.1.  GRASP as a core service of the ACP

   The ACP MUST run an instance of GRASP inside of it.  It is a key part
   of the ACP services.  They  The function in GRASP that makes it fundamental
   as a service of the ACP is the ability for to provide ACP wide service
   discovery (called (using objectives in GRASP).  In most other solution
   designs such distributed discovery does not exist at all or was added
   as an afterthought and relied upon inconsistently.

   ACP provides IP unicast routing via the RPL routing protocol
   (described below). (see
   Section 6.11).

   The ACP does not use IP multicast routing nor does it provide generic
   IP multicast services (the handling of GRASP link-local multicast
   messages is explained in the following section). Section 6.8.2).  Instead, the ACP provides
   service discovery via the objective discovery/announcement and
   negotiation mechanisms of the ACP GRASP instance (services are a form
   of objectives).  These mechanisms use hop-by-hop reliable flooding of
   GRASP messages for both service discovery (GRASP M_DISCOVERY
   messages) and service announcement (GRASP M_FLOOD messages).

   IP multicast is not used by the ACP because the ANI (Autonomic
   Networking Infrastructure) itself does not require IP multicast but
   only service announcement/discovery.  Using IP multicast for that
   would have made it necessary to develop a zero-touch autoconfiguring
   solution

   See Section 10.8 for ASM (Any Source Multicast - original form of IP
   multicast defined in [RFC1112]), which would be quite complex and
   difficult to justify.  One aspect of complexity that has never been
   attempted to be solved in IETF documents is the automatic-selection
   of routers that should be PIM-SM rendezvous points (RPs) (see
   [RFC7761]).  The other aspects of complexity are the implementation
   of MLD ([RFC4604]), PIM-SM and Anycast-RP (see [RFC4610]).  If those
   implementations already exist in a product, then they would be very
   likely tied to accelerated forwarding which consumes hardware
   resources, and that in return is difficult to justify as a cost more discussion about this design choice of
   performing only service discovery.

   Future ASA may need high performance in-network data replication.
   That is the case when the use of IP multicast is justified.  These
   ASA can then use service discovery from
   ACP GRASP, and then they do
   not need ASM but only SSM (Source Specific Multicast, see [RFC4607]) considerations for the IP multicast replication.  SSM itself can simply be enabled
   in the data-plane (or even in an update to the ACP) without any other
   configuration than just enabling it on all nodes and only requires a
   simpler version of MLD (see [RFC5790]).

   LSP (Link State Protocol) based IGP routing protocols typically have
   a mechanism to flood information, and such a mechanism could be used
   to flood GRASP objectives by defining them to be information of that
   IGP.  This would be a possible optimization in future variations of
   the ACP that do use an LSP routing protocol.  Note though that such a
   mechanism would not work easily for GRASP M_DISCOVERY messages which
   are constrained flooded up to a node where a responder is found.  We
   do expect that many future services in ASA will have only few
   consuming ASA, and for those cases, M_DISCOVERY is the more efficient
   method than flooding across the whole domain.

   Because the ACP uses RPL, one desirable future extension is to use
   RPLs existing notion of loop-free distribution trees (DODAG) to make
   GRASPs flooding more efficient both for M_FLOOD and M_DISCOVERY) See
   Section 6.12.5 how this will be specifically beneficial when using
   NBMA interfaces.  This is not currently specified in this document
   because it is not quite clear yet what exactly the implications are
   to make GRASP flooding depend on RPL DODAG convergence and how
   difficult it would be to let GRASP flooding access the DODAG
   information. variations.

6.8.2.  ACP as the Security and Transport substrate for GRASP

   In the terminology of GRASP ([I-D.ietf-anima-grasp]), the ACP is the
   security and transport substrate for the GRASP instance run inside
   the ACP ("ACP GRASP").

   This means that the ACP is responsible to ensure for ensuring that this
   instance of GRASP is only sending messages across the ACP GRASP
   virtual interfaces.  Whenever the ACP adds or deletes such an
   interface because of new ACP secure channels or loss thereof, the ACP
   needs to indicate this to the ACP instance of GRASP.  The ACP exists
   also in the absence of any active ACP neighbors.  It is created when
   the node has a domain certificate, and continues to exist even if all
   of its neighbors cease operation.

   In this case ASAs using GRASP running on the same node would still
   need to be able to discover each other's objectives.  When the ACP
   does not exist, ASAs leveraging the ACP instance of GRASP via APIs
   MUST still be able to operate, and MUST be able to understand that
   there is no ACP and that therefore the ACP instance of GRASP can not
   operate.

   The way ACP acts as the security and transport substrate for GRASP is
   visualized in the following picture:

   [RFC Editor: please try to put the following picture on a single page
   and remove this note.  We cannot figure out how to do this with XML.
   The picture does fit on a single page.]

            ACP:
       ...............................................................
       .                                                             .
       .         /-GRASP-flooding-\         ACP GRASP instance       .
       .        /                  \                                 .
       .    GRASP      GRASP      GRASP                              .
       .  link-local   unicast  link-local                           .
       .   multicast  messages   multicast                           .
       .   messages      |       messages                            .
       .      |          |          |                                .
       ...............................................................
       .      v          v          v    ACP security and transport  .
       .      |          |          |    substrate for GRASP         .
       .      |          |          |                                .
       .      |       ACP GRASP     |       - ACP GRASP              .
       .      |       loopback       Loopback      |         loopback         Loopback interface     .
       .      |       interface     |       - AN-cert ACP-cert auth          .
       .      |         TLS         |                                .
       .   ACP GRASP     |       ACP GRASP  - ACP GRASP virtual      .

       .   subnet1       |       subnet2      virtual interfaces     .
       .     TCP         |         TCP                               .
       .      |          |          |                                .
       ...............................................................
       .      |          |          |   ^^^ Users of ACP (GRASP/ASA) .
       .      |          |          |   ACP interfaces/addressing    .
       .      |          |          |                                .
       .      |          |          |                                .
       .      | ACP-loopback ACP-Loopback Interf.|      <- ACP loopback Loopback interface .
       .      |      ACP-address    |       - address (global ULA)   .
       .    subnet1      |        subnet2  <- ACP virtual interfaces .
       .  link-local     |      link-local  - link-local addresses   .
       ...............................................................
       .      |          |          |   ACP routing and forwarding   .
       .      |     RPL-routing     |                                .
       .      |   /IP-Forwarding\   |                                .
       .      |  /               \  |                                .
       .  ACP IPv6 packets   ACP IPv6 packets                        .
       .      |/                   \|                                .
       .    IPsec/dTLS        IPsec/dTLS    IPsec/DTLS        IPsec/DTLS  - AN-cert ACP-cert auth            .
       ...............................................................
                |                   |   data-plane   Data-Plane
                |                   |
                |                   |     - ACP secure channel
            link-local        link-local  - encap encapsulation addresses
              subnet1            subnet2  - data-plane Data-Plane interfaces
                |                   |
             ACP-Nbr1            ACP-Nbr2

        Figure 2

   GRASP unicast messages 7: ACP as security and transport substrate for GRASP

   GRASP unicast messages inside the ACP always use the ACP address.
   Link-local ACP addresses must not be used inside objectives.  GRASP
   unicast messages inside the ACP are transported via TLS 1.2
   ([RFC5246]) connections with AES256 encryption and SHA256.  Mutual
   authentication uses the ACP domain membership check defined in
   (Section 6.1.2).

   GRASP link-local multicast messages are targeted for a specific ACP
   virtual interface (as defined Section 6.12.5) but are sent by the ACP
   into an ACP GRASP virtual interface that is constructed from the TCP
   connection(s) to the IPv6 link-local neighbor address(es) on the
   underlying ACP virtual interface.  If the ACP GRASP virtual interface
   has two or more neighbors, the GRASP link-local multicast messages
   are replicated to all neighbor TCP connections.

   TLS and TLS connections for GRASP in the ACP use the IANA assigned
   TCP port for GRASP (7107).  Effectively the transport stack is
   expected to be TLS for connections from/to the ACP address (e.g.: (e.g.,
   global scope address(es)) and TCP for connections from/to link-local
   addresses on the ACP virtual interfaces.  The latter ones are only
   used for flooding of GRASP messages.

6.8.2.1.  Discussion

   TCP encapsulation for GRASP M_DISCOVERY and M_FLOOD link local
   messages is used because these messages are flooded across
   potentially many hops to all ACP nodes and a single link with even
   temporary packet loss issues (e.g.: (e.g., WiFi/Powerline link) can reduce
   the probability for loss free transmission so much that applications
   would want to increase the frequency with which they send these
   messages.  This  Such shorter periodic retransmission of datagrams would
   result in more traffic flooding and processing overhead in the ACP than the
   hop-by-hop reliable retransmission as provided for mechanism by TCP and duplicate
   elimination by TCP. GRASP.

   TLS is mandated for GRASP non-link-local unicast because the ACP
   secure channel mandatory authentication and encryption protects only
   against attacks from the outside but not against attacks from the
   inside: Compromised ACP members that have (not yet) been detected and
   removed (e.g.: (e.g., via domain certificate revocation / expiry).

   If GRASP peer connections would just use TCP, compromised ACP members
   could simply eavesdrop passively on GRASP peer connections for whom
   they are on-path ("Man In The Middle" - MITM).  Or intercept and
   modify them.  With TLS, it is not possible to completely eliminate
   problems with compromised ACP members, but attacks are a lot more
   complex:

   Eavesdropping/spoofing by a compromised ACP node is still possible
   because in the model of the ACP and GRASP, the provider and consumer
   of an objective have initially no unique information (such as an
   identity) about the other side which would allow them to distinguish
   a benevolent from a compromised peer.  The compromised ACP node would
   simply announce the objective as well, potentially filter the
   original objective in GRASP when it is a MITM and act as an
   application level proxy.  This of course requires that the
   compromised ACP node understand the semantic semantics of the GRASP
   negotiation to an extend extent that allows it to proxy it without being
   detected, but in an AN ACP environment this is quite likely public
   knowledge or evens even standardized.

   The GRASP TLS connections are run like any other ACP traffic through
   the ACP secure channels.  This leads to double authentication/
   encryption.  Future work optimizations could avoid this but it is
   unclear how beneficial/feasible this is:

   o  The security considerations for GRASP change against attacks from
      non-ACP (e.g.: (e.g., "outside") nodes: TLS is subject to reset attacks
      while secure channel protocols may be not (e.g.: (e.g., IPsec is not).

   o  The secure channel method may leverage hardware acceleration and
      there may be little or no gain in eliminating it.

   o  The GRASP TLS connections need to implement any additional
      security options that are required for secure channels.  For
      example the closing of connections when the peers certificate has
      expired.

6.9.  Context Separation

   The ACP is in a separate context from the normal data-plane Data-Plane of the
   node.  This context includes the ACP channels channels' IPv6 forwarding and
   routing as well as any required higher layer ACP functions.

   In classical network systems, system, a dedicated so called "Virtual Virtual routing
   and forwarding instance" instance (VRF) is one logical implementation option
   for the ACP.  If possible by the systems software architecture,
   separation options that minimize shared components are preferred,
   such as a logical container or virtual machine instance.  The context
   for the ACP needs to be established automatically during bootstrap of
   a node.  As much as possible it should be protected from being
   modified unintentionally by ("data-plane") ("Data-Plane") configuration.

   Context separation improves security, because the ACP is not
   reachable from the global routing table.  Also, configuration errors
   from the data-plane Data-Plane setup do not affect the ACP.

6.10.  Addressing inside the ACP

   The channels explained above typically only establish communication
   between two adjacent nodes.  In order for communication to happen
   across multiple hops, the autonomic control plane requires ACP
   network wide valid addresses and routing.  Each ACP node must create
   a loopback Loopback interface with an ACP network wide unique address inside
   the ACP context (as explained in in Section 6.9).  This address may
   be used also in other virtual contexts.

   With the algorithm introduced here, all ACP nodes in the same routing
   subdomain have the same /48 ULA global ID prefix.  Conversely, ULA global IDs
   from different domains are unlikely to clash, such that two ACP
   networks can be merged, as long as the policy allows that merge.  See
   also Section 9.1 for a discussion on merging domains.

   Links inside the ACP only use link-local IPv6 addressing, such that
   each nodes ACP only requires one routable virtual address.

6.10.1.  Fundamental Concepts of Autonomic Addressing

   o  Usage: Autonomic addresses are exclusively used for self-
      management functions inside a trusted domain.  They are not used
      for user traffic.  Communications with entities outside the
      trusted domain use another address space, for example normally
      managed routable address space (called "data-plane" "Data-Plane" in this
      document).

   o  Separation: Autonomic address space is used separately from user
      address space and other address realms.  This supports the
      robustness requirement.

   o  Loopback-only: Only ACP loopback Loopback interfaces (and potentially those
      configured for "ACP connect", see Section 8.1) carry routable
      address(es); all other interfaces (called ACP virtual interfaces)
      only use IPv6 link local addresses.  The usage of IPv6 link local
      addressing is discussed in [RFC7404].

   o  Use-ULA: For loopback Loopback interfaces of ACP nodes, we use Unique Local
      Addresses (ULA), specifically ULA-Random, as defined in [[RFC4193] [RFC4193] with L=1]. L=1 (as defined in
      section 3.1 of [RFC4193]).  Note that the random hash for ACP
      Loopback addresses uses the definition in Section 6.10.2 and not
      the one of [RFC4193] section 3.2.2.

   o  No external connectivity: They do not provide access to the
      Internet.  If a node requires further reaching connectivity, it
      should use another, traditionally managed address scheme in
      parallel.

   o  Addresses in the ACP are permanent, and do not support temporary
      addresses as defined in [RFC4941].

   o  Addresses in the ACP are not considered sensitive on privacy
      grounds because ACP nodes are not expected to be end-user devices.
      Therefore, ACP addresses do not need to be pseudo-random as
      discussed in [RFC7721].  Because they are not propagated to
      untrusted (non ACP) nodes and stay within a domain (of trust), we
      also consider them not to be subject to scanning attacks.

   The ACP is based exclusively on IPv6 addressing, for a variety of
   reasons:

   o  Simplicity, reliability and scale: If other network layer
      protocols were supported, each would have to have its own set of
      security associations, routing table and process, etc.

   o  Autonomic functions do not require IPv4: Autonomic functions and
      autonomic service agents are new concepts.  They can be
      exclusively built on IPv6 from day one.  There is no need for
      backward compatibility.

   o  OAM protocols no do not require IPv4: The ACP may carry OAM
      protocols.  All relevant protocols (SNMP, TFTP, SSH, SCP, Radius,
      Diameter, ...) are available in IPv6.  See also [RFC8368] for how
      ACP could be made to interoperate with IPv4 only OAM.

6.10.2.  The ACP Addressing Base Scheme

   The Base ULA addressing scheme for ACP nodes has the following
   format:

     8      40                     2                     78
   +--+-------------------------+------+------------------------------+
   |fd| hash(routing-subdomain) | Type |     (sub-scheme)             |
   +--+-------------------------+------+------------------------------+

                   Figure 3: 8: ACP Addressing Base Scheme

   The first 48 bits follow the ULA scheme, as defined in [RFC4193], to
   which a type field is added:

   o  "fd" identifies a locally defined ULA address.

   o  The 40 bits ULA "global ID" (term from [RFC4193]) for ACP
      addresses carried in the domain information field of domain
      certificates are the first 40 bits of the SHA256 hash of the
      routing subdomain from the same domain information field.  In the
      example of Section 6.1.1, the routing subdomain is
      "area51.research.acp.example.com" and the 40 bits ULA "global ID"
      89b714f3db.

   o  To allow for extensibility, the fact that the ULA "global ID" is a
      hash of the routing subdomain SHOULD NOT be assumed by any ACP
      node during normal operations.  The hash function is only executed
      during the creation of the certificate.  If BRSKI is used then the
      BRSKI registrar will create the domain information field in
      response to the CSR EST Certificate Signing Request (CSR) Attribute
      Request message by the pledge.

   o  Type: This field allows different address sub-schemes.  This
      addresses the "upgradability" requirement.  Assignment of types
      for this field will be maintained by IANA.

   The sub-scheme may imply a range or set of addresses assigned to the
   node, this is called the ACP address range/set and explained in each
   sub-scheme.

   Please refer to Section 6.10.7 and Section 10.4 for further
   explanations why the following Sub-Addressing schemes are used and
   why multiple are necessary.

6.10.3.  ACP Zone Addressing Sub-Scheme

   The sub-scheme defined here is defined by the Type value 00b (zero)
   in the base scheme. scheme and 0 in the Z bit.

                    64                             64
   +-----------------+---------+---++-----------------------------+---+
   +-----------------+---+---------++-----------------------------+---+
   |  (base scheme)  | Zone-ID | Z | Zone-ID ||           Node-ID               |
   |                 |   |         || Registrar-ID |   Node-Number| V |
   +-----------------+---------+---++--------------+--------------+---+
   +-----------------+---+---------++--------------+--------------+---+
            50              13         1     13            48           15          1

                 Figure 4: 9: ACP Zone Addressing Sub-Scheme

   The fields are defined as follows:

   o  Zone-ID: If set to all zero bits: The Node-ID bits are used as an
      identifier (as opposed to a locator).  This results in a non-
      hierarchical, flat addressing scheme.  Any other value indicates a
      zone.  See Section 6.10.3.1 on how this field is used in detail.

   o  Z: MUST be 0.

   o  Node-ID: A unique value for each node.

   The 64 bit Node-ID is derived and composed as follows:

   o  Registrar-ID (48 bit): A number unique inside the domain that
      identifies the ACP registrar which assigned the Node-ID to the
      node.  A MAC address of the ACP registrar can be used for this
      purpose.

   o  Node-Number: A number which is unique for a given ACP registrar,
      to identify the node.  This can be a sequentially assigned number.

   o  V (1 bit): Virtualization bit: 0: Indicates the ACP itself ("ACP
      node base system); 1: Indicates the optional "host" context on the
      ACP node (see below).

   In the ACP Zone Addressing Sub-Scheme, the ACP address in the
   certificate has Zone-ID and V fields as all zero bits.  The ACP
   address set includes addresses with any Zone-ID value and any V
   value.

   The "Node-ID" itself is unique in a domain (i.e., the Zone-ID is not
   required for uniqueness).  Therefore, a node can be addressed either
   as part of a flat hierarchy (Zone-ID = 0), or with an aggregation
   scheme (any other Zone-ID).  An address with Zone-ID = 0 is an
   identifier, with a Zone-ID !=0 it is a locator.  See Section 6.10.3.1
   for more details.

   The Virtual bit in this sub-scheme allows to easily add the easy addition of the
   ACP as a component to existing systems without causing problems in
   the port number space between the services in the ACP and the
   existing system.  V:0 is the ACP router (autonomic node base system),
   V:1 is the host with pre-existing transport endpoints on it that
   could collide with the transport endpoints used by the ACP router.
   The ACP host could for example have a p2p virtual interface with the
   V:0 address as its router into the ACP.  Depending on the SW software
   design of ASA (outside ASAs, which is outside the scope of this specification), specification,
   they may use the V:0 or V:1 address.

   The location of the V bit(s) at the end of the address allows to
   announce the
   announcement of a single prefix for each ACP node.  For example, in a
   network with 20,000 ACP nodes, this avoid 20,000 additional routes in
   the routing table.

6.10.3.1.  Usage of the Zone-ID Field

   The Zone-ID allows for the introduction of structure in the
   addressing scheme.

   Zone-ID = 0 is the default addressing scheme in an ACP domain.  Every
   ACP node with a Zone Addressing Sub-Scheme address MUST respond to
   its ACP address with Zone-ID = 0.  Used on its own this leads to a
   non-hierarchical address scheme, which is suitable for networks up to
   a certain size.  Zone-ID = 0 addresses act as identifiers for the
   nodes, and aggregation of these address in the ACP routing table is
   not possible.

   If aggregation is required, the 13 bit Zone-ID value allows for up to
   8191 zones.  The allocation of Zone-ID's may either happen
   automatically through a to-be-defined algorithm; or it could be
   configured and maintained explicitly.

   If a node learns through a future autonomic method or through
   configuration that it is part of a zone, it MUST also respond to its
   ACP address with that Zone-ID.  In this case the ACP loopback Loopback is
   configured with two ACP addresses: One for Zone-ID = 0 and one for
   the assigned Zone-ID.  This method allows for a smooth transition
   between a flat addressing scheme and an hierarchical one.

   A node knowing it is in a zone MUST also use that Zone-ID != 0
   address in GRASP locator fields.  This eliminates the use of the
   identifier address (Zone-ID = 0) in forwarding and the need for
   network wide reachability of those non-aggregateable non-aggregatable identifier
   addresses.  Zone-ID != 0 addresses are assumed to be aggregateable aggregatable in
   routing/forwarding based on how they are allocated in the ACP
   topology (subject to future work).

   Note: Theoretically, the 13 bits for the Zone-ID would allow also for
   two levels of zones, introducing a sub-hierarchy.  We do not think
   this is required at this point, but a new type could be used in the
   future to support such a scheme.

   Note: The Zone-ID is one method to introduce structure or hierarchy
   into the ACP.  Another way is the use of the routing subdomain field
   in the ACP that leads to different /40 ULA prefixes multiple /48 Global IDs within an ACP
   domain.  This gives future work two options to consider.

   Note: Zones and Zone-ID as defined here are not related to [RFC4007]
   zones or zone_id.  ACP zone addresses are not scoped (reachable only
   from within an RFC4007 zone) but reachable across the whole ACP.  An
   RFC4007 zone_id is a zone index that has only local significance on a
   node, whereas an ACP Zone-ID is an identifier for an ACP zone that is
   unique across that ACP.

6.10.4.  ACP Manual Addressing Sub-Scheme

   The sub-scheme defined here is defined by the Type value 00b (zero)
   in the base scheme. scheme and 1 in the Z bit.

                   64                             64
   +---------------------+---------+---++-----------------------------+
   +---------------------+---+----------++-----------------------------+
   |    (base scheme)    |Subnet-ID|    | Z || | Subnet-ID||     Interface Identifier    |
   +---------------------+---------+---++-----------------------------+
   +---------------------+---+----------++-----------------------------+
            50             13             1    13

                Figure 5: 10: ACP Manual Addressing Sub-Scheme

   The fields are defined as follows:

   o  Subnet-ID: Configured subnet identifier.

   o  Z: MUST be 1.

   o  Interface Identifier.

   This sub-scheme is meant for "manual" allocation to subnets where the
   other addressing schemes cannot be used.  The primary use case is for
   assignment to ACP connect subnets (see Section 8.1.1).

   "Manual" means that allocations of the Subnet-ID need to be done
   today with pre-existing, non-autonomic mechanisms.  Every subnet that
   uses this addressing sub-scheme needs to use a unique Subnet-ID
   (unless some anycast setup is done).  Future work may define
   mechanisms for auto-coordination between ACP nodes and auto-
   allocation of Subnet-IDs between them.

   The Z bit field is following the Subnet-ID field so that future work
   could allocate/coordinate both Zone-ID was added to distinguish Zone addressing and Subnet-ID consistently manual
   addressing sub-schemes without requiring one more bit in the base
   scheme and
   use an integrated aggregatable routing approach across them.  Z=0
   (Zone-ID sub-scheme) would then be used for network wide unique,
   registrar assigned (and certificate protected) Node-IDs primarily for
   ACP nodes while Z=1 would be used for node-level assigned Interface
   Identifiers primarily therefore allowing for non-ACP-nodes (on logical subnets where the
   ACP node is a router). Vlong scheme (described below)
   to have one more bit available.

   Manual addressing sub-scheme addresses SHOULD only be used in domain
   certificates assigned to nodes that cannot fully participate in the
   automatic establishment of ACP secure channels or ACP routing.  The
   intended use are nodes connecting to the ACP via an ACP edge node and
   ACP connect interfaces (see Section 8.1) - such as legacy NOC
   equipment.  They would not use their domain certificate for ACP
   secure channel creation and therefore do not need to participate in
   ACP routing either.  They would use the certificate for
   authentication of any transport services.  The value of the Interface
   Identifier is left for future definitions.

6.10.5.  ACP Vlong Addressing Sub-Scheme

   The sub-scheme defined here is defined by the Type value 01b (one) in
   the base scheme.

             50                              78
   +---------------------++-----------------------------+----------+
   |    (base scheme)    ||           Node-ID                      |
   |                     || Registrar-ID |   Node-Number|        V |
   +---------------------++--------------+--------------+----------+
             50                46             24/16          8/16

                Figure 6: 11: ACP Vlong Addressing Sub-Scheme

   This addressing scheme foregoes the Zone-ID field to allow for
   larger, flatter routed networks (e.g.: (e.g., as in IoT) with 8421376 Node-
   Numbers (2^23+2^15).  It also allows for up to 2^16 - 65536 (i.e. 65536)
   different virtualized addresses within a node, which could be used to
   address individual software components in an ACP node.

   The fields are the same as in the Zone-ID sub-scheme with the
   following refinements:

   o  V: Virtualization bit: Values 0 and 1 are assigned in the same way
      as in the Zone-ID sub-scheme,
      further values use via definition in future work. sub-scheme.

   o  Registrar-ID: To maximize Node-Number and V, the Registrar-ID is
      reduced to 46 bits.  This still allows to permits the use of the MAC address
      of a an ACP registrar by removing the V and U bits from the 48 bits
      of a MAC address (those two bits are never unique, so they cannot
      be used to distinguish MAC addresses).

   o  If the first bit of the "Node-Number" is "1", then the Node-Number
      is 16 bit long and the V field is 16 bit long.  Otherwise the
      Node-Number is 24 bit long and the V field is 8 bit long.

   "0" bit Node-Numbers are intended to be used for "general purpose"
   ACP nodes that would potentially have a limited number (< 256) of
   clients (ASA/Autonomic Functions or legacy services) of the ACP that
   require separate V(irtual) addresses.  "1" bit Node-Numbers are
   intended for ACP nodes that are ACP edge nodes (see Section 8.1.1) or
   that have a large number of clients requiring separate V(irtual)
   addresses.  For example large SDN controllers with container modular
   software architecture (see Section 8.1.2).

   In the Vlong addressing sub-scheme, the ACP address in the
   certificate has all V field bits as zero.  The ACP address set for
   the node includes any V value.

6.10.6.  Other ACP Addressing Sub-Schemes

   Before further addressing sub-schemes are defined, experience with
   the schemes defined here should be collected.  The schemes defined in
   this document have been devised to allow hopefully sufficiently
   flexible setup of ACPs for a variety of situation.  These reasons
   also lead to the fairly liberal use of address space: The Zone
   Addressing Sub-Scheme is intended to enable optimized routing in
   large networks by reserving bits for Zone-ID's.  The Vlong addressing
   sub-scheme enables the allocation of 8/16 bit of addresses inside
   individual ACP nodes.  Both address spaces allow distributed,
   uncoordinated allocation of node addresses by reserving bits for the
   Registrar-ID
   registrar-ID field in the address.

   IANA is asked need to assign a new "type" for each new addressing
   sub-scheme.  With the current allocations, only 2 more schemes are
   possible, so the last addressing scheme should consider to be
   extensible in itself (e.g.: making
   provisions provision for further extensions (e.g., by reserving bits
   from it for further
   extensions.

6.11.  Routing in the extensions).

6.10.7.  ACP Registrars

   The ACP

   Once ULA address are set up all autonomic entities should run a
   routing protocol within the autonomic control plane context.  This
   routing protocol distributes the ULA created in prefix is assigned to the previous section
   for reachability.  The use ACP node during enrollment/
   provisioning of the autonomic control plane specific
   context eliminates ACP domain certificate to the probable clash with ACP node.  It is
   intended to persist unchanged through the global routing table
   and also secures lifetime of the ACP from interference from the configuration
   mismatch or incorrect routing updates.

   The establishment node.

   Because of the routing plane ACP addressing sub-schemes explained above, ACP nodes
   for a single ACP domain can be enrolled by multiple distributed and its parameters
   uncoordinated entities called ACP registrars.  These ACP registrars
   are
   automatic responsible to enroll ACP domain certificates and associated
   trust anchor(s) to candidate ACP nodes and strictly within the confines of the autonomic control
   plane.  Therefore, no explicit configuration is required.

   All routing updates are automatically secured also responsible that
   an ACP domain information field is included in transit as the
   channels ACP domain
   certificate.

6.10.7.1.  Use of BRSKI or other Mechanism/Protocols

   Any protocols or mechanisms may be used as ACP registrars, as long as
   the autonomic control plane are by default secured, resulting ACP certificate and
   this routing runs only inside the ACP.

   The routing protocol inside trust anchors allow to perform the
   ACP is RPL ([RFC6550]).  See domain membership described in Section 10.5 6.1.2 with other ACP
   domain members, and meet the ACP addressing requirements for more details on its ACP
   domain information field as described further below in this section.

   An ACP registrar could be a person deciding whether to enroll a
   candidate ACP node and then orchestrating the choice enrollment of RPL.

   RPL adjacencies are set up across all the ACP channels in
   certificate and associated trust anchor, using command line or web
   based commands on the same candidate ACP node and trust anchor to generate
   and sign the ACP domain
   including all its routing subdomains.  See Section 10.7 for more
   details.

6.11.1.  RPL Profile certificate and configure certificate and
   trust anchors onto the node.

   The following only currently defined protocol for ACP registrars is a description of BRSKI
   ([I-D.ietf-anima-bootstrapping-keyinfra]).  When BRSKI is used, the RPL profile that
   ACP nodes need
   to support by default. are called ANI nodes, and the ACP registrars are called
   BRSKI or ANI registrars.  The format BRSKI specification does not define the
   handling of this section is derived from
   draft-ietf-roll-applicability-template.

6.11.1.1.  Summary

   In summary, the profile chosen for RPL is one that expects a fairly
   reliable network reasonable fast links so ACP domain information field because the rules do not
   depend on BRSKI but apply equally to any protocols/mechanisms an ACP
   registrar may use.

6.10.7.2.  Unique Address/Prefix allocation

   ACP registrars MUST NOT allocate ACP address prefixes to ACP nodes
   via the ACP domain information field that RPL convergence will
   be triggered immediately upon recognition of link failure/recovery.

   The key limitation would collide with the ACP
   address prefixes of other ACP nodes in the chosen profile is that it is designed same ACP domain.  This
   includes both prefixes allocated by the same ACP registrar to
   not require any data-plane artifacts (such
   different ACP nodes as [RFC6553]).  While well as prefixes allocated by other ACP
   registrars for the
   senders/receivers same ACP domain.

   For this purpose, an ACP registrar MUST have one or more unique 46
   bit identifiers called Registrar-IDs used to allocate ACP address
   prefixes.  The lower 46 bits of a EUI-48 MAC addresses are globally
   unique 46 bit identifiers, so ACP packets registrars with known unique EUI-48
   MAC addresses can be legacy NOC devices connected
   via "ACP connect" (see Section 8.1.1 use these as Registrar-IDs.  Registrar-IDs do not
   need to be globally unique but only unique across the ACP, their connectivity set of ACP
   registrars for an ACP domain, so other means to assign unique
   Registrar-IDs to ACP registrars can be handled used, such as non-RPL-aware leafs (or "Internet") according to configuration on
   the data-plane architecture explained ACP registrars.

   When the candidate ACP device (called Pledge in
   [I-D.ietf-roll-useofrplinfo].  This non-artifact profile BRSKI) is largely
   driven by the desire to avoid introducing the required Hop-by-Hop
   headers be
   enrolled into the an ACP VRF control plane.  Many devices will have their
   VRF forwarding code designed into silicon.

   In this profile choice, RPL has no data-plane artifacts.  A simple
   destination prefix based upon domain, the routing table is used.  A
   consequence of supporting only ACP registrar needs to allocate a single instanceID (containing one
   DODAG),
   unique ACP address to the node and ensure that the ACP will only accommodate only certificate
   gets a single class of routing
   table domain information field (Section 6.1.1) with the appropriate
   information - ACP domain-name, ACP-address, and cannot create optimized routing paths so on.  If the ACP
   registrar uses BRSKI, it signals the ACP information field to accomplish latency the
   Pledge via the EST /csraddrs command (see
   [I-D.ietf-anima-bootstrapping-keyinfra], section 5.8.2 - "EST CSR
   Attributes").

   [RFC editor: please update reference to section 5.8.2 accordingly
   with latest BRSKI draft at time of publishing, or energy goals.

   Consider RFC]

6.10.7.3.  Addressing Sub-Scheme Policies

   The ACP registrar selects for the candidate ACP node a network that has multiple NOCs unique address
   prefix from an appropriate ACP addressing sub-scheme, either a zone
   addressing sub-scheme prefix (see Section 6.10.3), or a Vlong
   addressing sub-scheme prefix (see Section 6.10.5).  The assigned ACP
   address prefix encoded in different locations.
   Only one NOC will become the DODAG root.  Other NOCs will have domain information field of the ACP
   domain certificate indicates to
   send traffic through the DODAG (tree) rooted in ACP node its ACP address
   information.  The sub-addressing scheme indicates the primary NOC.
   Depending on topology, this can be an annoyance from a latency point
   of view, but it does not represent a single point prefix length:
   /126 for zone address sub-scheme, /120 or /112 for Vlong address sub-
   scheme.  The first address of failure, the prefix is the ACP address, all
   other addresses in the prefix are for other uses by the ACP node as
   described in the
   DODAG can reconfigure zone and Vlong addressing sub scheme sections.  The
   ACP address prefix itself when it detects data plane forwarding
   failures. is then signaled by the ACP node into the
   ACP routing protocol (see Section 6.11) to establish IPv6
   reachability across the ACP.

   The lack choice of a RPI (the header defined by [RFC6553]), means that addressing sub-scheme and prefix-length in the
   data-plane will have no rank value that can be used Vlong
   address sub-scheme is subject to detect loops.
   As ACP registrar policy.  It could be
   an ACP domain wide policy, or a result, traffic may loop until per ACP node or per ACP node type
   policy.  For example, in BRSKI, the TTL ACP registrar is aware of the packet reaches
   zero.  This the same behavior as that
   IDevID of other IGPs that do not have the data-plane options as RPPL.  There are candidate ACP node, which contains a variety of heuristics serialNnumber that
   is typically indicating the nodes vendor and device type and can be
   used to signal from drive a policy selecting an appropriate addressing sub-scheme
   for the data-plane (class of) node(s).

   ACP registrars SHOULD default to the RPL control
   plane that a new route is needed.

   Additionally, failed allocate ACP tunnels will be detected by IKEv2 Dead Peer
   Detection (which can function as a replacement for an LLN's ETX).  A
   failure zone sub-address scheme
   addresses with Subnet-ID 0.  Allocation and use of an ACP tunnel should signal zone sub-addresses
   with Subnet-ID != 0 is outside the RPL control plane scope of this specification
   because it would need to pick
   a different parent.

   Future Extensions go along with rules for extending ACP
   routing to multiple zones, which is outside the scope of this RPL profile
   specification.

   ACP registrars that can provide optimality use the IDevID of a candidate ACP device
   SHOULD be able to choose the zone vs. Vlong sub-address scheme for
   multiple NOCs.  This requires utilizing data-plane artifact including
   IPinIP encap/decap on
   ACP routers and processing nodes based on the serialNumber of IPv6 RPI headers.
   Alternatively, (Src,Dst) routing table entries could be used.  A
   decision the IDevID, for example by the preferred technology would have to be done when such
   extension is defined.

6.11.1.2.  RPL Instances

   Single RPL instance.  Default RPLInstanceID = 0.

6.11.1.3.  Storing vs. Non-Storing Mode

   RPL Mode of Operations (MOP): mode 3 "Storing Mode of Operations
   PID (Product Identifier) part which identifies the product type, or
   the complete serialNumber.

   In a simple allocation scheme, an ACP registrar remembers
   persistently across reboots for its currently used Registrar-ID and
   for each addressing scheme (zone with
   multicast support".  Implementations should support also other modes.
   Note: Root indicates mode in DIO flow.

6.11.1.4.  DAO Policy

   Proactive, aggressive DAO state maintenance:

   o  Use K-flag in unsolicited DAO indicating change from previous
      information (to require DAO-ACK).

   o  Retry such DAO DAO-RETRIES(3) times Subnet-ID 0, Vlong with DAO- ACK_TIME_OUT(256ms)
      in between.

6.11.1.5.  Path Metric

   Hopcount.

6.11.1.6.  Objective Function

   Objective Function (OF): Use OF0 [RFC6552].  No use of metric
   containers.

   rank_factor: Derived from link speed: <= 100Mbps:
   LOW_SPEED_FACTOR(5), else HIGH_SPEED_FACTOR(1)

6.11.1.7.  DODAG Repair

   Global Repair: we assume stable links /112,
   Vlong with /120), the next Node-Number available for allocation and ranks (metrics), so no need
   increases it after successful enrollment to periodically rebuild DODAG.  DODAG version only incremented under
   catastrophic events (e.g.: administrative action).

   Local Repair: As soon as link breakage is detected, send No-Path DAO
   for all the targets that where reachable only via this link.  As soon
   as link repair is detected, validate if an ACP node.  In this link provides you a
   better parent.  If so, compute your new rank, and send new DIO that
   advertises your new rank.  Then send a DAO with a new path sequence
   about yourself.

   stretch_rank: none provided ("not stretched").

   Data Path Validation: Not used.

   Trickle: Not used.

6.11.1.8.  Multicast

   Not used yet but possible because of
   simple allocation scheme, the selected mode of operations.

6.11.1.9.  Security

   [RFC6550] security ACP registrar would not used, substituted by recycle ACP security.

6.11.1.10.  P2P communications

   Not used.

6.11.1.11.  IPv6
   address configuration

   Every prefixes from no longer used ACP node (RPL node) announces nodes.

6.10.7.4.  Address/Prefix Persistence

   When an IPv6 prefix covering ACP domain certificate is renewed or rekeyed via EST or other
   mechanisms, the
   address(es) used ACP address/prefix in the ACP node.  The prefix length depends on the
   chosen addressing sub-scheme domain information
   field MUST be maintained unless security issues or violations of the ACP
   unique address provisioned into assignment requirements exist or are suspected by the
   certificate of
   ACP registrar.  Even when the renewing/rekeying ACP node, e.g.: /127 registrar is not
   the same as the one that enrolled the prior ACP certificate.  See
   Section 10.3.4 for Zone Addressing Sub-
   Scheme or /112 an example.  ACP address information SHOULD also
   be maintained even after an ACP certificate did expire or /120 for Vlong addressing sub-scheme. failed.
   See Section 6.10 for more details.

   Every 6.1.3.5 and Section 6.1.3.6.

6.10.7.5.  Further Details

   Section 10.3 discusses further non-normative details of ACP node MUST install a black hole (aka null) route for
   whatever
   registrars: What interactions registrars need, what parameters they
   require, certificate renewal and limitations, use of sub-CAs on
   registrars and centralized policy control.

6.11.  Routing in the ACP

   Once ULA address space that it advertises (i.e.: are set up all autonomic entities should run a
   routing protocol within the /96 or
   /127). autonomic control plane context.  This is avoid
   routing loops for addresses that an ACP node
   has not (yet) used.

6.11.1.12.  Administrative parameters

   Administrative Preference ([RFC6552], 3.2.6 - to become root):
   Indicated protocol distributes the ULA created in DODAGPreference field the previous section
   for reachability.  The use of DIO message.

   o  Explicit configured "root": 0b100

   o  Registrar (Default): 0b011

   o  AN-connect (non-registrar): 0b010

   o  Default: 0b001.

6.11.1.13.  RPL Data-Plane artifacts

   RPI (RPL Packet Information [RFC6553]): Not used as there is only a
   single instance, the autonomic control plane specific
   context eliminates the probable clash with the global routing table
   and data path validation is not being used.

   SRH (RPL Source Routing - RFC6552): Not used.  Storing mode is being
   used.

6.11.1.14.  Unknown Destinations

   Because RPL minimizes also secures the size ACP from interference from the configuration
   mismatch or incorrect routing updates.

   The establishment of the routing plane and forwarding table,
   prefixes reachable through its parameters are
   automatic and strictly within the same interface as confines of the RPL root autonomic control
   plane.  Therefore, no explicit configuration is required.

   All routing updates are not
   known on every ACP node.  Therefore traffic to unknown destination
   addresses can only be discovered at automatically secured in transit as the RPL root.  The RPL root
   SHOULD have attach safe mechanisms to operationally discover and log
   such packets.

6.12.  General ACP Considerations

   Since
   channels of the autonomic control plane are by default established between adjacent neighbors,
   the resulting overlay network does hop by hop encryption.  Each node
   decrypts incoming traffic from the ACP, secured, and encrypts outgoing traffic
   to its neighbors in
   this routing runs only inside the ACP.  Routing

   The routing protocol inside the ACP is discussed in RPL ([RFC6550]).  See
   Section 6.11.

6.12.1.  Performance

   There 10.7 for more details on the choice of RPL.

   RPL adjacencies are no performance requirements against set up across all ACP implementations
   defined channels in this document because the performance requirements depend
   on the intended use case.  It same domain
   including all its routing subdomains.  See Section 10.10 for more
   details.

6.11.1.  RPL Profile

   The following is expected that full autonomic node
   with a wide range description of ASA can require high forwarding plane
   performance in the ACP, for example for telemetry, but RPL profile that
   determination is for future work.  Implementations of ACP nodes need
   to solely support traditional/SDN style use cases can benefit by default.  The format of this section is derived from ACP at lower
   performance, especially if
   draft-ietf-roll-applicability-template.

6.11.1.1.  Summary

   In summary, the ACP is used only profile chosen for critical
   operations, e.g.: when the data-plane RPL is not available.  See
   [I-D.ietf-anima-stable-connectivity] for more details.

6.12.2.  Addressing of Secure Channels in the data-plane

   In order to one that expects a fairly
   reliable network reasonably fast links so that RPL convergence will
   be independent triggered immediately upon recognition of the data-plane configuration link failure/recovery.

   The key limitation of global
   IPv6 subnet addresses (that may not exist when the ACP chosen profile is brought
   up), Link-local secure channels MUST use IPv6 link local addresses
   between adjacent neighbors.  The fully autonomic mechanisms in this
   document only specify these link-local secure channels.  Section 8.2
   specifies extensions in which secure channels are tunnels.  For
   those, this requirement does not apply.

   The Link-local secure channels specified in this document therefore
   depend on basic IPv6 link-local functionality that it is designed to be auto-enabled by
   not require any Data-Plane artifacts (such as [RFC6553]).  While the
   senders/receivers of ACP and prohibiting the data-plane from disabling it.  The packets can be legacy NOC devices connected
   via ACP
   also depends on being able connect (see Section 8.1.1 to operate the secure channel protocol
   (e.g.: IPsec / dTLS) across IPv6 link-local addresses, something that
   may ACP, their connectivity can
   be an uncommon profile.  Functionally, these are handled as non-RPL-aware leafs (or "Internet") according to the only
   interactions with
   Data-Plane architecture explained in [I-D.ietf-roll-useofrplinfo].
   This non-artifact profile is largely driven by the data-plane that desire to avoid
   introducing the required Hop-by-Hop headers into the ACP needs forwarding
   plane, especially to have.

   To mitigate these interactions support devices with the data-plane, extensions to silicon forwarding planes
   that can not support insertion/removal of these headers in silicon.

   In this document may specify additional layer 2 or layer encapsulations
   for profile choice, RPL has no Data-Plane artifacts.  A simple
   destination prefix based upon the routing table is used.  A
   consequence of supporting only a single instanceID that is containing
   one Destination Oriented Directed Acyclic Graph (DODAG), the ACP secure channels as well as other protocols will
   only accommodate only a single class of routing table and cannot
   create optimized routing paths to auto-discover
   peer endpoints for such encapsulations (e.g.: tunneling across L3 accomplish latency or
   use energy goals.

   Consider a network that has multiple NOCs in different locations.
   Only one NOC will become the DODAG root.  Other NOCs will have to
   send traffic through the DODAG (tree) rooted in the primary NOC.
   Depending on topology, this can be an annoyance from a latency point
   of L2 only encapsulations).

6.12.3.  MTU view, but it does not represent a single point of failure, as the
   DODAG can reconfigure itself when it detects data plane forwarding
   failures.

   The MTU lack of RPL Packet Information (RPI, the IPv6 header for ACP secure channels must RPL
   defined by [RFC6553]), means that the Data-Plane will have no rank
   value that can be derived locally from used to detect loops.  As a result, traffic may
   loop until the
   underlying link MTU minus TTL of the secure channel encapsulation overhead.

   ACP secure Channel protocols packet reaches zero.  This the same
   behavior as that of other IGPs that do not need to perform MTU discovery
   because they are built across L2 adjacencies - have the MTU on both sides
   connecting to Data-Plane
   options as RPL.

   Since links in the L2 connection ACP are assumed to be consistent.
   Extensions to ACP where the ACP mostly reliable (or have
   link layer protection against loss) and because there is for example tunneled need to
   consider how no stretch
   according to guarantee MTU consistency.  This is Section 6.11.1.7, loops should be exceedingly rare
   though.

   There are a standard issue
   with tunneling, not specific to running the ACP across it.  Transport
   stacks running across ACP can perform normal PMTUD (Path MTU
   Discovery).  Because the ACP is meant variety of mechanisms possible in RPL to further avoid
   temporary loops: DODAG Information Objects (DIOs) SHOULD be prioritize reliability
   over performance, they MAY opt to only expect IPv6 minimum MTU (1280) sent
   2...3 times to avoid running into PMTUD implementation bugs or underlying link
   MTU mismatch problems.

6.12.4.  Multiple links between nodes

   If two nodes are connected via several links, inform children when losing the ACP last parent.  The
   technique in [RFC6550] section 8.2.2.6.  (Detaching) SHOULD be
   established across every link, but
   favored over that in section 8.2.2.5., (Poisoning) because it is possible allows
   local connectivity.  Nodes SHOULD select more than one parent, at
   least 3 if possible, and send Destination Advertisement Objects
   (DAO)s to establish the
   ACP only on a sub-set all of links.  Having an then in parallel.

   Additionally, failed ACP channel on every link
   has tunnels will be detected by IKEv2 Dead Peer
   Detection (which can function as a number of advantages, for example it allows replacement for a faster
   failover in case of link failure, Low-power and
   Lossy Networks' (LLN's) Expected Transmission Count (ETX).  A failure
   of an ACP tunnel should signal the RPL control plane to pick a
   different parent.

   Future Extensions to this RPL profile can provide optimality for
   multiple NOCs.  This requires utilizing Data-Plane artifact including
   IPinIP encap/decap on ACP routers and processing of IPv6 RPI headers.
   Alternatively, (Src,Dst) routing table entries could be used.  A
   decision for the preferred technology would have to be done when such
   extension is defined.

6.11.1.2.  RPL Instances

   Single RPL instance.  Default RPLInstanceID = 0.

6.11.1.3.  Storing vs. Non-Storing Mode

   RPL Mode of Operations (MOP): MUST support mode 2 - "Storing Mode of
   Operations with no multicast support".  Implementations MAY support
   mode 3 ("... with multicast support" as that is a superset of mode
   2).  Note: Root indicates mode in DIO flow.

6.11.1.4.  DAO Policy

   Proactive, aggressive DAO state maintenance:

   o  Use K-flag in unsolicited DAO indicating change from previous
      information (to require DAO-ACK).

   o  Retry such DAO DAO-RETRIES(3) times with DAO- ACK_TIME_OUT(256ms)
      in between.

6.11.1.5.  Path Metric

   Hopcount.

6.11.1.6.  Objective Function

   Objective Function (OF): Use OF0 [RFC6552].  No use of metric
   containers.

   rank_factor: Derived from link speed: <= 100Mbps:
   LOW_SPEED_FACTOR(5), else HIGH_SPEED_FACTOR(1)

6.11.1.7.  DODAG Repair

   Global Repair: we assume stable links and ranks (metrics), so no need
   to periodically rebuild DODAG.  DODAG version only incremented under
   catastrophic events (e.g., administrative action).

   Local Repair: As soon as link breakage is detected, send No-Path DAO
   for all the targets that where reachable only via this link.  As soon
   as link repair is detected, validate if this link provides you a
   better parent.  If so, compute your new rank, and send new DIO that
   advertises your new rank.  Then send a DAO with a new path sequence
   about yourself.

   stretch_rank: none provided ("not stretched").

   Data Path Validation: Not used.

   Trickle: Not used.

6.11.1.8.  Multicast

   Not used yet but possible because of the selected mode of operations.

6.11.1.9.  Security

   [RFC6550] security not used, substituted by ACP security.

6.11.1.10.  P2P communications

   Not used.

6.11.1.11.  IPv6 address configuration

   Every ACP node (RPL node) announces an IPv6 prefix covering the
   address(es) used in the ACP node.  The prefix length depends on the
   chosen addressing sub-scheme of the ACP address provisioned into the
   certificate of the ACP node, e.g., /127 for Zone Addressing Sub-
   Scheme or /112 or /120 for Vlong addressing sub-scheme.  See
   Section 6.10 for more details.

   Every ACP node MUST install a black hole (aka null) route for
   whatever ACP address space that it advertises (i.e.: the /96 or
   /127).  This is avoid routing loops for addresses that an ACP node
   has not (yet) used.

6.11.1.12.  Administrative parameters

   Administrative Preference ([RFC6550], 3.2.6 - to become root):
   Indicated in DODAGPreference field of DIO message.

   o  Explicit configured "root": 0b100

   o  ACP registrar (Default): 0b011

   o  ACP-connect (non-registrar): 0b010

   o  Default: 0b001.

6.11.1.13.  RPL Data-Plane artifacts

   RPI (RPL Packet Information [RFC6553]): Not used as there is only a
   single instance, and data path validation is not being used.

   SRH (RPL Source Routing - RFC6552): Not used.  Storing mode is being
   used.

6.11.1.14.  Unknown Destinations

   Because RPL minimizes the size of the routing and forwarding table,
   prefixes reachable through the same interface as the RPL root are not
   known on every ACP node.  Therefore traffic to unknown destination
   addresses can only be discovered at the RPL root.  The RPL root
   SHOULD have attach safe mechanisms to operationally discover and log
   such packets.

6.12.  General ACP Considerations

   Since channels are by default established between adjacent neighbors,
   the resulting overlay network does hop by hop encryption.  Each node
   decrypts incoming traffic from the ACP, and encrypts outgoing traffic
   to its neighbors in the ACP.  Routing is discussed in Section 6.11.

6.12.1.  Performance

   There are no performance requirements against ACP implementations
   defined in this document because the performance requirements depend
   on the intended use case.  It is expected that full autonomic node
   with a wide range of ASA can require high forwarding plane
   performance in the ACP, for example for telemetry, but that
   determination is for future work.  Implementations of ACP to solely
   support traditional/SDN style use cases can benefit from ACP at lower
   performance, especially if the ACP is used only for critical
   operations, e.g., when the Data-Plane is not available.  See
   [RFC8368] for more details.

6.12.2.  Addressing of Secure Channels in the Data-Plane

   In order to be independent of the Data-Plane configuration of global
   IPv6 subnet addresses (that may not exist when the ACP is brought
   up), Link-local secure channels MUST use IPv6 link local addresses
   between adjacent neighbors.  The fully autonomic mechanisms in this
   document only specify these link-local secure channels.  Section 8.2
   specifies extensions in which secure channels are tunnels.  For
   those, this requirement does not apply.

   The Link-local secure channels specified in this document therefore
   depend on basic IPv6 link-local functionality to be auto-enabled by
   the ACP and prohibiting the Data-Plane from disabling it.  The ACP
   also depends on being able to operate the secure channel protocol
   (e.g., IPsec / DTLS) across IPv6 link-local addresses, something that
   may be an uncommon profile.  Functionally, these are the only
   interactions with the Data-Plane that the ACP needs to have.

   To mitigate these interactions with the Data-Plane, extensions to
   this document may specify additional layer 2 or layer encapsulations
   for ACP secure channels as well as other protocols to auto-discover
   peer endpoints for such encapsulations (e.g., tunneling across L3 or
   use of L2 only encapsulations).

6.12.3.  MTU

   The MTU for ACP secure channels must be derived locally from the
   underlying link MTU minus the secure channel encapsulation overhead.

   ACP secure Channel protocols do not need to perform MTU discovery
   because they are built across L2 adjacencies - the MTU on both sides
   connecting to the L2 connection are assumed to be consistent.
   Extensions to ACP where the ACP is for example tunneled need to
   consider how to guarantee MTU consistency.  This is an issue of
   tunnels, not an issue of running the ACP across a tunnel.  Transport
   stacks running across ACP can perform normal PMTUD (Path MTU
   Discovery).  Because the ACP is meant to be prioritize reliability
   over performance, they MAY opt to only expect IPv6 minimum MTU (1280)
   to avoid running into PMTUD implementation bugs or underlying link
   MTU mismatch problems.

6.12.4.  Multiple links between nodes

   If two nodes are connected via several links, the ACP SHOULD be
   established across every link, but it is possible to establish the
   ACP only on a sub-set of links.  Having an ACP channel on every link
   has a number of advantages, for example it allows for a faster
   failover in case of link failure, and it reflects the physical
   topology more closely.  Using a subset subset of links (for example, a
   single link), reduces resource consumption on the node, because state
   needs to be kept per ACP channel.  The negotiation scheme explained
   in Section 6.5 allows Alice (the node with the higher ACP address) to
   drop all but the desired ACP channels to Bob - and Bob will not re-
   try to build these secure channels from his side unless Alice shows
   up with a previously unknown GRASP announcement (e.g., on a different
   link or with a different address announced in GRASP).

6.12.5.  ACP interfaces

   The ACP VRF has conceptually two type of interfaces: The "ACP
   Loopback interface(s)" to which the ACP ULA address(es) are assigned
   and the "ACP virtual interfaces" that are mapped to the ACP secure
   channels.

   The term "Loopback interface" was introduced initially to refer to an
   internal interface on a node that would allow IP traffic between
   transport endpoints on the node in the absence or failure of any or
   all external interfaces, see [RFC4291] section 2.5.3.

   Even though Loopback interfaces were originally designed to hold only
   Loopback addresses not reachable from outside the node, these
   interfaces are also commonly used today to hold addresses reachable
   from the outside.  They are meant to be reachable independent of any
   external interface being operational, and therefore to be more
   resilient.  These addresses on Loopback interfaces can be thought of
   as "node addresses" instead of "interface addresses", and that is
   what ACP address(es) are.  This construct makes it therefore possible
   to address ACP nodes with a well-defined set of addresses independent
   of the number of external interfaces.

   For these reason, the ACP (ULA) address(es) are assigned to Loopback
   interface(s).

   ACP secure channels, e.g., IPsec, DTLS or other future security
   associations with neighboring ACP nodes can be mapped to ACP virtual
   interfaces in different ways:

   ACP point-to-point virtual interface:

   Each ACP secure channel is mapped into a separate point-to-point ACP
   virtual interface.  If a physical subnet has more than two ACP
   capable nodes (in the same domain), this implementation approach will
   lead to a full mesh of links (for example, ACP virtual interfaces between them.

   ACP multi-access virtual interface:

   In a more advanced implementation approach, the ACP will construct a
   single link), reduces resource consumption on multi-access ACP virtual interface for all ACP secure channels
   to ACP capable nodes reachable across the node, because state
   needs same underlying (physical)
   subnet.  IPv6 link-local multicast packets sent into an ACP multi-
   access virtual interface are replicated to be kept per every ACP channel.  The negotiation scheme explained
   in Section 6.5 allows Alice (the node with secure channel
   mapped into the higher ACP address) multicast-access virtual interface.  IPv6 unicast
   packets sent into an ACP multi-access virtual interface are sent to
   drop all but
   the desired ACP channels secure channel that belongs to Bob - and Bob will not re-
   try the ACP neighbor that is the
   next-hop in the ACP forwarding table entry used to build these secure channels from his side unless Alice shows
   up with a previously unknown GRASP announcement (e.g.: reach the packets
   destination address.

   There is no requirement for all ACP nodes on the same multi-access
   subnet to use the same type of ACP virtual interface.  This is purely
   a different
   link or with a different address announced in GRASP).

6.12.5. node local decision.

   ACP nodes MUST perform standard IPv6 operations across ACP virtual
   interfaces

   The including SLAAC (Stateless Address Auto-Configuration) -
   [RFC4862]) to assign their IPv6 link local address on the ACP VRF has conceptually two type of interfaces: The "ACP
   loopback interface(s)" virtual
   interface and ND (Neighbor Discovery - [RFC4861]) to discover which
   IPv6 link-local neighbor address belongs to which ACP secure channel
   mapped to the ACP ULA address(es) are assigned
   and virtual interface.  This is independent of whether
   the "ACP ACP virtual interfaces" that are mapped interface is point-to-point or multi-access.

   "Optimistic Duplicate Address Detection (DAD)" according to [RFC4429]
   is RECOMMENDED because the likelihood for duplicates between ACP secure
   channels.

   The term "loopback interface" was introduced initially
   nodes is highly improbable as long as the address can be formed from
   a globally unique local assigned identifier (e.g., EUI-48/EUI-64, see
   below).

   ACP nodes MAY reduce the amount of link-local IPv6 multicast packets
   from ND by learning the IPv6 link-local neighbor address to refer ACP
   secure channel mapping from other messages such as the source address
   of IPv6 link-local multicast RPL messages - and therefore forego the
   need to an
   internal send Neighbor Solicitation messages.

   The ACP virtual interface on a IPv6 link local address can be derived from
   any appropriate local mechanism such as node that would allow IP traffic between
   transport endpoints local EUI-48 or EUI-64
   ("EUI" stands for "Extended Unique Identifier").  It MUST NOT depend
   on something that is attackable from the node in Data-Plane such as the absence or failure IPv6
   link-local address of any the underlying physical interface, which can be
   attacked by SLAAC, or
   all external interfaces, see [RFC4291] section 2.5.3.

   Even though loopback interfaces where originally designed to hold
   only loopback addresses parameters of the secure channel encapsulation
   header that may not reachable from outside be protected by the node, these
   interfaces are also commonly secure channel mechanism.

   The link-layer address of an ACP virtual interface is the address
   used today to hold addresses reachable
   from for the outside.  They underlying interface across which the secure tunnels are meant
   built, typically Ethernet addresses.  Because unicast IPv6 packets
   sent to be reachable independent of any
   external an ACP virtual interface being operational, and therefore are not sent to a link-layer
   destination address but rather an ACP secure channel, the link-layer
   address fields SHOULD be more
   resilient.  These addresses ignored on loopback interfaces can reception and instead the ACP
   secure channel from which the message was received should be thought
   remembered.

   Multi-access ACP virtual interfaces are preferable implementations
   when the underlying interface is a (broadcast) multi-access subnet
   because they do reflect the presence of
   as "node addresses" instead the underlying multi-access
   subnet into the virtual interfaces of "interface addresses", and that is
   what ACP address(es) are. the ACP.  This construct makes it therefore possible for
   example simpler to address ACP nodes build services with a well-defined set of addresses independent
   of topology awareness inside the number of external
   ACP VRF in the same way as they could have been built running
   natively on the multi-access interfaces.

   For these reason,

   Consider also the ACP (ULA) address(es) are assigned to loopback
   interface(s).

   ACP secure channels, e.g.: IPsec, dTLS or other future security
   associations impact of point-to-point vs. multi-access virtual
   interface on the efficiency of flooding via link local multicasted
   messages:

   Assume a LAN with neighboring three ACP nodes can be mapped to neighbors, Alice, Bob and Carol.  Alice's
   ACP virtual
   interfaces in different ways: GRASP wants to send a link-local GRASP multicast message to Bob
   and Carol.  If Alice's ACP emulates the LAN as one point-to-point
   virtual interface:

   Each interface to Bob and one to Carol, The sending applications
   itself will send two copies, if Alice's ACP secure channel is mapped into emulates a separate point-to-point LAN, GRASP
   will send one packet and the ACP
   virtual interface. will replicate it.  The result is
   the same.  The difference happens when Bob and Carol receive their
   packet.  If a physical subnet has more than two they use ACP
   capable nodes (in point-to-point virtual interfaces, their
   GRASP instance would forward the same domain), this implementation approach will
   lead packet from Alice to a full mesh each other as
   part of the GRASP flooding procedure.  These packets are unnecessary
   and would be discarded by GRASP on receipt as duplicates (by use of ACP virtual interfaces between them.

   ACP multi-access virtual interface:

   In a more advanced implementation approach,
   the GRASP Session ID).  If Bob and Charly's ACP will construct would emulate a
   single
   multi-access ACP virtual interface for all ACP secure channels interface, then this would not happen, because
   GRASPs flooding procedure does not replicate back packets to ACP capable nodes reachable across the same underlying (physical)
   subnet.  IPv6
   interface that they were received from.

   Note that link-local GRASP multicast packets messages are not sent directly
   as IPv6 link-local multicast UDP messages into an ACP multi-
   access virtual interface
   interfaces, but instead into ACP GRASP virtual interfaces, that are replicated to every
   layered on top of ACP secure channel
   mapped into the virtual interfaces to add TCP reliability to
   link-local multicast GRASP messages.  Nevertheless, these ACP multicast-access GRASP
   virtual interface.  IPv6 unicast
   packets sent into an interfaces perform the same replication of message and,
   therefore, result in the same impact on flooding.  See Section 6.8.2
   for more details.

   RPL does support operations and correct routing table construction
   across non-broadcast multi-access (NBMA) subnets.  This is common
   when using many radio technologies.  When such NBMA subnets are used,
   they MUST NOT be represented as ACP multi-access virtual interface are sent to interfaces
   because the replication of IPv6 link-local multicast messages will
   not reach all NBMA subnet neighbors.  In result, GRASP message
   flooding would fail.  Instead, each ACP secure channel that belongs to the across such an
   interface MUST be represented as a ACP neighbor that is the
   next-hop in point-to-point virtual
   interface.  These requirements can be avoided by coupling the ACP forwarding table entry used
   flooding mechanism for GRASP messages directly to reach the packets
   destination address.

   There RPL (flood GRASP
   across DODAG), but such an enhancement is no requirement subject for all ACP nodes on the same future work.

   Care must also be taken when creating multi-access
   subnet to use the same type of ACP virtual interface.  This is purely
   a node local decision.

   ACP nodes MUST perform standard IPv6 operations
   interfaces across ACP virtual
   interfaces including SLAAC (Stateless Address Auto-Configuration -
   [RFC4862]) to assign their IPv6 link local address on the secure channels between ACP virtual
   interface and ND (Neighbor Discovery - [RFC4861]) nodes in different
   domains or routing subdomains.  The policies to discover be negotiated may be
   described as peer-to-peer policies in which
   IPv6 link-local neighbor address belongs case it is easier to which
   create ACP point-to-point virtual interfaces for these secure channel
   mapped to the
   channels.

7.  ACP virtual interface.  This is independent support on L2 switches/ports (Normative)

7.1.  Why

       ANrtr1 ------ ANswitch1 --- ANswitch2 ------- ANrtr2
                 .../   \                   \  ...
       ANrtrM ------     \                   ------- ANrtrN
                          ANswitchM ...

                 Figure 12: Topology with L2 ACP switches

   Consider a large L2 LAN with ANrtr1...ANrtrN connected via some
   topology of whether L2 switches.  Examples include large enterprise campus
   networks with an L2 core, IoT networks or broadband aggregation
   networks which often have even a multi-level L2 switched topology.

   If the discovery protocol used for the ACP virtual interface is point-to-point or multi-access. operating at the subnet
   level, every ACP nodes MAY reduce router will see all other ACP routers on the amount LAN as
   neighbors and a full mesh of ACP channels will be built.  If some or
   all of link-local IPv6 multicast packets
   from ND by learning the IPv6 link-local neighbor address to AN switches are autonomic with the same discovery
   protocol, then the full mesh would include those switches as well.

   A full mesh of ACP connections like this can creates fundamental
   scale challenges.  The number of security associations of the secure
   channel mapping from protocols will likely not scale arbitrarily, especially when
   they leverage platform accelerated encryption/decryption.  Likewise,
   any other messages such ACP operations (such as routing) needs to scale to the source address
   number of IPv6 link-local multicast RPL messages - and therefore forego the
   need direct ACP neighbors.  An ACP router with just 4 physical
   interfaces might be deployed into a LAN with hundreds of neighbors
   connected via switches.  Introducing such a new unpredictable scaling
   factor requirement makes it harder to send Neighbor Solicitation messages. support the ACP nodes MUST NOT derive their on arbitrary
   platforms and in arbitrary deployments.

   Predictable scaling requirements for ACP virtual interface IPv6 link local
   address from their IPv6 link-local address used neighbors can most easily be
   achieved if in topologies like these, ACP capable L2 switches can
   ensure that discovery messages terminate on them so that neighboring
   ACP routers and switches will only find the underlying
   interface (e.g.: the address that is used physically connected ACP
   L2 switches as the encapsulation
   address in the their candidate ACP secure channel protocols defined neighbors.  With such a discovery
   mechanism in this
   document).  This ensures that place, the ACP virtual interface operations and its security associations will not depend on only
   need to scale to the specifics number of the encapsulation used by physical interfaces instead of a
   potentially much larger number of "LAN-connected" neighbors.  And the
   ACP
   secure channel and that attacks against SLAAC on the physical
   interface topology will not introduce new attack vectors against follow directly the physical topology, something
   which can then also be leveraged in management operations of or by ASAs.

   In the example above, consider ANswitch1 and ANswitchM are ACP virtual interface.
   capable, and ANswitch2 is not ACP capable.  The link-layer address of an desired ACP virtual interface topology
   is the address
   used for the underlying interface across which the secure tunnels are
   built, typically Ethernet addresses.  Because unicast IPv6 packets
   sent to that ANrtr1 and ANrtrM only have an ACP virtual interface are not sent connection to ANswitch1,
   and that ANswitch1, ANrtr2, ANrtrN have a link-layer
   destination address but rather full mesh of ACP connection
   amongst each other.  ANswitch1 also has an ACP secure channel, the link-layer
   address fields SHOULD be ignored on reception connection with
   ANswitchM and instead the ANswitchM has ACP
   secure channel from which the message was received should be
   remembered.

   Multi-access connections to anything else behind
   it.

7.2.  How (per L2 port DULL GRASP)

   To support ACP virtual on L2 switches or L2 switched ports of an L3 device,
   it is necessary to make those L2 ports look like L3 interfaces are preferable implementations
   when for
   the underlying interface is a (broadcast) multi-access subnet
   because they do reflect ACP implementation.  This primarily involves the presence creation of a
   separate DULL GRASP instance/domain on every such L2 port.  Because
   GRASP has a dedicated link-local IPv6 multicast address
   (ALL_GRASP_NEIGHBORS), it is sufficient that all packets for this
   address are being extracted at the underlying multi-access
   subnet into port level and passed to that DULL
   GRASP instance.  Likewise the virtual interfaces of IPv6 link-local multicast packets sent
   by that DULL GRASP instance need to be sent only towards the ACP.  This makes it L2 port
   for
   example simpler to build services this DULL GRASP instance.

   If the device with topology awareness inside L2 ports is supporting per L2 port ACP DULL GRASP
   as well as MLD snooping ([RFC4541]), then MLD snooping must be
   changed to never forward packets for ALL_GRASP_NEIGHBORS because that
   would cause the problem that per L2 port ACP VRF DULL GRASP is meant to
   overcome (forwarding DULL GRASP packets across L2 ports).

   The rest of ACP operations can operate in the same way as they could have been built running
   natively on the multi-access interfaces.

   Consider also in L3
   devices: Assume for example that the impact of point-to-point vs. multi-access virtual
   interface device is an L3/L2 hybrid device
   where L3 interfaces are assigned to VLANs and each VLAN has
   potentially multiple ports.  DULL GRASP is run as described
   individually on the efficiency of flooding via link local multicasted
   messages:

   Assume each L2 port.  When it discovers a LAN with three candidate ACP neighbors, Alice, Bob
   neighbor, it passes its IPv6 link-local address and Carol.  Alice's supported secure
   channel protocols to the ACP GRASP wants secure channel negotiation that can be
   bound to send a the L3 (VLAN) interface.  It will simply use link-local GRASP IPv6
   multicast message packets to Bob
   and Carol.  If Alice's the candidate ACP emulates neighbor.  Once a secure
   channel is established to such a neighbor, the LAN as one point-to-point virtual interface to Bob
   which this secure channel is mapped should then actually be the L2
   port and one not the L3 interface to Carol, The sending applications
   itself will send two copies, if Alice's best map the actual physical
   topology into the ACP emulates virtual interfaces.  See Section 6.12.5 for
   more details about how to map secure channels into ACP virtual
   interfaces.  Note that a LAN, GRASP
   will send one packet and the single L2 port can still have multiple ACP will replicate it.  The result is
   the same.
   neighbors if it connect for example to multiple ACP neighbors via a
   non-ACP enabled switch.  The difference happens when Bob and Carol receive their
   packet.  If they use per L2 port ACP point-to-point virtual interfaces, their
   GRASP instance would forward the packet from Alice to each other as
   part of interface can
   therefore still be a multi-access virtual LAN.

   For example, in the GRASP flooding procedure.  These packets are unnecessary
   and above picture, ANswitch1 would be discarded by run separate DULL
   GRASP instances on receipt as duplicates (by use of its ports to ANrtr1, ANswitch2 and ANswitchI, even
   though all those three ports may be in the GRASP Session ID).  If Bob data plane in the same
   (V)LAN and Charlies ACP would emulate a
   multi-access virtual interface, then this perform L2 switching between these ports, ANswitch1 would not happen, because
   GRASPs flooding procedure does not replicate back packets to
   perform ACP L3 routing between them.

   The description in the
   interface previous paragraph was specifically meant to
   illustrate that they were received from.

   Note on hybrid L3/L2 devices that link-local GRASP multicast messages are not sent directly
   as IPv6 common in
   enterprise, IoT and broadband aggregation, there is only the GRASP
   packet extraction (by Ethernet address) and GRASP link-local
   multicast UDP messages into ACP virtual
   interfaces, but instead into ACP GRASP virtual interfaces, per L2-port packet injection that has to consider L2 ports
   at the hardware forwarding level.  The remaining operations are
   layered on top
   purely ACP control plane and setup of secure channels across the L3
   interface.  This hopefully makes support for per-L2 port ACP virtual interfaces to add TCP reliability on those
   hybrid devices easy.

   This L2/L3 optimized approach is subject to
   link-local multicast GRASP messages.  Nevertheless, these ACP GRASP
   virtual interfaces perform the same replication "address stealing", e.g.,
   where a device on one port uses addresses of message and,
   therefore, result a device on another
   port.  This is a generic issue in the same impact L2 LANs and switches often already
   have some form of "port security" to prohibit this.  They rely on flooding.  See Section 6.8.2
   for more details.

   RPL does support operations NDP
   or DHCP learning of which port/MAC-address and correct routing table construction
   across non-broadcast multi-access (NBMA) subnets. IPv6 address belong
   together and block duplicates.  This is common
   when using many radio technologies.  When such NBMA subnets are used,
   they MUST NOT be represented as ACP multi-access virtual interfaces
   because type of function needs to be
   enabled to prohibit DoS attacks.  Likewise the GRASP DULL instance
   needs to ensure that the replication of IPv6 link-local multicast messages will
   not reach all NBMA subnet neighbors.  In result, address in the locator-option matches
   the source IPv6 address of the DULL GRASP message
   flooding would fail.  Instead, each ACP secure channel across packet.

   In devices without such an
   interface MUST be represented a mix of L2 port/interfaces and L3 interfaces
   (to terminate any transport layer connections), implementation
   details will differ.  Logically most simply every L2 port is
   considered and used as a separate L3 subnet for all ACP point-to-point virtual
   interface.  These requirements can be avoided by coupling operations.
   The fact that the ACP
   flooding mechanism only requires IPv6 link-local unicast and
   multicast should make support for GRASP messages directly to RPL (flood GRASP
   across DODAG), it on any type of L2 devices as
   simple as possible, but such an enhancement is subject for future work.

   Care must also be taken when creating multi-access ACP virtual
   interfaces across ACP secure channels between ACP nodes in different
   domains or routing subdomains.  The policies the need to be negotiated support secure channel protocols
   may be
   described as peer-to-peer policies in which case it is easier a limiting factor to
   create ACP point-to-point virtual interfaces for these secure
   channels.

7. supporting ACP support on L2 switches/ports (Normative)

7.1.  Why

       ANrtr1 ------ ANswitch1 --- ANswitch2 ------- ANrtr2
                 .../   \                   \  ...
       ANrtrM ------     \                   ------- ANrtrN
                          ANswitchM ...

                                 Figure 7

   Consider a large L2 LAN such devices.  Future
   options such as MacSec could improve that situation.

   A generic issue with ANrtr1...ANrtrN connected via some
   topology of ACP in L2 switches.  Examples include large enterprise campus switched networks is the interaction
   with an L2 core, IoT networks or broadband aggregation
   networks which often have even a multi-level L2 switched topology.

   If the discovery protocol used for Spanning Tree Protocol.  Ideally, the ACP is operating at should be built
   also across ports that are blocked in STP so that the subnet
   level, every ACP router will see all other ACP routers does not
   depend on the LAN as
   neighbors STP and a full mesh of ACP channels will can continue to run unaffected across STP topology
   changes (where re-convergence can be built.  If some or
   all of the AN switches quite slow).  The above
   described simple implementation options are autonomic with not sufficient for this.
   Instead they would simply have the same discovery
   protocol, then ACP run across the full mesh active STP
   topology and the ACP would include those switches as well.

   A full mesh of equally be interrupted and re-converge
   with STP changes.

8.  Support for Non-ACP Components (Normative)

8.1.  ACP connections like this can creates fundamental
   scale challenges. Connect

8.1.1.  Non-ACP Controller / NMS system

   The number of security associations Autonomic Control Plane can be used by management systems, such
   as controllers or network management system (NMS) hosts (henceforth
   called simply "NMS hosts"), to connect to devices (or other type of
   nodes) through it.  For this, an NMS host must have access to the secure
   channel protocols will likely not scale arbitrarily, especially when
   they leverage platform accelerated encryption/decryption.  Likewise,
   any other
   ACP.  The ACP operations (such as routing) needs is a self-protecting overlay network, which allows by
   default access only to scale trusted, autonomic systems.  Therefore, a
   traditional, non-ACP NMS system does not have access to the
   number of direct ACP neighbors.  An ACP router with by
   default, just 4 physical
   interfaces might be deployed into a LAN with hundreds of neighbors
   connected via switches.  Introducing such a new unpredictable scaling
   factor requirement makes like any other external node.

   If the NMS host is not autonomic, i.e., it harder to does not support autonomic
   negotiation of the ACP on arbitrary
   platforms and in arbitrary deployments.

   Predictable scaling requirements for ACP neighbors ACP, then it can most easily be
   achieved if in topologies like these, ACP capable L2 switches can
   ensure that discovery messages terminate on them so that neighboring
   ACP routers and switches will only find brought into the physically connected ACP
   L2 switches as their candidate by
   explicit configuration.  To support connections to adjacent non-ACP
   nodes, an ACP neighbors.  With such node must support "ACP connect" (sometimes also called
   "autonomic connect"):

   "ACP connect" is a discovery
   mechanism in place, the ACP and its security associations will only
   need to scale to the number of physical function on an autonomic node that is called an
   "ACP edge node".  With "ACP connect", interfaces instead of a
   potentially much larger number of "LAN-connected" neighbors.  And the
   ACP topology will follow directly on the physical topology, something
   which node can then also be leveraged in management operations or by ASAs.

   In
   configured to be put into the example above, consider ANswitch1 and ANswitchM are ACP
   capable, and ANswitch2 is not ACP capable. VRF.  The desired ACP topology is that ANrtr1 and ANrtrM only have an ACP connection then accessible to ANswitch1,
   and that ANswitch1, ANrtr2, ANrtrN have a full mesh of ACP connection
   amongst each other.  ANswitch1 also has
   other (NOC) systems on such an ACP connection with
   ANswitchM and ANswitchM has ACP connections interface without those systems having
   to anything else behind
   it.

7.2.  How (per L2 port DULL GRASP)

   To support any ACP on L2 switches discovery or L2 switched ports of an L3 device,
   it is necessary to make those L2 ports look like L3 interfaces for
   the ACP implementation. channel setup.  This primarily involves the creation of a
   separate DULL GRASP instance/domain on every such L2 port.  Because
   GRASP has a dedicated link-local IPv6 multicast address
   (ALL_GRASP_NEIGHBORS), it is sufficient that all packets for this
   address are being extracted at the port level and passed also
   called "native" access to that DULL
   GRASP instance.  Likewise the IPv6 link-local multicast packets sent
   by that DULL GRASP instance need ACP because to be sent only towards the L2 port
   for this DULL GRASP instance.

   If those (NOC) systems the device with L2 ports is supporting per L2 port
   interface looks like a normal network interface (without any
   encryption/novel-signaling).

                                   Data-Plane "native" (no ACP)
                                            .
  +--------+       +----------------+       .         +-------------+
  | ACP    |       |ACP Edge Node   |       .         |             |
  | Node   |       |                |       v         |             |
  |        |-------|...[ACP VRF]....+-----------------|             |+
  |        |   ^   |.               |                 | NOC Device  ||
  |        |   .   | .[Data-Plane]..+-----------------| "NMS hosts" ||
  |        |   .   |  [          ]  | .          ^    |             ||
  +--------+   .   +----------------+  .         .    +-------------+|
               .                        .        .     +-------------+
               .                        .        .
            Data-Plane "native"         .     ACP "native" (unencrypted)
          + ACP auto-negotiated         .    "ACP connect subnet"
            and encrypted               .
                                        ACP DULL GRASP
   as well as MLD snooping ([RFC4541]), then MLD snooping must be
   changed to never forward packets for ALL_GRASP_NEIGHBORS because that
   would cause the problem that per L2 port connect interface
                                        e.g., "vrf ACP DULL GRASP is meant native" (config)

                          Figure 13: ACP connect

   ACP connect has security consequences: All systems and processes
   connected via ACP connect have access to
   overcome (forwarding DULL GRASP packets across L2 ports).

   The rest of all ACP operations can operate in nodes on the same way as in L3
   devices: Assume for example that entire
   ACP, without further authentication.  Thus, the device is an L3/L2 hybrid device
   where L3 interfaces are assigned to VLANs and each VLAN has
   potentially multiple ports.  DULL GRASP is run as described
   individually on each L2 port.  When it discovers a candidate ACP
   neighbor, it passes its IPv6 link-local address connect interface
   and supported secure
   channel protocols (NOC) systems connected to the ACP secure channel negotiation that can it must be
   bound to physically controlled/
   secured.  For this reason the L3 (VLAN) interface.  It will simply use link-local IPv6
   multicast packets mechanisms described here do explicitly
   not include options to the candidate ACP neighbor.  Once allow for a secure
   channel is established non-ACP router to be connected
   across an ACP connect interface and addresses behind such a neighbor, router
   routed inside the virtual ACP.

   An ACP connect interface provides exclusively access to
   which this secure channel only the ACP.
   This is mapped should then actually be likely insufficient for many NMS hosts.  Instead, they would
   require a second "Data-Plane" interface outside the L2
   port and not ACP for
   connections between the L3 interface NMS host and administrators, or Internet
   based services, or for direct access to best map the actual physical
   topology into the ACP virtual interfaces.  See Section 6.12.5 Data-Plane.  The document
   "Using Autonomic Control Plane for Stable Connectivity of Network
   OAM" [RFC8368] explains in more details about detail how to map secure channels into the ACP virtual
   interfaces.  Note that a single L2 port can still have multiple ACP
   neighbors if it connect for example to multiple ACP neighbors via be integrated
   in a
   non-ACP enabled switch. mixed NOC environment.

   The per L2 port ACP virtual connect interface can
   therefore still must be a multi-access virtual LAN.

   For example, in the above picture, ANswitch1 would run separate DULL
   GRASP instances on its ports to ANrtr1, ANswitch2 and ANswitchI, even
   though all those three ports may (auto-)configured with an IPv6
   address prefix.  Is prefix SHOULD be in covered by one of the data plane (ULA)
   prefix(es) used in the same
   (V)LAN and perform L2 switching between these ports, ANswitch1 would
   perform ACP L3 routing between them.

   The description in ACP.  If using non-autonomic configuration, it
   SHOULD use the previous paragraph was specifically meant to
   illustrate that on hybrid L3/L2 devices ACP Manual Addressing Sub-Scheme (Section 6.10.4).  It
   SHOULD NOT use a prefix that are common in
   enterprise, IoT and broadband aggregation, there is only also routed outside the GRASP
   packet extraction (by Ethernet address) and GRASP link-local
   multicast per L2-port packet injection ACP so that has to consider L2 ports
   at
   the hardware forwarding level.  The remaining operations are
   purely addresses clearly indicate whether it is used inside the ACP control plane and setup or
   not.

   The prefix of secure channels across ACP connect subnets MUST be distributed by the L3
   interface.  This hopefully makes support for per-L2 port ACP on those
   hybrid devices easy.

   This L2/L3 optimized approach is subject edge
   node into the ACP routing protocol (RPL).  The NMS hosts MUST connect
   to "address stealing", e.g.: prefixes in the ACP routing table via its ACP connect interface.
   In the simple case where a device on one port the ACP uses addresses of a device on another
   port.  This is a generic issue in L2 LANs only one ULA prefix and switches often already all ACP
   connect subnets have some form of "port security" to prohibit this.  They prefixes covered by that ULA prefix, NMS hosts
   can rely on NDP
   or DHCP learning of which port/MAC-address and IPv6 address belong
   together and block duplicates.  This type of function needs to be
   enabled to prohibit DoS attacks.  Likewise [RFC6724] - The NMS host will select the GRASP DULL instance
   needs to ensure that ACP connect
   interface because any ACP destination address is best matched by the IPv6
   address in on the locator-option matches ACP connect interface.  If the source IPv6 address of NMS hosts ACP connect
   interface uses another prefix or if the DULL GRASP packet.

   In devices without such a mix of L2 port/interfaces and L3 interfaces
   (to terminate any transport layer connections), implementation
   details will differ.  Logically most simply every L2 port is
   considered and used as a separate L3 subnet for all ACP operations.
   The fact that uses multiple ULA
   prefixes, then the NMS hosts require (static) routes towards the ACP
   interface.

   ACP Edge Nodes MUST only requires forward IPv6 link-local unicast and
   multicast should make support for it on any type of L2 devices as
   simple as possible, but packets received from an ACP
   connect interface into the need ACP that has an IPv6 address from the ACP
   prefix assigned to support secure channel protocols
   may this interface (sometimes called "RPF filtering").
   This MAY be changed through administrative measures.

   To limit the security impact of ACP connect, nodes supporting it
   SHOULD implement a limiting factor security mechanism to supporting allow configuration/use of
   ACP connect interfaces only on such devices.  Future
   options such nodes explicitly targeted to be
   deployed with it (such as 802.1ae those physically secure locations like a
   NOC).  For example, the certificate of such node could improve include an
   extension required to permit configuration of ACP connect interfaces.
   This prohibits that situation.

   A generic issue with a random ACP in L2 switched networks is the interaction node with the Spanning Tree Protocol.  Ideally, the ACP should be built
   also across ports that are blocked in STP so easy physical access that the ACP does
   is not
   depend on STP and can continue meant to run unaffected across STP topology
   changes (where re-convergence can be quite slow).  The above
   described simple implementation options are not sufficient for this.
   Instead they would simply have the ACP run across the active STP
   topology and connect could start leaking the ACP would equally be interrupted when it
   becomes compromised and re-converge
   with STP changes.

8.  Support for Non-ACP Components (Normative)

8.1. the intruder configures ACP Connect

8.1.1.  Non-ACP Controller / NMS system

   The Autonomic Control Plane can be used by management systems, such
   as controllers or network management system (NMS) hosts (henceforth
   called simply "NMS hosts"), to connect to devices (or other type of
   nodes) through on it.  For this,
   The full workflow including the mechanism by which an NMS host must have access ACP registrar
   would select which node to the
   ACP. give such a certificate to is subject to
   future work.

8.1.2.  Software Components

   The ACP is a self-protecting overlay network, which allows by
   default access connect mechanism be only be used to trusted, autonomic systems.  Therefore, a
   traditional, non-ACP NMS system does not have access connect physically
   external systems (NMS hosts) to the ACP by
   default, just like any but also other external node.

   If applications,
   containers or virtual machines.  In fact, one possible way to
   eliminate the NMS host is not autonomic, i.e., it does not support autonomic
   negotiation security issue of the ACP, then it can be brought into the ACP by
   explicit configuration.  To support connections to adjacent non-ACP
   nodes, an external ACP node must support "ACP connect" (sometimes also connect
   "autonomic connect"):

   "ACP connect" interface is a function on
   to collocate an autonomic ACP edge node that is called and an
   "ACP edge node".  With "ACP connect", interfaces on NMS host by making one a virtual
   machine or container inside the node can be
   configured to be put into other; and therefore converting the
   unprotected external ACP VRF.  The subnet into an internal virtual subnet in a
   single device.  This would ultimately result in a fully ACP enabled
   NMS host with minimum impact to the NMS hosts software architecture.
   This approach is then accessible not limited to
   other (NOC) systems on such an interface without those systems having NMS hosts but could equally be
   applied to support any ACP discovery devices consisting of one or more VNF (virtual network
   functions): An internal virtual subnet connecting out-of-band
   management interfaces of the VNFs to an ACP channel setup.  This edge router VNF.

   The core requirement is also
   called "native" access to that the ACP because software components need to those (NOC) systems the
   interface looks like have a normal
   network interface (without any
   encryption/novel-signaling).

                                   data-plane "native" (no ACP)
                                            .
  +--------+       +----------------+       .         +-------------+
  | ACP    |       |ACP Edge Node   |       .         |             |
  | Node   |       |                |       v         |             |
  |        |-------|...[ACP VRF]....+-----------------|             |+
  |        |   ^   |.               |                 | NOC Device  ||
  |        |   .   | .[data-plane]..+-----------------| "NMS hosts" ||
  |        |   .   |  [   VRF    ]  | .          ^    |             ||
  +--------+   .   +----------------+  .         .    +-------------+|
               .                        .        .     +-------------+
               .                        .        .
            data-plane "native"         .     ACP "native" (unencrypted)
          + ACP auto-negotiated         .    "ACP connect subnet"
            and encrypted               .
                                        ACP connect interface
                                        e.g.: "vrf ACP native" (config)

                           Figure 8: ACP connect

   ACP connect has security consequences: All systems and processes
   connected via ACP connect have stack that permits access to all ACP nodes on the entire
   ACP, without further authentication.  Thus, the ACP connect interface and (NOC) systems connected to it must be physically controlled/
   secured.  For this reason optionally also the mechanisms described here do explicitly
   not include options to allow
   Data-Plane.  Like in the physical setup for a non-ACP router to NMS hosts this can be connected
   across an
   realized via two internal virtual subnets.  One that is connecting to
   the ACP connect interface and addresses behind such (which could be a router
   routed inside container or virtual machine by itself),
   and one (or more) connecting into the ACP.

   An Data-Plane.

   This "internal" use of ACP connect interface provides exclusively access approach should not considered to only the ACP.
   This
   be a "workaround" because in this case it is likely insufficient for many possible to build a
   correct security model: It is not necessary to rely on unprovable
   external physical security mechanisms as in the case of external NMS
   hosts.  Instead, they would
   require a second "data-plane" interface outside the ACP for
   connections between orchestration of the NMS host and administrators, or Internet
   based services, or for direct access to ACP, the data-plane.  The document
   "Autonomic Network Stable Connectivity"
   [I-D.ietf-anima-stable-connectivity] explains in more detail how virtual subnets
   and the
   ACP software components can be integrated in a mixed NOC environment.

   The ACP connect interface must done by trusted software that
   could be (auto-)configured with an IPv6
   address prefix.  Is prefix SHOULD considered to be covered by one part of the (ULA)
   prefix(es) used in the ACP.  If using non-autonomic configuration, it
   SHOULD use the ACP Manual Addressing Sub-Scheme (Section 6.10.4).  It
   SHOULD NOT use a prefix that ANI (or even an extended ACP).
   This software component is also routed outside the ACP so responsible for ensuring that only trusted
   software components will get access to that virtual subnet and that
   only even more trusted software components will get access to both
   the addresses clearly indicate whether it is used inside ACP virtual subnet and the Data-Plane (because those ACP or
   not. users
   could leak traffic between ACP and Data-Plane).  This trust could be
   established for example through cryptographic means such signed
   software packages.  The prefix specification of ACP connect subnets MUST these mechanisms is subject
   to future work.

   Note that ASA (Autonomic Software Agents) could also be distributed by the software
   components as described in this section, but further details of ASAs
   are subject to future work.

8.1.3.  Auto Configuration

   ACP edge
   node into the ACP routing protocol (RPL).  The nodes, NMS hosts MUST connect
   to prefixes and software components that as described
   in the ACP routing table previous section are meant to be composed via its ACP connect interface.
   In the simple case where virtual
   interfaces SHOULD support on the ACP uses only one ULA prefix and all ACP connect subnets have prefixes covered by that ULA prefix, NMS hosts
   can rely on [RFC6724] subnet StateLess Address
   Autoconfiguration (SLAAC - [RFC4862]) and route auto configuration
   according to [RFC4191].

   The NMS host will select the ACP connect
   interface because any ACP destination address is best matched by edge node acts as the
   address router on the ACP connect interface.  If subnet,
   providing the NMS hosts ACP connect
   interface uses another (auto-)configured prefix or if for the ACP uses multiple ULA
   prefixes, then the connect subnet to
   NMS hosts require (static) routes towards the ACP
   interface.

   ACP Edge Nodes MUST only forward IPv6 packets received from an ACP
   connect interface into the ACP that has an IPv6 address from the and/or software components.  The ACP edge node uses route
   prefix assigned to this interface (sometimes called "RPF filtering").
   This MAY be changed through administrative measures.

   To limit the security impact of ACP connect, nodes supporting it
   SHOULD implement a security mechanism to allow configuration/use of
   ACP connect interfaces only on nodes explicitly targeted to be
   deployed with it (such as those physically secure locations like a
   NOC).  For example, the certificate option of such node could include an
   extension required RFC4191 to permit configuration announce the default route (::/) with a
   lifetime of 0 and aggregated prefixes for routes in the ACP connect interfaces. routing
   table with normal lifetimes.  This prohibits will ensure that a random the ACP edge node with easy physical access that
   is
   does not meant become a default router, but that the NMS hosts and software
   components will route the prefixes used in the ACP to run the ACP connect could start leaking edge
   node.

   Aggregated prefix means that the ACP when it
   becomes compromised and edge node needs to only announce
   the /48 ULA prefixes used in the intruder configures ACP connect but none of the actual /64
   (Manual Addressing Sub-Scheme), /127 (ACP Zone Addressing Sub-
   Scheme), /112 or /120 (Vlong Addressing Sub-Scheme) routes of actual
   ACP nodes.  If ACP interfaces are configured with non ULA prefixes,
   then those prefixes cannot be aggregated without further configured
   policy on it.
   The full workflow including the mechanism by which a registrar would
   select which node ACP edge node.  This explains the above recommendation
   to give such use ACP ULA prefix covered prefixes for ACP connect interfaces:
   They allow for a certificate shorter list of prefixes to is subject be signaled via RFC4191
   to future
   work.

8.1.2.  Software Components NMS hosts and software components.

   The ACP connect mechanism be only be used to connect physically
   external systems (NMS hosts) to the edge nodes that have a Vlong ACP but also other applications,
   containers address MAY allocate a
   subset of their /112 or virtual machines.  In fact, one possible way /120 address prefix to ACP connect
   interface(s) to eliminate the security issue of need to non-autonomically configure/
   provision the external address prefixes for such ACP connect interface is
   to collocate an interfaces.

8.1.4.  Combined ACP/Data-Plane Interface (VRF Select)

                        Combined ACP edge node and an Data-Plane interface
                                                .
     +--------+       +--------------------+    .   +--------------+
     | ACP    |       |ACP Edge No         |    .   | NMS host by making one a virtual
   machine or container inside the other; Host(s)  |
     | Node   |       |                    |    .   | / Software   |
     |        |       |  [ACP  ].          |    .   |              |+
     |        |       | .[VRF  ] .[VRF   ] |    v   | "ACP address"||
     |        +-------+.         .[Select].+--------+ "Date Plane  ||
     |        |   ^   | .[Data ].          |        |  Address(es)"||
     |        |   .   |  [Plane]           |        |              ||
     |        |   .   |  [     ]           |        +--------------+|
     +--------+   .   +--------------------+         +--------------+
                  .
           Data-Plane "native" and therefore converting the
   unprotected external + ACP subnet into an internal auto-negotiated/encrypted

                           Figure 14: VRF select

   Using two physical and/or virtual subnet in subnets (and therefore interfaces)
   into NMS Hosts (as per Section 8.1.1) or Software (as per
   Section 8.1.2) may be seen as additional complexity, for example with
   legacy NMS Hosts that support only one IP interface.

   To provide a single device.  This would ultimately result in a fully subnet into both ACP enabled
   NMS host with minimum impact to and Data-Plane, the ACP Edge
   node needs to de-multiplex packets from NMS hosts software architecture. into ACP VRF and
   Data-Plane.  This approach is not limited to NMS hosts but could equally be
   applied to devices consisting of one or more VNF (virtual network
   functions): An internal virtual subnet connecting out-of-band-
   management interfaces of sometimes called "VRF select".  If the ACP VRF
   has no overlapping IPv6 addresses with the Data-Plane (as it should),
   then this function can use the VNFs to an ACP edge router VNF. IPv6 Destination address.  The core requirement problem
   is that Source Address Selection on the software components need to have a
   network stack that permits access NMS Host(s) according to RFC6724.

   Consider the simple case: The ACP and optionally also the
   data-plane.  Like in uses only one ULA prefix, the physical setup ACP
   IPv6 prefix for NMS hosts this can be
   realized via two internal virtual subnets.  One that is connecting to the Combined ACP (which could be a container or virtual machine and Data-Plane interface is covered
   by itself), that ULA prefix.  The ACP edge node announces both the ACP IPv6
   prefix and one (or more) connecting into prefixes for the data-plane.

   This "internal" use of Data-Plane.  Without
   further policy configurations on the NMS Host(s), it may select its
   ACP connect approach should not considered to
   be address as a "workaround" source address for Data-Plane ULA destinations
   because in this case it is possible to build a
   correct security model: It is not necessary to rely of Rule 8 of RFC6724.  The ACP edge node can pass on unprovable
   external physical security mechanisms as in the case of external NMS
   hosts.  Instead,
   packet to the orchestration of Data-Plane, but the ACP, ACP source address should not be
   used for Data-Plane traffic, and return traffic may fail.

   If the virtual ACP carries multiple ULA prefixes or non-ULA ACP connect
   prefixes, then the correct source address selection becomes even more
   problematic.

   With separate ACP connect and Data-Plane subnets and the software components can be done by trusted software RFC4191 prefix
   announcements that
   could be considered are to be part of routed across the ANI (or even an extended ACP).
   This software component is responsible to ensure that only trusted
   software components ACP connect interface,
   RFC6724 source address selection Rule 5 (use address of outgoing
   interface) will get access to that virtual subnet and be used, so that
   only above problems do not occur, even in
   more trusted software components will get access to both complex cases of multiple ULA and non-ULA prefixes in the ACP virtual subnet
   routing table.

   To achieve the same behavior with a Combined ACP and Data-Plane
   interface, the data-plane (because those ACP users
   could leak traffic between Edge Node needs to behave as two separate routers
   on the interface: One link-local IPv6 address/router for its ACP
   reachability, and data-plane).  This trust could be
   established one link-local IPv6 address/router for example through cryptographic means such signed
   software packages. its Data-
   Plane reachability.  The specification of these mechanisms is subject
   to future work.

   Note that ASA (Autonomic Software Agents) could also be software
   components as described in this section, but further details of ASAs Router Advertisements for both are subject to future work.

8.1.3.  Auto Configuration

   ACP edge nodes, NMS hosts and software components that as
   described
   in above (Section 8.1.3): For the previous section are meant to be composed via virtual
   interfaces SHOULD support on ACP, the ACP prefix is
   announced together with RFC4191 option for the prefixes routed across
   the ACP connect subnet Stateless Address
   Autoconfiguration (SLAAC - [RFC4862]) and route autoconfiguration
   according lifetime=0 to [RFC4191].

   The ACP edge node acts disqualify this next-hop as a default
   router.  For the Data-Plane, the Data-Plane prefix(es) are announced
   together with whatever dafault router parameters are used for the
   Data-Plane.

   In result, RFC6724 source address selection Rule 5.5 may result in
   the same correct source address selection behavior of NMS hosts
   without further configuration on it as the separate ACP connect subnet,
   providing and
   Data-Plane interfaces.  As described in the (auto-)configured prefix text for the ACP connect subnet Rule 5.5, this
   is only a may, because IPv6 hosts are not required to track next-hop
   information.  If an NMS hosts and/or software components.  The Host does not do this, then separate ACP edge node uses route
   prefix option
   connect and Data-Plane interfaces are the preferable method of RFC4191
   attachment.  Hosts implementing [RFC8028] should (instead of may)
   implement [RFC6724] Rule 5.5, so it is preferred for hosts to announce support
   [RFC8028].

   ACP edge nodes MAY support the default route (::/) with a
   lifetime Combined ACP and Data-Plane interface.

8.1.5.  Use of 0 GRASP

   GRASP can and aggregated prefixes for routes in the should be possible to use across ACP routing
   table with normal lifetimes.  This will ensure that connect
   interfaces, especially in the ACP edge node
   does not become architectural correct solution when it
   is used as a default router, but that the mechanism to connect Software (e.g., ASA or legacy NMS hosts and software
   components will route
   applications) to the prefixes used in ACP.  Given how the ACP to is the ACP edge
   node.

   Aggregated prefix means that security and
   transport substrate for GRASP, the ACP edge node needs trustworthiness of nodes/software
   allowed to only announce
   the /48 ULA prefixes used participate in the ACP but none GRASP domain is one of the actual /64
   (Manual Addressing Sub-Scheme), /127 (ACP Zone Addressing Sub-
   Scheme), /112 or /120 (Vlong Addressing Sub-Scheme) routes of actual main
   reasons why the ACP nodes.  If section describes no solution with non-ACP
   routers participating in the ACP routing table.

   ACP connect interfaces are configured with non ULA prefixes,
   then those prefixes cannot can be aggregated without further configured
   policy on dealt with in the GRASP ACP edge node.  This explains the above recommendation
   to use domain like
   any other ACP ULA prefix covered prefixes for interface assuming that any physical ACP connect interfaces:
   They allow for a shorter list of prefixes to be signaled via RFC4191
   to NMS hosts
   interface is physically protected from attacks and software components.

   The that the connected
   Software or NMS Hosts are equally trusted as that on other ACP nodes.
   ACP edge nodes that SHOULD have a Vlong ACP address MAY allocate a
   subset of their /112 or /120 address prefix to ACP connect
   interface(s) to eliminate the need options to non-autonomically configure/
   provision the address prefixes for such ACP connect interfaces.

8.1.4.  Combined ACP/Data-Plane Interface (VRF Select)

                        Combined ACP filter GRASP messages in and Data-Plane interface
                                                .
     +--------+       +--------------------+    .   +--------------+
     |
   out of ACP    |       |ACP Edge No         |    .   | NMS Host(s)  |
     | Node   |       |                    |    .   | / Software   |
     |        |       |  [ACP  ].          |    .   |              |+
     |        |       | .[VRF  ] .[VRF   ] |    v   | "ACP address"||
     |        +-------+.         .[Select].+--------+ "Date Plane  ||
     |        |   ^   | .[Data ].          |        |  Address(es)"||
     |        |   .   |  [Plane]           |        |              ||
     |        |   .   |  [VRF  ]           |        +--------------+|
     +--------+   .   +--------------------+         +--------------+
                  .
           data-plane "native" connect interfaces (permit/deny) and + ACP auto-negotiated/encrypted

                           Figure 9: VRF select

   Using two physical and/or virtual subnets (and therefore interfaces)
   into NMS Hosts (as per Section 8.1.1) MAY have more fine-
   grained filtering (e.g., based on IPv6 address of originator or Software (as per
   Section 8.1.2) may
   objective).

   When using "Combined ACP and Data-Plane Interfaces", care must be seen as additional complexity, for example with
   legacy NMS Hosts
   taken that support only one IP interface.

   To provide a single subnet into both ACP and data-plane, GRASP messages intended for the ACP Edge
   node needs to de-multiplex packets GRASP domain
   received from Software or NMS hosts into Hosts are forwarded by ACP VRF and
   data-plane VRF.  This edge nodes.
   Currently there is sometimes called "VRF select".  If no definition for a GRASP security and transport
   substrate beside the ACP
   VRF has ACP, so there is no overlapping IPv6 addresses with definition how such
   Software/NMS Host could participate in two separate GRASP Domains
   across the data-plane (as same subnet (ACP and Data-Plane domains).  At current it
   should), then this function can use the IPv6 Destination address.
   The problem
   is Source Address Selection assumed that all GRASP packets on the NMS Host(s) according a Combined ACP and Data-Plane
   interface belong to RFC6724.

   Consider the simple case: The GRASP ACP uses only one ULA prefix, Domain.  They must all use the ACP
   IPv6 prefix for addresses of the Combined ACP and data-plane interface is covered
   by that ULA prefix. Software/NMS Hosts.  The ACP edge node announces both the ACP link-local IPv6
   prefix and one (or more) prefixes
   addresses of Software/NMS Hosts (used for GRASP M_DISCOVERY and
   M_FLOOD messages) are also assumed to belong to the data-plane.  Without
   further policy configurations on the NMS Host(s), it may select its ACP address as a source address for data-plane ULA destinations
   because of Rule 8 of RFC6724.  The
   space.

8.2.  ACP edge node can pass on through Non-ACP L3 Clouds (Remote ACP neighbors)

   Not all nodes in a network may support the
   packet to ACP.  If non-ACP Layer-2
   devices are between ACP nodes, the data-plane, but ACP will work across it since it
   is IP based.  However, the autonomic discovery of ACP source address should neighbors via
   DULL GRASP is only intended to work across L2 connections, so it is
   not be
   used for data-plane traffic, and return traffic may fail.

   If sufficient to autonomically create ACP connections across non-ACP
   Layer-3 devices.

8.2.1.  Configured Remote ACP neighbor

   On the ACP carries multiple ULA prefixes or non-ULA node, remote ACP connect
   prefixes, then neighbors are configured explicitly.  The
   parameters of such a "connection" are described in the correct source following
   ABNF.  Future work could transform this into a YANG ([RFC7950]) data
   model.

     connection = [ method , local-addr, remote-addr, ?pmtu ]
     method   = [ "IKEv2" , ?port ]
     method //= [ "DTLS",    port ]
     local-addr  = [ address selection becomes even more
   problematic.

   With separate , ?vrf  ]
     remote-addr = [ address ]
     address = ("any" | ipv4-address | ipv6-address )
     vrf = tstr ; Name of a VRF on this node with local-address

     ABNF for parameters of explicitly configured remote ACP connect neighbors

   Explicit configuration of a remote-peer according to this ABNF
   provides all the information to build a secure channel without
   requiring a tunnel to that peer and data-plane subnets running DULL GRASP inside of it.

   The configuration includes the parameters otherwise signaled via DULL
   GRASP: local address, remote (peer) locator and method.  The
   differences over DULL GRASP local neighbor discovery and secure
   channel creation are as follows:

   o  The local and remote address can be IPv4 or IPv6 and RFC4191 prefix
   announcements that are typically
      global scope addresses.

   o  The vrf across which the connection is built (and in which local-
      addr exists) can to be routed specified.  If vrf is not specified, it is
      the default vrf on the node.  In DULL GRASP the VRF is implied by
      the interface across which DULL GRASP operates.

   o  If local address is "any", the ACP connect interface,
   RFC6724 local address used when initiating
      a secure channel connection is decided by source address selection Rule 5 (use address of outgoing
   interface) will be used, so that above problems do not occur, even in
   more complex cases
      ([RFC6724] for IPv6).  As a responder, the connection listens on
      all addresses of multiple ULA and non-ULA prefixes the node in the ACP
   routing table.

   To achieve selected vrf.

   o  Configuration of port is only required for methods where no
      defaults exist (e.g., "DTLS").

   o  If remote address is "any", the same behavior with connection is only a Combined ACP and data-plane
   interface, the ACP Edge Node needs responder.
      It is a "hub" that can be used by multiple remote peers to behave as two separate routers
   on the interface: One link-local IPv6 address/router for its ACP
   reachability, and one link-local IPv6 address/router for its data-
   plane reachability.  The Router Advertisements connect
      simultaneously - without having to know or configure their
      addresses.  Example: Hub site for both are as
   described above (Section 8.1.3): For remote "spoke" sites reachable
      over the ACP, Internet.

   o  Pmtu should be configurable to overcome issues/limitations of Path
      MTU Discovery (PMTUD).

   o  IKEv2/IPsec to remote peers should support the optional NAT
      Traversal (NAT-T) procedures.

8.2.2.  Tunneled Remote ACP prefix Neighbor

   An IPinIP, GRE or other form of pre-existing tunnel is
   announced together with RFC4191 option for the prefixes routed across
   the configured
   between two remote ACP peers and lifetime=0 to disqualify this next-hop as a default
   router.  For the data-plane, virtual interfaces representing
   the data-plane prefix(es) are announced
   together with whatever dafault router parameters tunnel are used for the
   data-plane. configured to "ACP enable".  This will enable IPv6
   link local addresses and DULL on this tunnel.  In result, RFC6724 source address selection Rule 5.5 may result in
   the same correct source address selection behavior of NMS hosts
   without further configuration on it as the separate tunnel
   is used for normal "L2 adjacent" candidate ACP connect neighbor discovery
   with DULL and
   data-plane interfaces.  As secure channel setup procedures described in the text for Rule 5.5, this
   is only a may, because IPv6 hosts are not required to track next-hop
   information.  If an NMS Host does not do this, then separate
   document.

   Tunneled Remote ACP
   connect Neighbor requires two encapsulations: the
   configured tunnel and data-plane interfaces are the preferable method secure channel inside of
   attachment.  Hosts implementing [RFC8028] should (instead that tunnel.  This
   makes it in general less desirable than Configured Remote ACP
   Neighbor.  Benefits of may)
   implement [RFC6724] Rule 5.5, so tunnels are that it may be easier to implement
   because there is preferred for hosts no change to support
   [RFC8028]. the ACP edge nodes MAY support functionality - just running it
   over a virtual (tunnel) interface instead of only native interfaces.
   The tunnel itself may also provide PMTUD while the Combined secure channel
   method may not.  Or the tunnel mechanism is permitted/possible
   through some firewall while the secure channel method may not.

8.2.3.  Summary

   Configured/Tunneled Remote ACP neighbors are less "indestructible"
   than L2 adjacent ACP and neighbors based on link local addressing, since
   they depend on more correct Data-Plane interface.

8.1.5.  Use of GRASP

   GRASP can operations, such as routing
   and should global addressing.

   Nevertheless, these options may be possible crucial to use across ACP connect
   interfaces, especially in incrementally deploy
   the architectural correct solution when ACP, especially if it is used as a mechanism meant to connect Software (e.g.: ASA or legacy NMS
   applications) to the ACP.  Given how islands across the
   Internet.  Implementations SHOULD support at least Tunneled Remote
   ACP Neighbors via GRE tunnels - which is likely the security and
   transport substrate for GRASP, most common
   router-to-router tunneling protocol in use today.

   Future work could envisage an option where the trustworthiness edge nodes of nodes/software
   allowed the L3
   cloud is configured to automatically forward ACP discovery messages
   to participate in the right exit point.  This optimization is not considered in this
   document.

9.  Benefits (Informative)

9.1.  Self-Healing Properties

   The ACP GRASP domain is one of the main
   reasons why self-healing:

   o  New neighbors will automatically join the ACP section describes no solution with non-ACP
   routers participating after successful
      validation and will become reachable using their unique ULA
      address across the ACP.

   o  When any changes happen in the ACP topology, the routing table.

   ACP connect interfaces can be dealt with protocol used
      in the GRASP ACP will automatically adapt to the changes and will
      continue to provide reachability to all nodes.

   o  If the domain like
   any other certificate of an existing ACP interface assuming that any physical node gets revoked, it
      will automatically be denied access to the ACP connect
   interface as its domain
      certificate will be validated against a Certificate Revocation
      List during authentication.  Since the revocation check is physically protected from attacks and that only
      done at the connected
   Software or NMS Hosts establishment of a new security association, existing
      ones are equally trusted as that on other ACP nodes.
   ACP edge nodes SHOULD have options not automatically torn down.  If an immediate disconnect
      is required, existing sessions to filter GRASP messages in and
   out of a freshly revoked node can be
      re-set.

   The ACP connect interfaces (permit/deny) can also sustain network partitions and MAY have more fine-
   grained filtering (e.g.: based on IPv6 address of originator or
   objective).

   When mergers.  Practically
   all ACP operations are link local, where a network partition has no
   impact.  Nodes authenticate each other using "Combined the domain certificates
   to establish the ACP locally.  Addressing inside the ACP remains
   unchanged, and Data-Plane Interfaces", care must be
   taken that only GRASP messages intended for the routing protocol inside both parts of the ACP GRASP domain
   received from Software or NMS Hosts will
   lead to two working (although partitioned) ACPs.

   There are forwarded by ACP edge nodes.
   Currently there is no definition for few central dependencies: A certificate revocation list
   (CRL) may not be available during a GRASP security and transport
   substrate beside the ACP, so there is network partition; a suitable
   policy to not immediately disconnect neighbors when no definition how such
   Software/NMS Host could participate in two separate GRASP Domains
   across the same subnet (ACP and data-plane domains).  At current it CRL is assumed
   available can address this issue.  Also, an ACP registrar or
   Certificate Authority might not be available during a partition.
   This may delay renewal of certificates that all GRASP packets on a Combined ACP and data-plane
   interface belong are to expire in the GRASP ACP Domain.  They must all use
   future, and it may prevent the ACP
   IPv6 addresses enrollment of new nodes during the Software/NMS Hosts.  The link-local IPv6
   addresses
   partition.

   Highly resilient ACP designs can be built by using ACP registrars
   with embedded sub-CA, as outlined in Section 10.3.4.  As long a a
   partition is left with one or more of Software/NMS Hosts (used for GRASP M_DISCOVERY and
   M_FLOOD messages) are also assumed to belong such ACP registrars, it can
   continue to enroll new candidate ACP nodes as long as the ACP address
   space.

8.2.
   registrars sub-CA certificate does not expire.  Because the ACP through Non-ACP L3 Clouds (Remote
   addressing relies on unique Registrar-IDs, a later re-merge of
   partitions will also not cause problems with ACP neighbors)

   Not addresses assigned
   during partitioning.

   After a network partition, a re-merge will just establish the
   previous status, certificates can be renewed, the CRL is available,
   and new nodes can be enrolled everywhere.  Since all nodes in use the
   same trust anchor, a network may support re-merge will be smooth.

   Merging two networks with different trust anchors requires the ACP.  If non-ACP Layer-2
   devices trust
   anchors to mutually trust each other (for example, by cross-signing).
   As long as the domain names are between ACP nodes, different, the ACP addressing will work across not
   overlap (see Section 6.10).

   It is also highly desirable for implementation of the ACP to be able
   to run it since over interfaces that are administratively down.  If this is
   not feasible, then it might instead be possible to request explicit
   operator override upon administrative actions that would
   administratively bring down an interface across which the ACP is IP based.  However,
   running.  Especially if bringing down the autonomic discovery of ACP neighbors via
   DULL GRASP is only intended known to work disconnect
   the operator from the node.  For example any such down administrative
   action could perform a dependency check to see if the transport
   connection across L2 connections, which this action is performed is affected by the
   down action (with default RPL routing used, packet forwarding will be
   symmetric, so it this is
   not sufficient actually possible to autonomically create check).

9.2.  Self-Protection Properties

9.2.1.  From the outside

   As explained in Section 6, the ACP connections across non-ACP
   Layer-3 devices.

8.2.1.  Configured Remote is based on secure channels built
   between nodes that have mutually authenticated each other with their
   domain certificates.  The channels themselves are protected using
   standard encryption technologies like DTLS or IPsec which provide
   additional authentication during channel establishment, data
   integrity and data confidentiality protection of data inside the ACP neighbor

   On
   and in addition, provide replay protection.

   An attacker will not be able to join the ACP node, remote unless having a valid
   domain certificate, also packet injection and sniffing traffic will
   not be possible due to the security provided by the encryption
   protocol.

   The ACP neighbors are configured also serves as follows.
   Future work could transform this into a YANG ([RFC7950]) data model.

     connection = [ method , local-addr, remote-addr, ?pmtu ]
     method   = [ "IKEv2" , ?port ]
     method //= [ "dTLS",    port ]
     local-addr  = [ address , ?vrf  ]
     remote-addr = [ address ]
     address = ("any" | ipv4-address | ipv6-address )
     vrf = tstr ; Name protection (through authentication and
   encryption) for protocols relevant to OAM that may not have secured
   protocol stack options or where implementation or deployment of a VRF those
   options fails on this node with local-address

   Explicit configuration of a remote-peer provides all the information some vendor/product/customer limitations.  This
   includes protocols such as SNMP, NTP/PTP, DNS, DHCP, syslog,
   Radius/Diameter/TACACS, IPFIX/Netflow - just to build name a few.
   Protection via the ACP secure channel without requiring a tunnel hop-by-hop channels for these protocols
   is meant to that peer and
   running DULL GRASP inside of it. be only a stopgap though: The configuration includes the parameters otherwise signaled via DULL
   GRASP: local address, remote (peer) locator ultimate goal is for these
   and method.  The
   differences over DULL GRASP local neighbor discovery other protocols to use end-to-end encryption utilizing the domain
   certificate and rely on the ACP secure
   channel creation are as follows:

   o channels primarily for zero-
   touch reliable connectivity, but not primarily for security.

   The local and remote address can remaining attack vector would be IPv4 to attack the underlying ACP
   protocols themselves, either via directed attacks or by denial-of-
   service attacks.  However, as the ACP is built using link-local IPv6 and
   address, remote attacks are typically
      global scope addresses.

   o impossible.  The vrf across which ULA addresses are only
   reachable inside the connection is built (and in which local-
      addr exists) can ACP context, therefore, unreachable from the
   Data-Plane.  Also, the ACP protocols should be implemented to be specified.  If vrf is
   attack resistant and not specified, it is consume unnecessary resources even while
   under attack.

9.2.2.  From the default vrf inside

   The security model of the ACP is based on trusting all members of the node.  In DULL GRASP
   group of nodes that do receive an ACP domain certificate for the VRF is implied same
   domain.  Attacks from the inside by a compromised group member are
   therefore the interface across which DULL GRASP operates.

   o  If local address biggest challenge.

   Group members must be protected against attackers so that there is "any", the local address used when initiating no
   easy way to compromise them, or use them as a secure channel connection is decided by source address selection
      ([RFC6724] proxy for IPv6).  As a responder, attacking
   other devices across the connection listens on
      all addresses of ACP.  For example, management plane
   functions (transport ports) should only be reachable from the node in ACP but
   not the selected vrf.

   o  Configuration of port is only required Data-Plane.  Especially for methods where those management plane functions
   that have no
      defaults exist (e.g.: "dTLS").

   o  If remote address good protection by themselves because they do not have
   secure end-to-end transport and to whom ACP does not only provides
   automatic reliable connectivity but also protection against attacks.
   Protection across all potential attack vectors is "any", typically easier to
   do in devices whose software is designed from the connection ground up with
   security in mind than with legacy software based systems where the
   ACP is only a responder.
      It added on as another feature.

   As explained above, traffic across the ACP SHOULD still be end-to-end
   encrypted whenever possible.  This includes traffic such as GRASP,
   EST and BRSKI inside the ACP.  This minimizes man in the middle
   attacks by compromised ACP group members.  Such attackers cannot
   eavesdrop or modify communications, they can just filter them (which
   is a "hub" that unavoidable by any means).

   Further security can be used achieved by multiple remote peers to connect
      simultaneously - without having to know or configure their
      addresses.  Example: Hub site for remote "spoke" sites reachable
      over constraining communication
   patterns inside the Internet.

   o  Pmtu should ACP, for example through roles that could be configurable to overcome issues/limitations of
      PMTUD (Path MTU Discovery).

   o  IKEv2/IPsec to remote peers should support
   encoded into the optional NAT-T
      procedures (NAT Traversal).

8.2.2.  Tunneled Remote ACP Neighbor

   An IPinIP, GRE or other form of pre-existing tunnel domain certificates.  This is configured
   between two remote subject for future
   work.

9.3.  The Administrator View

   An ACP peers is self-forming, self-managing and self-protecting, therefore
   has minimal dependencies on the virtual interfaces representing administrator of the tunnel are configured network.
   Specifically, since it is independent of configuration, there is no
   scope for configuration errors on the ACP itself.  The administrator
   may have the option to "ACP enable".  This will enable IPv6
   link local addresses and DULL on this tunnel.  In result, or disable the tunnel entire approach, but
   detailed configuration is used for normal "L2 adjacent" candidate not possible.  This means that the ACP neighbor discovery
   with DULL and secure channel setup procedures described must
   not be reflected in this
   document.

   Tunneled Remote ACP Neighbor requires two encapsulations: the
   configured tunnel running configuration of nodes, except a
   possible on/off switch.

   While configuration is not possible, an administrator must have full
   visibility of the ACP and all its parameters, to be able to do
   trouble-shooting.  Therefore, an ACP must support all show and debug
   options, as for any other network function.  Specifically, a network
   management system or controller must be able to discover the secure channel inside of that tunnel. ACP, and
   monitor its health.  This
   makes it in general less desirable than Configured Remote ACP
   Neighbor.  Benefits visibility of tunnels are that it may ACP operations must clearly
   be easier separated from visibility of Data-Plane so automated systems will
   never have to implement
   because there is no change deal with ACP aspect unless they explicitly desire to the
   do so.

   Since an ACP functionality - just running it
   over is self-protecting, a virtual (tunnel) interface instead of only native interfaces.
   The tunnel itself may also provide PMTUD while node not supporting the secure channel
   method may not.  Or ACP, or
   without a valid domain certificate cannot connect to it.  This means
   that by default a traditional controller or network management system
   cannot connect to an ACP.  See Section 8.1.1 for more details on how
   to connect an NMS host into the tunnel mechanism is permitted/possible
   through some firewall while ACP.

10.  Further Considerations (Informative)

   The following sections cover topics that are beyond the primary scope
   of this document (e.g., bootstrap), that explain decisions made in
   this document (e.g.: choice of GRASP) or that explain desirable
   extensions or implementation details for the secure channel method may not.

8.2.3.  Summary

   Configured/Tunneled Remote ACP neighbors that are less "indestructible"
   than L2 adjacent ACP neighbors based on link local addressing, since
   they depend on more correct data-plane operations, such as routing not
   considered to be appropriate to standardize in this document.

10.1.  BRSKI Bootstrap (ANI)

   [I-D.ietf-anima-bootstrapping-keyinfra] (BRSKI) describes how nodes
   with an IDevID certificate can securely and global addressing.

   Nevertheless, these options may be crucial zero-touch enroll with a
   domain certificate (LDevID) to incrementally deploy support the ACP, especially if it is meant to connect islands across ACP.  BRSKI also leverages
   the
   Internet.  Implementations SHOULD support at least Tunneled Remote ACP Neighbors via GRE tunnels - which is likely to enable zero-touch bootstrap of new nodes across networks
   without any configuration requirements across the most common
   router-to-router tunneling protocol transit nodes
   (e.g., no DHCP/DNS forwarding/server setup).  This includes otherwise
   not configured networks as described in use today.

   Future work could envisage Section 3.2.  Therefore BRSKI
   in conjunction with ACP provides for a secure and zero-touch
   management solution for complete networks.  Nodes supporting such an option where the edge
   infrastructure (BRSKI and ACP) are called ANI nodes (Autonomic
   Networking Infrastructure), see [I-D.ietf-anima-reference-model].
   Nodes that do not support an IDevID but only an (insecure) vendor
   specific Unique Device Identifier (UDI) or nodes whose manufacturer
   does not support a MASA could use some future security reduced
   version of the L3
   cloud BRSKI.

   When BRSKI is configured used to automatically forward provision a domain certificate (which is called
   enrollment), the BRSKI registrar (acting as an enhanced EST server)
   must include the subjectAltName / rfc822Name encoded ACP discovery messages address and
   domain name to the right exit point.  This optimisation enrolling node (called pledge) via its response to
   the pledges EST CSR Attribute request that is not considered mandatory in this
   document.

9.  Benefits (Informative)

9.1.  Self-Healing Properties BRSKI.

   The Certificate Authority in an ACP is self-healing:

   o  New neighbors will automatically join network must not change the
   subjectAltName / rfc822Name in the certificate.  The ACP after successful
      validation and will become reachable using nodes can
   therefore find their unique ULA ACP address across the ACP.

   o  When any changes happen and domain using this field in the topology, the routing protocol used
   domain certificate, both for themselves, as well as for other nodes.

   The use of BRSKI in conjunction with the ACP will automatically adapt can also help to the changes further
   simplify maintenance and will
      continue renewal of domain certificates.  Instead of
   relying on CRL, the lifetime of certificates can be made extremely
   small, for example in the order of hours.  When a node fails to provide reachability
   connect to all nodes.

   o  If the domain certificate of an existing ACP node gets revoked, within its certificate lifetime, it
      will automatically be denied access cannot connect
   to the ACP as to renew its domain certificate will be validated against a Certificate Revocation
      List during authentication.  Since across it (using just EST), but
   it can still renew its certificate as an "enrolled/expired pledge"
   via the revocation check is BRSKI bootstrap proxy.  This requires only
      done at the establishment of a new security association, existing
      ones are not automatically torn down.  If an immediate disconnect
      is required, existing sessions to a freshly revoked node can be
      re-set.

   The ACP can also sustain network partitions and mergers.  Practically
   all ACP operations are link local, where a network partition has no
   impact.  Nodes authenticate each other using that the BRSKI
   registrar honors expired domain certificates
   to establish the ACP locally.  Addressing inside the ACP remains
   unchanged, and that the routing protocol inside both parts of the ACP will
   lead pledge
   first attempts to two working (although partitioned) ACPs.

   There are few central dependencies: A perform TLS authentication for BRSKI bootstrap with
   its expired domain certificate revocation list
   (CRL) may not be available during a network partition; a suitable
   policy - and only reverts to not immediately disconnect neighbors its IDevID when no CRL is
   available can address
   this issue.  Also, a fails.  This mechanism could also render CRLs unnecessary
   because the BRSKI registrar or Certificate
   Authority might in conjunction with the CA would not be available during
   renew revoked certificates - only a partition.  This may delay
   renewal "Do-not-renew" list would be
   necessary on BRSKI registrars/CA.

   In the absence of BRSKI or less secure variants thereof, provisioning
   of certificates that are to expire in the future, and it may
   prevent the enrolment involve one or more touches or non-standardized
   automation.  Node vendors usually support provisioning of new nodes during the partition.

   After a network partition, a re-merge will just establish the
   previous status,
   certificates can be renewed, the CRL is available, into nodes via PKCS#7 (see [RFC2315]) and new may support
   this provisioning through vendor specific models via Netconf
   ([RFC6241]).  If such nodes also support Netconf Zero-Touch
   ([I-D.ietf-netconf-zerotouch]) then this can be enrolled everywhere.  Since all nodes use the
   same trust anchor, a re-merge will be smooth.

   Merging two networks with different trust anchors requires the trust
   anchors combined to mutually trust each other (for example, by cross-signing).
   As long as the zero-
   touch provisioning of domain names certificates into nodes.  Unless there
   are different, the addressing will not
   overlap (see Section 6.10).

   It is also highly desirable for implementation equivalent integration of Netconf connections across the ACP to be able
   to run it over interfaces that are administratively down.  If this as
   there is
   not feasible, then it might instead be possible to request explicit
   operator override upon administrative actions that in BRSKI, this combination would
   administratively bring down an interface not support zero-touch
   bootstrap across which the a not configured network though.

10.2.  ACP is
   running.  Especially if bringing down the (and BRSKI) Diagnostics

   Even though ACP and ANI in general are taking out many manual
   configuration mistakes through their automation, it is known important to disconnect
   the operator from
   provide good diagnostics for them.

   The basic diagnostics is support of (yang) data models representing
   the node.  For example any such down administrative
   action could perform a dependency check to see if complete (auto-)configuration and operational state of all
   components: BRSKI, GRASP, ACP and the transport
   connection across which this action is performed is affected infrastructure used by the
   down action (with default RPL routing used, packet forwarding will be
   symmetric, them:
   TLS/DTLS, IPsec, certificates, trust anchors, time, VRF and so on.
   While necessary, this is actually possible to check).

9.2.  Self-Protection Properties

9.2.1.  From not sufficient:

   Simply representing the outside

   As explained in Section 6, state of components does not allow operators
   to quickly take action - unless they do understand how to interpret
   the ACP is based on secure channels built
   between nodes that have mutually authenticated each other with their
   domain certificates.  The channels themselves are protected using
   standard encryption technologies like DTLS or IPsec which provide
   additional authentication during channel establishment, data
   integrity data, and data confidentiality protection that can mean a requirement for deep understanding of data inside
   all components and how they interact in the ACP/ANI.

   Diagnostic supports should help to quickly answer the ACP
   and in addition, provide replay protection.

   An attacker will not be able questions
   operators are expected to join ask, such as "is the ACP unless having working
   correctly?", or "why is there no ACP connection to a valid
   domain certificate, also packet injection and sniffing traffic will known
   neighboring node?"

   In current network management approaches, the logic to answer these
   questions is most often built as centralized diagnostics software
   that leverages the above mentioned data models.  While this approach
   is feasible for components utilizing the ANI, it is not be possible due sufficient to
   diagnose the security provided by ANI itself:

   o  Developing the encryption
   protocol.

   The ACP also serves logic to identify common issues requires
      operational experience with the components of the ANI.  Letting
      each management system define its own analysis is inefficient.  As
      much as protection (through authentication and
   encryption) for protocols relevant possible, future work should attempt to OAM standardize data
      models that support common error diagnostic.

   o  When the ANI is not operating correctly, it may not have secured
   protocol stack options or where implementation or deployment be possible to
      run diagnostics from remote because of those
   options fails missing connectivity.  The
      ANI should therefore have diagnostic capabilities available
      locally on some vendor/product/customer limitations.  This
   includes protocols the nodes themselves.

   o  Certain operations are difficult or impossible to monitor in real-
      time, such as SNMP, NTP/PTP, DNS, DHCP, syslog,
   Radius/Diameter/TACACS, IPFIX/Netflow - just to name initial bootstrap issues in a few.
   Protection via the ACP secure hop-by-hop channels network location where
      no capabilities exist to attach local diagnostics.  Therefore it
      is important to also define means of capturing (logging)
      diagnostics locally for later retrieval.  Ideally, these protocols
   is meant captures
      are also non-volatile so that they can survive extended power-off
      conditions - for example when a device that fails to be only brought up
      zero-touch is being sent back for diagnostics at a stopgap though: more
      appropriate location.

   The ultimate goal most simple form of diagnostics answering questions like the
   above is for these
   and other protocols to use end-to-end encryption utilizing represent the domain
   certificate and rely on relevant information sequentially in
   dependency order, so that the first non-expected/non-operational item
   is the most likely root cause.  Or just log/highlight that item.  For
   example:

   Q: Is ACP secure channels primarily for zero-
   touch reliable connectivity, but not primarily for security.

   The remaining attack vector would be operational to attack accept neighbor connections:

   o  Check if any potentially necessary configuration to make ACP/ANI
      operational are correct (see Section 10.5 for a discussion of such
      commands).

   o  Does the underlying AN
   protocols themselves, either via directed attacks system time look reasonable, or by denial-of-
   service attacks.  However, as could it be the default
      system time after clock chip battery failure (certificate checks
      depend on reasonable notion of time).

   o  Does the node have keying material - domain certificate, trust
      anchors.

   o  If no keying material and ANI is supported/enabled, check the
      state of BRSKI (not detailed in this example).

   o  Check the validity of the domain certificate:

      *  Does the certificate authenticate against the trust anchor?

      *  Has it been revoked?

      *  Was the last scheduled attempt to retrieve a CRL successful
         (e.g., do we know that our CRL information is up to date).

      *  Is the ACP is built using link-local IPv6
   address, remote attacks are impossible.  The ULA addresses are only
   reachable inside certificate valid: validity start time in the past,
         expiration time in the future?

      *  Does the certificate have a correctly formatted ACP context, therefore, unreachable from information
         field?

   o  Was the
   data-plane.  Also, ACP VRF successfully created?

   o  Is ACP enabled on one or more interfaces that are up and running?

   If all this looks good, the ACP protocols should be implemented to be
   attack resistant and running locally "fine" -
   but we did not consume unnecessary resources even while
   under attack.

9.2.2.  From the inside

   The security model of check any ACP neighbor relationships.

   Question: why does the node not create a working ACP is based connection to a
   neighbor on trusting all members of an interface?

   o  Is the
   group of nodes that do receive interface physically up?  Does it have an ACP domain certificate IPv6 link-local
      address?

   o  Is it enabled for ACP?

   o  Do we successfully send DULL GRASP messages to the same
   domain.  Attacks from interface (link
      layer errors)?

   o  Do we receive DULL GRASP messages on the inside by a compromised group member are
   therefore interface?  If not, some
      intervening L2 equipment performing bad MLD snooping could have
      caused problems.  Provide e.g., diagnostics of the biggest challenge.

   Group members must overall MLD querier
      IPv6 and MAC address.

   o  Do we see the secured so that there are no easy way
   to compromise them, such as data-plane accessible privilege level
   with simple passwords.  This is a lot easier to do ACP objective in devices whose
   software is designed any DULL GRASP message from that
      interface?  Diagnose the ground up with security in mind than supported secure channel methods.

   o  Do we know the MAC address of the neighbor with legacy software based system where ACP is added on as another
   feature.

   As explained above, traffic across the ACP SHOULD still be end-to-end
   encrypted whenever possible.  This includes traffic such as GRASP,
   EST and BRSKI inside objective?
      If not, diagnose SLAAC/ND state.

   o  When did we last attempt to build an ACP secure channel to the ACP.  This minimizes man in
      neighbor?

   o  If it failed, why:

      *  Did the middle
   attacks by compromised ACP group members.  Such attackers cannot
   eavesdrop neighbor close the connection on us or modify communications, they can just filter them (which
   is unavoidable by any means).

   Further security can be achieved by constraining communication
   patterns inside did we close the ACP, for example through roles that could be
   encoded into
         connection on it because the domain certificates.  This is subject for future
   work.

9.3.  The Administrator View

   An ACP is self-forming, self-managing and self-protecting, therefore
   has minimal dependencies certificate membership
         failed?

      *  If the neighbor closed the connection on us, provide any error
         diagnostics from the administrator of secure channel protocol.

      *  If we failed the network.
   Specifically, since it is independent of configuration, there is attempt, display our local reason:

         +  There was no
   scope for configuration errors on common secure channel protocol supported by the
            two neighbors (this could not happen on nodes supporting
            this specification because it mandates common support for
            IPsec).

         +  The ACP itself. domain certificate membership check (Section 6.1.2)
            fails:

            -  The administrator
   may neighbors certificate does not have the option to enable or disable required
               trust anchor.  Provide diagnostics which trust anchor it
               has (can identify whom the entire approach, but
   detailed configuration is device belongs to).

            -  The neighbors certificate does not possible.  This means that have the ACP must same domain
               (or no domain at all).  Diagnose domain-name and
               potentially other other cert info.

            -  The neighbors certificate has been revoked or could not
               be reflected in the running configuration of nodes, except a
   possible on/off switch.

   While configuration authenticated by OCSP.

            -  The neighbors certificate has expired - or is not possible, an administrator must have full
   visibility of yet
               valid.

      *  Any other connection issues in e.g., IKEv2 / IPsec, DTLS?.

   Question: Is the ACP and all operating correctly across its parameters, to be able to do
   trouble-shooting.  Therefore, an secure channels?

   o  Are there one or more active ACP must support all show and debug
   options, as neighbors with secure channels?

   o  Is the RPL routing protocol for any other network function.  Specifically, a network
   management system or controller must be able to discover the ACP, and
   monitor its health.  This visibility of ACP operations must clearly
   be separated from visibility of data-plane so automated systems will
   never have running?

   o  Is there a default route to deal with the root in the ACP aspect unless they explicitly desire to
   do so.

   Since an routing table?
   o  Is there for each direct ACP is self-protecting, a node neighbor not supporting reachable over the ACP, or
   without a valid domain certificate cannot connect ACP
      virtual interface to it.  This means
   that by default the root a traditional controller or network management system
   cannot connect to an ACP.  See Section 8.1.1 for more details route in the ACP routing table?

   o  Is ACP GRASP running?

   o  Is at least one SRV.est objective cached (to support certificate
      renewal)?

   o  Is there at least one BRSKI registrar objective cached (in case
      BRSKI is supported)

   o  Is BRSKI proxy operating normally on how
   to connect an NMS host into all interfaces where ACP is
      operating?

   o  ...

   These lists are not necessarily complete, but illustrate the ACP.

10.  Further Considerations (Informative)

   The following sections cover topics
   principle and show that there are beyond the primary cope variety of this document (e.g.: bootstrap), that explain decisions made issues ranging from
   normal operational causes (a neighbor in
   this document (e.g.: choice of GRASP) or that explain desirable
   extensions or implementation details for the another ACP that are not
   considered to be appropriate to standardize domain) over
   problems in this document.

10.1.  BRSKI Bootstrap (ANI)

   [I-D.ietf-anima-bootstrapping-keyinfra] (BRSKI) describes the credentials management (certificate lifetimes),
   explicit security actions (revocation) or unexpected connectivity
   issues (intervening L2 equipment).

   The items so far are illustrating how nodes
   with an IDevID certificate the ANI operations can securely and zero-touch enroll be
   diagnosed with a
   domain certificate (LDevID) to support the ACP.  BRSKI also leverages
   the ACP to enable zero touch bootstrap passive observation of new nodes across networks
   without any configuration requirements across the transit nodes
   (e.g.: no DHCP/DS forwarding/server setup). operational state of its
   components including historic/cached/counted events.  This includes otherwise is not configured networks as described in Section 3.2.  Therefore BRSKI
   in conjunction with
   necessary sufficient to provide good enough diagnostics overall:

   The components of ACP provides for a secure and zero-touch
   management solution for complete networks.  Nodes supporting such an
   infrastructure (BRSKI and ACP) BRSKI are called ANI nodes (Autonomic
   Networking Infrastructure), see [I-D.ietf-anima-reference-model].
   Nodes that designed with security in mind
   but they do not support an IDevID but only an (insecure) vendor
   specific Unique Device Identifier (UDI) or nodes whose manufacturer attempt to provide diagnostics for building the
   network itself.  Consider two examples:

   1.  BRSKI does not support allow for a MASA could use some future security reduced
   version of BRSKI.

   When BRSKI is used neighboring device to provision a domain identify the
       pledges certificate (which is called
   enrollment), (IDevID).  Only the selected BRSKI registrar (acting as an EST server) must include the
   subjectAltName / rfc822Name encoded ACP address and domain name
       can do this, but it may be difficult to
   the enrolling node (called pledge) via its response disseminate information
       about undesired pledges from those BRSKI registrars to the locations/
       nodes where information about those pledges
   EST CSR Attribute request that is mandatory in BRSKI.

   The Certificate Authority in an ACP network must not change the
   subjectAltName / rfc822Name in the certificate. desired.

   2.  The ACP Link Layer Discovery Protocol (LLDP, [LLDP]) disseminates
       information about nodes can
   therefore find to their ACP address and domain using this field in the
   domain certificate, both for themselves, as well immediate neighbors, such as for other nodes.

   The use of BRSKI in conjunction with the ACP can also help to further
   simplify maintenance
       node model/type/software and renewal of domain certificates.  Instead interface name/number of
   relying on CRL, the lifetime of certificates can be made extremely
   small, for example
       connection.  This information is often helpful or even necessary
       in the order of hours.  When a node fails to
   connect network diagnostics.  It can equally considered to the ACP within its certificate lifetime, it cannot connect be too
       insecure to the ACP make this information available unprotected to renew its certificate across it (using just EST), but
   it all
       possible neighbors.

   An "interested adjacent party" can still renew its certificate as an "enrolled/expired pledge"
   via always determine the IDevID of a
   BRSKI bootstrap proxy.  This requires only that the pledge by behaving like a BRSKI
   registrar honors expired domain certificates and that proxy/registrar.  Therefore the
   IDevID of a BRSKI pledge
   first attempts is not meant to perform TLS authentication for BRSKI bootstrap with
   its expired domain certificate be protected - and only reverts it just has
   to its IDevID when
   this fails.  This mechanism could also render CRLs unnecessary
   because the BRSKI registrar in conjunction with the CA would be queried and is not
   renew revoked certificates - only a "no-not-renew" list signaled unsolicited (as it would be
   necessary in
   LLDP) so that other observers on registrars/CA.

   In the absence of BRSKI or less secure variants thereof, provisioning
   of certificates may involve one or more touches or non-standardized
   automation.  Node vendors usually support provisioning of
   certificates into nodes via PKCS#7 (see [RFC2315]) and may support
   this provisioning through vendor specific models via Netconf
   ([RFC6241]).  If such nodes also support Netconf Zero-Touch
   ([I-D.ietf-netconf-zerotouch]) then this same subnet can determine who is
   an "interested adjacent party".

   Desirable options for additional diagnostics subject to future work
   include:

   1.  Determine if LLDP should be combined a recommended functionality for ANI
       devices to zero-
   touch provisioning of domain certificates into nodes.  Unless there
   are equivalent integration improve diagnostics, and if so, which information
       elements it should signal (insecure).

   2.  In alternative to LLDP, A DULL GRASP diagnostics objective could
       be defined to carry these information elements.

   3.  The IDevID of Netconf connections across BRSKI pledges should be included in the selected
       insecure diagnostics option.

   4.  A richer set of diagnostics information should be made available
       via the secured ACP as
   there is in BRSKI, this combination would not support zero-touch
   bootstrap across a not configured channels, using either single-hop GRASP or
       network though.

10.2. wide "topology discovery" mechanisms.

10.3.  ACP (and BRSKI) Diagnostics

   Even though Registrar Considerations

   As described in Section 6.10.7, the ACP addressing mechanism is
   designed to enable lightweight, distributed and ANI in general uncoordinated ACP
   registrars that are taking out many manual
   configuration mistakes through their automation, it is important providing ACP address prefixes to
   provide good diagnostics for them.

   The basic diagnostics is support of (yang) data models representing
   the complete (auto-)configuration candidate ACP
   nodes by enrolling them with an ACP domain certificate into an ACP
   domain via any appropriate mechanism/protocol, automated or not.

   This section discusses informatively more details and operational state of all
   components: BRSKI, GRASP, options for ACP
   registrars.

10.3.1.  Registrar interactions

   This section summarizes and discusses the infrastructure used interactions with other
   entities required by them:
   TLS/dTLS, IPsec, certificates, an ACP registrar.

   In a simple instance of an ACP network, no central NOC component
   beside a trust anchors, time, VRF and so on.
   While necessary, this anchor (root CA) is not sufficient:

   Simply representing required.  One or more
   uncoordinated acting ACP registrar can be set up, performing the state of components does not allow operators
   to quickly take action - unless they do understand how to interpret
   following interactions:

   To orchestrate enrolling a candidate ACP node autonomically, the data, ACP
   registrar can rely on the ACP and use Proxies to reach the candidate
   ACP node, therefore allowing minimum pre-existing (auto-)configured
   network services on the candidate ACP node.  BRSKI defines the BRSKI
   proxy, a design that can mean a requirement be adopted for deep understanding various protocols that
   Pledges/candidate ACP nodes could want to use, for example BRSKI over
   CoAP (Constrained Application Protocol), or proxying of Netconf.

   To reach a trust anchor unaware of
   all components and how they interact in the ACP/ANI.

   Diagnostic supports should help to quickly answer ACP, the questions
   operators are expected to ask, such as "is ACP registrar would
   use the Data-Plane.  ACP working correctly
   ?", or "why is there no and Data-Plane in an ACP connection to a known neighboring node ?"

   In current registrar could
   (and by default should be) completely isolated from each other at the
   network management approaches, level.  Only applications like the logic ACP registrar would need
   the ability for their transport stacks to answer these
   questions is most often built as centralized diagnostics software
   that leverages access both.

   In non autonomic enrollment options, the above mentioned data models.  While this approach
   is feasible for components utilizing plane between a ACP
   registrar and the ANI, it is not sufficient candidate ACP node needs to
   diagnose be configured first.
   This includes the ANI itself:

   o  Developing ACP registrar and the logic candidate ACP node.  Then any
   appropriate set of protocols can be used between ACP registrar and
   candidate ACP node to identify common issues requires
      operational experience with discover the components of other side, and then connect and
   enroll (configure) the ANI.  Letting
      each management system define its own analysis candidate ACP node with an ACP domain
   certificate.  Netconf ZeroTouch ([I-D.ietf-netconf-zerotouch]) is inefficient.  As
      much as possible, future work should attempt an
   example protocol that could be used for this.  BRSKI using optional
   discovery mechanisms is equally a possibility for candidate ACP nodes
   attempting to standardize data
      models that support common error diagnostic.

   o  When be enrolled across non-ACP networks, such as the ANI is not operating correctly, it may
   Internet.

   When candidate ACP nodes have secure bootstrap, like BRSKI Pledges,
   they will not trust to be possible configured/enrolled across the network,
   unless being presented with a voucher (see [RFC8366]) authorizing the
   network to
      run diagnostics from remote because take posession of missing connectivity.  The
      ANI should therefore have diagnostic capabilities available
      locally on the nodes themselves.

   o  Certain operations are difficult or impossible node.  An ACP registrar will then
   need a method to monitor in real-
      time, retrieve such as initial bootstrap issues in a network location where
      no voucher, either offline, or online
   from a MASA (Manufacturer Authorized Signing Authority).  BRSKI and
   Netconf ZeroTouch are two protocols that include capabilities exist to attach local diagnostics.  Therefore it
      is important
   present the voucher to also define means of capturing (logging)
      diagnostics locally for later retrieval.  Ideally, these captures
      are also non-volatile so that they can survive extended power-off
      conditions - the candidate ACP node.

   An ACP registrar could operate EST for example when ACP certificate renewal and/or
   act as a device that fails CRL Distribution point.  A node performing these services
   does not need to be brought up
      zero-touch is being sent back for diagnostics at a more
      appropriate location. support performing (initial) enrollment, but it does
   require the same above described connectivity as an ACP registrar:
   via the ACP to ACP nodes and via the Data-Plane to the trust anchor
   and other sources of CRL information.

10.3.2.  Registrar Parameter

   The most simple form interactions of diagnostics answering questions like the an ACP registrar outlined Section 6.10.7 and
   Section 10.3.1 above is depend on the following parameters:

      A URL to represent the relevant information sequentially in
   dependency order, trust anchor (root CA) and credentials so that the first non-expected/non-operational item
   is
      ACP registrar can let the most likely root cause.  Or just log/highlight that item.  For
   example:

   Q: Is trust anchor sign candidate ACP operational member
      certificates.

      The ACP domain-name.

      The Registrar-ID to accept neighbor connections:

   o  Check if any potentially necessary configuration use.  This could default to make ACP/ANI
      operational are correct (see Section 10.3 for a discussion MAC address of such
      commands).

   o  Does the system time look reasonable, or could it be
      the default
      system time after clock chip battery failure (certificate checks
      depend on reasonable notion of time).

   o  Does ACP registrar.

      For recovery, the node have keying material - domain certificate, trust
      anchors.

   o  If no keying material next-useable Node-IDs for zone (Zone-ID=0) sub-
      addressing scheme, for Vlong /112 and ANI is supported/enabled, check the
      state of BRSKI (not detailed for Vlong /1120 sub-
      addressing scheme.  These IDs would only need to be provisioned
      after recovering from a crash.  Some other mechanism would be
      required to remember these IDs in this example).

   o  Check a backup location or to recover
      them from the validity set of the currently known ACP nodes.

      Policies if candidate ACP nodes should receive a domain certificate:

      *  Does the
      certificate authenticate against or not, for example based on the trust anchor ?

      *  Has it been revoked ?

      *  Was devices LDevID as in
      BRSKI.  The ACP registrar may have a whitelist or blacklist of
      devices serialNumbers from teir LDevID.

      Policies what type of address prefix to assign to a candidate ACP
      devices, based on likely the last scheduled attempt same information.

      For BRSKI or other mechanisms using vouchers: Parameters to
      determine how to retrieve a CRL successful
         (e.g.: do we know that our CRL vouchers for specific type of secure
      bootstrap candidate ACP nodes (such as MASA URLs), unless this
      information is up to date).

      *  Is automatically learned such as from the certificate valid: validity start time LDevID of
      candidate ACP nodes (as defined in BRSKI).

10.3.3.  Certificate renewal and limitations

   When an ACP node renews/rekeys its certificate, it may end up doing
   so via a different registrar (e.g., EST server) than the past,
         expiration time in one it
   originally received its ACP domain certificate from, for example
   because that original ACP registrar is gone.  The ACP registrar
   through which the future ?

      *  Does renewal/rekeying is performed would by default
   trust the certificate have a correctly formatted ACP domain information
         field ?

   o  Was from the ACP VRF successfully created ?

   o  Is nodes current ACP enabled on one or more interfaces that are up
   domain certificate and running ?

   If all maintain this looks good, information so that the ACP should be running locally "fine" -
   but we did not check any node
   maintains its ACP neighborships.

   Question: why does address prefix.  In EST renewal/rekeying, the node not create a working ACP connection
   nodes current ACP domain certificate is signaled during the TLS
   handshake.

   This simple scenario has two limitations:

   1.  The ACP registrars can not directly assign certificates to a
   neighbor on nodes
       and therefore needs an interface ?

   o  Is "online" connection to the interface physically up ? Does it have trust anchor
       (root CA).

   2.  Recovery from a compromised ACP registrar is difficult.  When an IPv6 link-local
      address ?

   o  Is
       ACP registrar is compromised, it enabled can insert for example
       conflicting ACP ?

   o  Do we successfully send DULL GRASP messages to the interface (link
      layer errors) ?

   o  Do we receive DULL GRASP messages on the interface ? If not, some
      intervening L2 equipment performing bad MLD snooping could have
      caused problems.  Provide e.g.: diagnostics of the MLD querier
      IPv6 domain information and MAC address.

   o  Do we see create thereby an attack
       against other ACP nodes through the ACP objective in any DULL GRASP message from that
      interface ? Diagnose routing protocol.

   Even when such a malicious ACP registrar is detected, resolving the supported secure channel methods.

   o  Do we know
   problem may be difficult because it would require identifying all the MAC address
   wrong ACP domain certificates assigned via the ACP registrar after it
   was was compromised.  And without additional centralized tracking of
   assigned certificates there is no way to do this - assuming one can
   not retrieve this information from the neighbor .

10.3.4.  ACP Registrars with sub-CA

   In situations, where either of the above two limitations are an
   issue, ACP objective
      ? If not, diagnose SLAAC/ND state.

   o  When did we last attempt registrars could also be sub-CAs.  This removes the need
   for connectivity to build a root-CA whenever an ACP secure channel to the
      neighbor ?

   o  If it failed, why:

      *  Did the neighbor close the connection on us or did we close node is enrolled, and
   reduces the
         connection on need for connectivity of such an ACP registrar to a root-
   CA to only those times when it because the domain certificate membership
         failed ?

      *  If the neighbor closed the connection on us, provide any error
         diagnostics from the secure channel protocol.

      *  If we failed the attempt, display our local reason:

         +  There was no common secure channel protocol supported by needs to renew its own certificate.
   The ACP registrar would also now use its own (sub-CA) certificate to
   enroll and sign the
            two neighbors (this could not happen on ACP nodes supporting
            this specification because certificates, and therefore it mandates common support for
            IPsec).

         +  The is only
   necessary to revoke a compromised ACP domain registrars sub-CA certificate.
   Or let it expire and not renew it, when the certificate of the sub-CA
   is appropriately short-lived.

   As the ACP domain membership check (Section 6.1.2)
            fails:

            -  The neighbors certificate does not have the required
               trust anchor.  Provide diagnostics which verifies a peer ACP node's ACP
   domain certicate trust anchor chain, it
               has (can identify whom will also verify the device belongs to).

            -  The neighbors signing
   certificate does not have which is the same domain
               (or no compromised/revoked sub-CA certificate.
   Therefore ACP domain at all).  Diagnose domain-name membership for an ACP node enrolled from a
   compromised ACP registrar will fail.

   ACP nodes enrolled by a compromised ACP registrar would automatically
   fail to establish ACP channels and
               potentially other other cert info.

            -  The neighbors ACP domain certificate has been revoked or could not
               be authenticated by OCSP.

            -  The neighbors renewal via
   EST and therefore revert to their role as a candidate ACP members and
   attempt to get a new ACP domain certificate has expired from an ACP registrar - or is not yet
               valid.

      *  Any other connection issues in e.g.: IKEv2 / IPsec, dTLS ?".

   Question: Is the
   for example via BRSKI.  In result, ACP operating correctly across its secure channels
   ?:

   o  Are there one or more active registrars that have an
   associated sub-CA makes isolating and resolving issues with
   compromised registrars easier.

   Note that ACP neighbors registrars with secure channels ?

   o  Is the RPL routing protocol for sub-CA functionality also can control
   the lifetime of ACP running ?

   o  Is there domain certificates easier and therefore also be
   used as a default route tool to introduce short lived certificates and not rely on
   CRL, whereas the root in certificates for the sub-CAs themselves could be
   longer lived and subject to CRL.

10.3.5.  Centralized Policy Control

   When using multiple, uncoordinated ACP routing table ?

   o  Is there registrars, several advanced
   operations are potentially more complex than with a single, resilient
   policy control backend, for each direct example including but not limited to:

      Which candidate ACP neighbor node is permitted or not reachable over the permitted into an ACP
      virtual interface
      domain.  This may not be a decision to the root be taken upfront, so that a route in the ACP routing table ?

   o  Is
      per-serialNumber policy can be loaded into ever ACP GRASP running ?

   o  Is at least one SRV.est objective cached (to support certificate
      renewal) ?

   o  Is there at least one BRSKI registrar objective cached (in case
      BRSKI is supported)

   o  Is BRSKI proxy operating normally on registrar.
      Instead, it may better be decided in real-time including
      potentially a human decision in a NOC.

      Tracking of all interfaces where enrolled ACP is
      operating ?

   o  ...

   These lists are not necessarily complete, but illustrate the
   principle nodes and show that there are variety of issues ranging from
   normal operational causes (a neighbor their certificate
      information.  For example in another support of revoking individual ACP domain) over
   problems in the credentials management (certificate lifetimes),
   explicit security actions (revocation)
      nodes certificates.

      More flexible policies what type of address prefix or unexpected connectivity
   issues (intervening L2 equipment).

   The items even what
      specific address prefix to assign to a candidate ACP node.

   These and other operations could be introduced more easily by
   introducing a centralized Policy Management System (PMS) and
   modifying ACP registrar behavior so far are illustrating how that it queries the ANI operations can be
   diagnosed with passive observation of PMS for any
   policy decision occuring during the operational state of its
   components including historic/cached/counted events.  This is not
   necessary sufficient candidate ACP node enrollment
   process and/or the ACP node certificate renewal process.  For
   example, which ACP address prefix to provide good enough diagnostics overall:

   The components of assign.  Likewise the ACP and BRSKI are designed with security in mind
   but they do not attempt
   registrar would report any relevant state change information to provide diagnostics for building the
   network itself.  Consider two examples:

   1.  BRSKI does not allow
   PMS as well, for example when a neighboring device to identify the
       pledges certificate (IDevID).  Only was successfully enrolled
   onto a candidate ACP node.  Such an ACP registrar PMS interface
   definition is subject to future work.

10.4.  Address Space Considerations

   This document defines the selected BRSKI-registrar
       can do this, but it may be difficult Zone, Vlong and Manual sub address schemes
   primarily to disseminate information
       about undesired pledges from those support address prefix assignment via distributed,
   potentially uncoordinated ACP registrars to locations/nodes
       where information about those pledges is desired.

   2.  LLDP disseminates information about nodes to their immediate
       neighbors, such as node model/type/software and interface name/
       number of the connection.  This information is often helpful or
       even necessary defined in network diagnostics.  It
   Section 6.10.7.  This costs 48/46 bit identifier so that these ACP
   registrar can equally considered
       to be too insecure to make this information available unprotected assign non-conflicting address prefixes.  This design
   does not leave enough bits to all possible neighbors.

   An "interested adjacent party" can always determine the IDevID of simultaneously support a
   BRSKI pledge by behaving like large number
   of nodes (Node-ID) plus a BRSKI proxy/registrar.  Therefore the
   IDevID large prefix of local addresses for every
   node plus a BRSKI pledge is not meant large enough set of bits to be protected - it just has identify a routing Zone.  In
   result, Zone, Vlong 8/16 attempt to be queried and is not signaled unsolicited (as it would be support all features, but in
   LLDP) so via
   separate prefixes.

   In networks that other observers always expect to rely on a centralized PMS as
   described above (Section 10.3.5), the same subnet can determine who is
   an "interested adjacent party".

   Desirable options 48/46 bits for additional diagnostics subject to the Registrar-ID
   could be saved.  Such variations of the ACP addressing mecchanisms
   could be introduct through future work
   include:

   1.  Determine if LLDP should in different ways.  If the
   prefix rfcSELF in the ACP information field was changed, incompatible
   ACP variations could be created where every design aspect of the ACP
   could be changed.  Including all addressing choices.  If instead a recommended functionality for ANI
       devices to improve diagnostics, and if so, which information
       elements
   new addressing sub-type would be defined, it should signal (insecure).

   2.  In alternative to LLDP, A DULL GRASP diagnostics objective could be defined to carry these information elements.

   3.  The IDevID a backward
   compatible extension of BRSKI pledges should this ACP specification.  Information such as
   the size of a zone-prefix and the length of the prefix assigned to
   the ACP node itself could be included in encoded via the selected
       insecure diagnostics option.

   4.  A richer set extension field of the
   ACP domain information.

   Note that an explicitly defined "Manual" addressing sub-scheme is
   always beneficial to provide an easy way for ACP nodes to prohibit
   incorrect manual configuration of diagnostics information should be made available any non-"Manual" ACP address spaces
   and therefore ensure hat "Manual" operations will never impact
   correct routing for any non-"Manual" ACP addresses assigned via the secured ACP channels, using either single-hop GRASP or
       network wide "topology discovery" mechanisms.

10.3.
   domain certificates.

10.5.  Enabling and disabling ACP/ANI

   Both ACP and BRSKI require interfaces to be operational enough to
   support sending/receiving their packets.  In node types where
   interfaces are by default (e.g.: (e.g., without operator configuration)
   enabled, such as most L2 switches, this would be less of a change in
   behavior than in most L3 devices (e.g.: routers), where interfaces
   are by default disabled.  In almost all network devices it is common
   though for configuration to change interfaces to a physically
   disabled state and that would break the ACP.

   In this section, we discuss a suggested operational model to enable/
   disable interfaces and nodes for ACP/ANI in a way that minimizes the
   risk of operator action to break the ACP in this way, and that also
   minimizes operator surprise when ACP/ANI becomes supported in node
   software.

10.3.1.

10.5.1.  Filtering for non-ACP/ANI packets

   Whenever this document refers to enabling an interface for ACP (or
   BRSKI), it only requires to permit the interface to send/receive
   packets necessary to operate ACP (or BRSKI) - but not any other data-
   plane Data-
   Plane packets.  Unless the data-plane Data-Plane is explicitly configured/
   enabled, all packets not required for ACP/BRSKI should be filtered on
   input and output:

   Both BRSKI and ACP require link-local only IPv6 operations on
   interfaces and DULL GRASP.  IPv6 link-local operations means the
   minimum signaling to auto-assign an IPv6 link-local address and talk
   to neighbors via their link-local address: SLAAC (Stateless Address
   Auto-Configuration - [RFC4862]) and ND (Neighbor Discovery -
   [RFC4861]).  When the device is a BRSKI pledge, it may also require
   TCP/TLS connections to BRSKI proxies on the interface.  When the
   device has keying material, and the ACP is running, it requires DULL
   GRASP packets and packets necessary for the secure-channel mechanism
   it supports, e.g.: e.g., IKEv2 and IPsec ESP packets or dTLS DTLS packets to the
   IPv6 link-local address of an ACP neighbor on the interface.  It also
   requires TCP/TLS packets for its BRSKI proxy functionality, if it
   does support BRSKI.

10.3.2.

10.5.2.  Admin Down State

   Interfaces on most network equipment have at least two states: "up"
   and "down".  These may have product specific names.  "down" for
   example could be called "shutdown" and "up" could be called "no
   shutdown".  The "down" state disables all interface operations down
   to the physical level.  The "up" state enables the interface enough
   for all possible L2/L3 services to operate on top of it and it may
   also auto-enable some subset of them.  More commonly, the operations
   of various L2/L3 services is controlled via additional node-wide or
   interface level options, but they all become only active when the
   interface is not "down".  Therefore an easy way to ensure that all
   L2/L3 operations on an interface are inactive is to put the interface
   into "down" state.  The fact that this also physically shuts down the
   interface is in many cases just a side effect, but it may be
   important in other cases (see below).

   To provide ACP/ANI resilience against operators configuring
   interfaces to "down" state, this document recommends to separate the
   "down" state of interfaces into an "admin down" state where the
   physical layer is kept running and ACP/ANI can use the interface and
   a "physical down" state.  Any existing "down" configurations would
   map to "admin down".  In "admin down", any existing L2/L3 services of
   the data-plane Data-Plane should see no difference to "physical down" state.  To
   ensure that no data-plane Data-Plane packets could be sent/received, packet
   filtering could be established automatically as described above in
   Section 10.3.1. 10.5.1.

   As necessary (see discussion below) new configuration options could
   be introduced to issue "physical down".  The options should be
   provided with additional checks to minimize the risk of issuing them
   in a way that breaks the ACP without automatic restoration.  For
   example they could be denied to be issued from a control connection
   (netconf/ssh) that goes across the interface itself ("do not
   disconnect yourself").  Or they could be performed only temporary and
   only be made permanent with additional later reconfirmation.

   In the following sub-sections important aspects to the introduction
   of "admin down" state are discussed.

10.3.2.1.

10.5.2.1.  Security

   Interfaces are physically brought down (or left in default down
   state) as a form of security.  "Admin down" state as described above
   provides also a high level of security because it only permits ACP/
   ANI operations which are both well secured.  Ultimately, it is
   subject to security review for the deployment whether "admin down" is
   a feasible replacement for "physical down".

   The need to trust into the security of ACP/ANI operations need to be
   weighed against the operational benefits of permitting this: Consider
   the typical example of a CPE (customer premises equipment) with no
   on-site network expert.  User ports are in physical down state unless
   explicitly configured not to be.  In a misconfiguration situation,
   the uplink connection is incorrectly plugged into such a user port.
   The device is disconnected from the network and therefore no
   diagnostics from the network side is possible anymore.
   Alternatively, all ports default to "admin down".  The ACP (but not
   the data-plane) Data-Plane) would still automatically form.  Diagnostics from the
   network side is possible and operator reaction could include to
   either make this port the operational uplink port or to instruct re-
   cabling.  Security wise, only ACP/ANI could be attacked, all other
   functions are filtered on interfaces in "admin down" state.

10.3.2.2.

10.5.2.2.  Fast state propagation and Diagnostics

   "Physical down" state propagates on many interface types (e.g.: (e.g.,
   Ethernet) to the other side.  This can trigger fast L2/L3 protocol
   reaction on the other side and "admin down" would not have the same
   (fast) result.

   Bringing interfaces to "physical down" state is to the best of our
   knowledge always a result of operator action, but today, never the
   result of (autonomic) L2/L3 services running on the nodes.  Therefore
   one option is to change the operator action to not rely on link-state
   propagation anymore.  This may not be possible when both sides are
   under different operator control, but in that case it is unlikely
   that the ACP is running across the link and actually putting the
   interface into "physical down" state may still be a good option.

   Ideally, fast physical state propagation is replaced by fast software
   driven state propagation.  For example a DULL GRASP "admin-state"
   objective could be used to autoconfigure auto configure a BFD Bidirectional Forwarding
   Protocol (BFD, [RFC5880]) session between the two sides of the link
   that would be used to propagate the "up" vs. admin down state.

   Triggering physical down state may also be used as a mean of
   diagnosing cabling in the absence of easier methods.  It is more
   complex than automated neighbor diagnostics because it requires
   coordinated remote access to both (likely) sides of a link to
   determine whether up/down toggling will cause the same reaction on
   the remote side.

   See Section 10.2 for a discussion about how LLDP and/or diagnostics
   via GRASP could be used to provide neighbor diagnostics, and
   therefore hopefully eliminating the need for "physical down" for
   neighbor diagnostics - as long as both neighbors support ACP/ANI.

10.3.2.3.

10.5.2.3.  Low Level Link Diagnostics

   "Physical down" is performed to diagnose low-level interface behavior
   when higher layer services (e.g.: (e.g., IPv6) are not working.  Especially
   Ethernet links are subject to a wide variety of possible wrong
   configuration/cablings if they do not support automatic selection of
   variable parameters such as speed (10/100/1000 Mbps), crossover
   (Auto-MDIX) and connector (fiber, copper - when interfaces have
   multiple but can only enable one at a time).  The need for low level
   link diagnostic can therefore be minimized by using fully
   autoconfiguring auto
   configuring links.

   In addition to "Physical down", low level diagnostics of Ethernet or
   other interfaces also involve the creation of other states on
   interfaces, such as physical loopback Loopback (internal and/or external) or
   bringing down all packet transmissions for reflection/cable-length
   measurements.  Any of these options would disrupt ACP as well.

   In cases where such low-level diagnostics of an operational link is
   desired but where the link could be a single point of failure for the
   ACP, ASA on both nodes of the link could perform a negotiated
   diagnostics that automatically terminates in a predetermined manner
   without dependence on external input ensuring the link will become
   operational again.

10.3.2.4.

10.5.2.4.  Power Consumption

   Power consumption of "physical down" interfaces may be significantly
   lower than those in "admin down" state, for example on long range
   fiber interfaces.  Assuming reasonable clocks on devices, mechanisms
   for infrequent periodic probing could allow to automatically
   establish ACP connectivity across such links.  Bring up interfaces
   for 5 seconds to probe if there is an ACP neighbor on the remote end
   every 500 seconds = 1% power consumption.

10.3.3.

10.5.3.  Interface level ACP/ANI enable

   The interface level configuration option "ACP enable" enables ACP
   operations on an interface, starting with ACP neighbor discovery via
   DULL GRAP.  The interface level configuration option "ANI enable" on
   nodes supporting BRSKI and ACP starts with BRSKI pledge operations
   when there is no domain certificate on the node.  On ACP/BRSKI nodes,
   "ACP enable" may not need to be supported, but only "ANI enable".
   Unless overridden by global configuration options (see later), "ACP/
   ANI enable" will result in "down" state on an interface to behave as
   "admin down".

10.3.4.

10.5.4.  Which interfaces to auto-enable ? auto-enable?

   (Section 6.3) requires that "ACP enable" is automatically set on
   native interfaces, but not on non-native interfaces (reminder: a
   native interface is one that exists without operator configuration
   action such as physical interfaces in physical devices).

   Ideally, ACP enable is set automatically on all interfaces that
   provide access to additional connectivity that allows to reach more
   nodes of the ACP domain.  The best set of interfaces necessary to
   achieve this is not possible to determine automatically.  Native
   interfaces are the best automatic approximation.

   Consider an ACP domain of ACP nodes transitively connected via native
   interfaces.  A data-plane Data-Plane tunnel between two of these nodes that are
   non-adjacent is created and "ACP enable" is set for that tunnel.  ACP
   RPL sees this tunnel as just as a single hop.  Routes in the ACP
   would use this hop as an attractive path element to connect regions
   adjacent to the tunnel nodes.  In result, the actual hop-by-hop paths
   used by traffic in the ACP can become worse.  In addition, correct
   forwarding in the ACP now depends on correct data-plane Data-Plane forwarding
   config including QoS, filtering and other security on the data-plane Data-Plane
   path across which this tunnel runs.  This is the main issue why "ACP/
   ANI enable" should not be set automatically on non-native interfaces.

   If the tunnel would connect two previously disjoint ACP regions, then
   it likely would be useful for the ACP.  A data-plane Data-Plane tunnel could
   also run across nodes without ACP and provide additional connectivity
   for an already connected ACP network.  The benefit of this additional
   ACP redundancy has to be weighed against the problems of relying on
   the data-plane. Data-Plane.  If a tunnel connects two separate ACP regions: how
   many tunnels should be created to connect these ACP regions reliably
   enough ?
   enough?  Between which nodes ? nodes?  These are all standard tunneled
   network design questions not specific to the ACP, and there are no
   generic fully automated answers.

   Instead of automatically setting "ACP enable" on these type of
   interfaces, the decision needs to be based on the use purpose of the
   non-native interface and "ACP enable" needs to be set in conjunction
   with the mechanism through which the non-native interface is created/
   configured.

   In addition to explicit setting of "ACP/ANI enable", non-native
   interfaces also need to support configuration of the ACP RPL cost of
   the link - to avoid the problems of attracting too much traffic to
   the link as described above.

   Even native interfaces may not be able to automatically perform BRSKI
   or ACP because they may require additional operator input to become
   operational.  Example include DSL interfaces requiring PPPoE
   credentials or mobile interfaces requiring credentials from a SIM
   card.  Whatever mechanism is used to provide the necessary config to
   the device to enable the interface can also be expanded to decide on
   whether or not to set "ACP/ANI enable".

   The goal of automatically setting "ACP/ANI enable" on interfaces
   (native or not) is to eliminate unnecessary "touches" to the node to
   make its operation as much as possible "zero-touch" with respect to
   ACP/ANI.  If there are "unavoidable touches" such a creating/
   configuring a non-native interface or provisioning credentials for a
   native interface, then "ACP/ANI enable" should be added as an option
   to that "touch".  If a wrong "touch" is easily fixed (not creating
   another high-cost touch), then the default should be not to enable
   ANI/ACP, and if it is potentially expensive or slow to fix (e.g.: (e.g.,
   parameters on SIM card shipped to remote location), then the default
   should be to enable ACP/ANI.

10.3.5.

10.5.5.  Node Level ACP/ANI enable

   A node level command "ACP/ANI enable [up-if-only]" enables ACP or ANI
   on the node (ANI = ACP + BRSKI).  Without this command set, any
   interface level "ACP/ANI enable" is ignored.  Once set, ACP/ANI will
   operate interface where "ACP/ANI enable" is set.  Setting of
   interface level "ACP/ANI enable" is either automatic (default) or
   explicit through operator action as described in the previous
   section.

   If the option "up-if-only" is selected, the behavior of "down"
   interfaces is unchanged, and ACP/ANI will only operate on interfaces
   where "ACP/ANI enable" is set and that are "up".  When it is not set,
   then "down" state of interfaces with "ACP/ANI enable" is modified to
   behave as "admin down".

10.3.5.1.

10.5.5.1.  Brownfield nodes

   A "brownfield" node is one that already has a configured data-plane. Data-Plane.

   Executing global "ACP/ANI enable [up-if-only]" on each node is the
   only command necessary to create an ACP across a network of
   brownfield nodes once all the nodes have a domain certificate.  When
   BRSKI is used ("ANI enable"), provisioning of the certificates only
   requires set-up of a single BRSKI-registrar BRSKI registrar node which could also
   implement a CA for the network.  This is the most simple way to
   introduce ACP/ANI into existing (== brownfield) networks.

   The need to explicitly enable ACP/ANI is especially important in
   brownfield nodes because otherwise software updates may introduce
   support for ACP/ANI: Automatic enablement of ACP/ANI in networks
   where the operator does not only not want ACP/ANI but where he likely
   never even heard of it could be quite irritating to him.  Especially
   when "down" behavior is changed to "admin down".

   Automatically setting "ANI enable" on brownfield nodes where the
   operator is unaware of it could also be a critical security issue
   depending on the vouchers used by BRKSI on these nodes.  An attacker
   could claim to be the owner of these devices and create an ACP that
   the attacker has access/control over.  In network where the operator
   explicitly wants to enable the ANI this could not happen, because he
   would create a BRSKI registrar that would discover attack attempts.
   Nodes requiring "ownership vouchers" would not be subject to that
   attack.  See [I-D.ietf-anima-bootstrapping-keyinfra] for more
   details.  Note that a global "ACP enable" alone is not subject to
   these type of attacks, because it always depends on some other
   mechanism first to provision domain certificates into the device.

10.3.5.2.

10.5.5.2.  Greenfield nodes

   A "greenfield" node is one that did not have any prior configuration.

   For greenfield nodes, only "ANI enable" is relevant.  If another
   mechanism than BRSKI is used to (zero-touch) bootstrap a node, then
   it is up to that mechanism to provision domain certificates and to
   set global "ACP enable" as desired.

   Nodes supporting full ANI functionality set "ANI enable"
   automatically when they decide that they are greenfield, e.g.: e.g., that
   they are powering on from factory condition.  They will then put all
   native interfaces into "admin down" state and start to perform BRSKI
   pledge functionality - and once a domain certificate is enrolled they
   automatically enable ACP.

   Attempts for BRSKI pledge operations in greenfield state should
   terminate automatically when another method of configuring the node
   is used.  Methods that indicate some form of physical possession of
   the device such as configuration via the serial console could lead to
   immediate termination of BRSKI, while other parallel
   autoconfiguration auto
   configuration methods subject to remote attacks might lead to BRSKI
   termination only after they were successful.  Details of this may
   vary widely over different type of nodes.  When BRSKI pledge
   operation terminates, this will automatically unset "ANI enable" and
   should terminate any temporarily needed state on the device to
   perform BRSKI - DULL GRASP, BRSKI pledge and any IPv6 configuration
   on interfaces.

10.3.6.

10.5.6.  Undoing ANI/ACP enable

   Disabling ANI/ACP by undoing "ACP/ANI enable" is a risk for the
   reliable operations of the ACP if it can be executed by mistake or
   unauthorized.  This behavior could be influenced through some
   additional property in the certificate (e.g.: (e.g., in the domain
   information extension field) subject to future work: In an ANI
   deployment intended for convenience, disabling it could be allowed
   without further constraints.  In an ANI deployment considered to be
   critical more checks would be required.  One very controlled option
   would be to not permit these commands unless the domain certificate
   has been revoked or is denied renewal.  Configuring this option would
   be a parameter on the BRSKI registrar(s).  As long as the node did
   not receive a domain certificate, undoing "ANI/ACP enable" should not
   have any additional constraints.

10.3.7.

10.5.7.  Summary

   Node-wide "ACP/ANI enable [up-if-only]" commands enable the operation
   of ACP/ANI.  This is only auto-enabled on ANI greenfield devices,
   otherwise it must be configured explicitly.

   If the option "up-if-only" is not selected, interfaces enabled for
   ACP/ANI interpret "down" state as "admin down" and not "physical
   down".  In "admin-down" all non-ACP/ANI packets are filtered, but the
   physical layer is kept running to permit ACP/ANI to operate.

   (New) commands that result in physical interruption ("physical down",
   "loopback)
   "loopback") of ACP/ANI enabled interfaces should be built to protect
   continuance or reestablishment of ACP as much as possible.

   Interface level "ACP/ANI enable" control per-interface operations.
   It is enabled by default on native interfaces and has to be
   configured explicitly on other interfaces.

   Disabling "ACP/ANI enable" global and per-interface should have
   additional checks to minimize undesired breakage of ACP.  The degree
   of control could be a domain wide parameter in the domain
   certificates.

10.4.

10.6.  ACP Neighbor discovery protocol selection

   This section discusses why GRASP DULL was chosen as the discovery
   protocol for L2 adjacent candidate ACP neighbors.  The contenders
   considered where GRASP, mDNS or LLDP.

10.4.1.

10.6.1.  LLDP

   LLDP (and and Cisco's similar CDP) earlier Cisco Discovery Protocol (CDP) are example
   of L2 discovery protocols that terminate their messages on L2 ports.
   If those protocols would be chosen for ACP neighbor discovery, ACP
   neighbor discovery would therefore also terminate on L2 ports.  This
   would prevent ACP construction over non-ACP capable but LLDP or CDP
   enabled L2 switches.  LLDP has extensions using different MAC
   addresses and this could have been an option for ACP discovery as
   well, but the additional required IEEE standardization and definition
   of a profile for such a modified instance of LLDP seemed to be more
   work than the benefit of "reusing the existing protocol" LLDP for
   this very simple purpose.

10.4.2.

10.6.2.  mDNS and L2 support

   mDNS

   Multicast DNNS (mDNS) [RFC6762] with DNS-SD RRs (Resource Records) DNS Service Discovery (DNS-SD)
   Resource Records (RRs) as defined in [RFC6763] is a key contender as
   an ACP discovery protocol. because it relies on link-local IP
   multicast, it does operates at the subnet level, and is also found in
   L2 switches.  The authors of this document are not aware of mDNS
   implementation that terminate their mDNS messages on L2 ports instead
   of the subnet level.  If mDNS was used as the ACP discovery mechanism
   on an ACP capable (L3)/L2 switch as outlined in Section 7, then this
   would be necessary to implement.  It is likely that termination of
   mDNS messages could only be applied to all mDNS messages from such a
   port, which would then make it necessary to software forward any non-ACP non-
   ACP related mDNS messages to maintain prior non-ACP mDNS
   functionality.  Adding support for ACP into such L2 switches with
   mDNS could therefore create regression problems for prior mDNS
   functionality on those nodes.  With low performance of software
   forwarding in many L2 switches, this could also make the ACP risky to
   support on such L2 switches.

10.4.3.

10.6.3.  Why DULL GRASP

   LLDP was not considered because of the above mentioned issues. mDNS
   was not selected because of the above L2 mDNS considerations and
   because of the following additional points:

   If mDNS was not already existing in a node, it would be more work to
   implement than DULL GRASP, and if an existing implementation of mDNS
   was used, it would likely be more code space than a separate
   implementation of DULL GRASP or a shared implementation of DULL GRASP
   and GRASP in the ACP.

10.5.

10.7.  Choice of routing protocol (RPL)

   This Appendix explains section motivates why RPL - "IPv6 Routing Protocol for Low-Power
   and Lossy Networks ([RFC6550] was chosen as the default (and in this
   specification only) routing protocol for the ACP.  The choice and
   above explained profile was derived from a pre-standard
   implementation of ACP that was successfully deployed in operational
   networks.

   Requirements for routing in the ACP are:

   o  Self-management: The ACP must build automatically, without human
      intervention.  Therefore routing protocol must also work
      completely automatically.  RPL is a simple, self-managing
      protocol, which does not require zones or areas; it is also self-
      configuring, since configuration is carried as part of the
      protocol (see Section 6.7.6 of [RFC6550]).

   o  Scale: The ACP builds over an entire domain, which could be a
      large enterprise or service provider network.  The routing
      protocol must therefore support domains of 100,000 nodes or more,
      ideally without the need for zoning or separation into areas.  RPL
      has this scale property.  This is based on extensive use of
      default routing.  RPL also has other scalability improvements,
      such as selecting only a subset of peers instead of all possible
      ones, and trickle support for information synchronization.

   o  Low resource consumption: The ACP supports traditional network
      infrastructure, thus runs in addition to traditional protocols.
      The ACP, and specifically the routing protocol must have low
      resource consumption both in terms of memory and CPU requirements.
      Specifically, at edge nodes, where memory and CPU are scarce,
      consumption should be minimal.  RPL builds a destination-oriented
      directed acyclic graph (DODAG), where the main resource
      consumption is at the root of the DODAG.  The closer to the edge
      of the network, the less state needs to be maintained.  This
      adapts nicely to the typical network design.  Also, all changes
      below a common parent node are kept below that parent node.

   o  Support for unstructured address space: In the Autonomic
      Networking Infrastructure, node addresses are identifiers, and may
      not be assigned in a topological way.  Also, nodes may move
      topologically, without changing their address.  Therefore, the
      routing protocol must support completely unstructured address
      space.  RPL is specifically made for mobile ad-hoc networks, with
      no assumptions on topologically aligned addressing.

   o  Modularity: To keep the initial implementation small, yet allow
      later for more complex methods, it is highly desirable that the
      routing protocol has is highly desirable that the
      routing protocol has a simple base functionality, but can import
      new functional modules if needed.  RPL has this property with the
      concept of "objective function", which is a plugin to modify
      routing behavior.

   o  Extensibility: Since the Autonomic Networking Infrastructure is a
      new concept, it is likely that changes in the way of operation
      will happen over time.  RPL allows for new objective functions to
      be introduced later, which allow changes to the way the routing
      protocol creates the DAGs.

   o  Multi-topology support: It may become necessary in the future to
      support more than one DODAG for different purposes, using
      different objective functions.  RPL allow for the creation of
      several parallel DODAGs, should this be required.  This could be
      used to create different topologies to reach different roots.

   o  No need for path optimization: RPL does not necessarily compute
      the optimal path between any two nodes.  However, the ACP does not
      require this today, since it carries mainly non-delay-sensitive
      feedback loops.  It is possible that different optimization
      schemes become necessary in the future, but RPL can be expanded
      (see point "Extensibility" above).

10.8.  ACP Information Distribution and multicast

   IP multicast is not used by the ACP because the ANI (Autonomic
   Networking Infrastructure) itself does not require IP multicast but
   only service announcement/discovery.  Using IP multicast for that
   would have made it necessary to develop a zero-touch auto configuring
   solution for ASM (Any Source Multicast - the original form of IP
   multicast defined in [RFC1112]), which would be quite complex and
   difficult to justify.  One aspect of complexity where no attempt at a
   solution has been described in IETF documents is the automatic-
   selection of routers that should be PIM Sparse Mode (PIM-SM)
   Rendezvous Points (RPs) (see [RFC7761]).  The other aspects of
   complexity are the implementation of MLD ([RFC4604]), PIM-SM and
   Anycast-RP (see [RFC4610]).  If those implementations already exist
   in a product, then they would be very likely tied to accelerated
   forwarding which consumes hardware resources, and that in return is
   difficult to justify as a cost of performing only service discovery.

   Some future ASA may need high performance in-network data
   replication.  That is the case when the use of IP multicast is
   justified.  Such an ASA can then use service discovery from ACP
   GRASP, and then they do not need ASM but only SSM (Source Specific
   Multicast, see [RFC4607]) for the IP multicast replication.  SSM
   itself can simply be enabled in the Data-Plane (or even in an update
   to the ACP) without any other configuration than just enabling it on
   all nodes and only requires a simple base functionality, but can import
      new functional modules if needed.  RPL has this property with the
      concept simpler version of "objective function", which is MLD (see [RFC5790]).

   LSP (Link State Protocol) based IGP routing protocols typically have
   a plugin mechanism to modify flood information, and such a mechanism could be used
   to flood GRASP objectives by defining them to be information of that
   IGP.  This would be a possible optimization in future variations of
   the ACP that do use an LSP routing behavior.

   o  Extensibility: Since protocol.  Note though that such a
   mechanism would not work easily for GRASP M_DISCOVERY messages which
   are intelligently (constrained) flooded not across the Autonomic Networking Infrastructure is whole ACP, but
   only up to a
      new concept, it node where a responder is likely found.  We do expect that changes many
   future services in the way of operation ASA will happen over time.  RPL allows have only few consuming ASA, and for new objective functions to
      be introduced later, which allow changes to the way
   those cases, M_DISCOVERY is the routing
      protocol creates more efficient method than flooding
   across the DAGs.

   o  Multi-topology support: It may become necessary in whole domain.

   Because the ACP uses RPL, one desirable future extension is to
      support use
   RPLs existing notion of loop-free distribution trees (DODAG) to make
   GRASPs flooding more than one DODAG for different purposes, using
      different objective functions.  RPL allow efficient both for the creation of
      several parallel DODAGs, should M_FLOOD and M_DISCOVERY) See
   Section 6.12.5 how this will be required. specifically beneficial when using
   NBMA interfaces.  This could be
      used to create different topologies to reach different roots.

   o  No need for path optimisation: RPL does not necessarily compute
      the optimal path between any two nodes.  However, the ACP does is not
      require currently specified in this today, since document
   because it carries mainly non-delay-sensitive
      feedback loops.  It is possible that different optimisation
      schemes become necessary in not quite clear yet what exactly the future, but implications are
   to make GRASP flooding depend on RPL can DODAG convergence and how
   difficult it would be expanded
      (see point "Extensibility" above).

10.6. to let GRASP flooding access the DODAG
   information.

10.9.  Extending ACP channel negotiation (via GRASP)

   The mechanism described in the normative part of this document to
   support multiple different ACP secure channel protocols without a
   single network wide MTI protocol is important to allow extending
   secure ACP channel protocols beyond what is specified in this
   document, but it will run into problem if it would be used for
   multiple protocols:

   The need to potentially have multiple of these security associations
   even temporarily run in parallel to determine which of them works
   best does not support the most lightweight implementation options.

   The simple policy of letting one side (Alice) decide what is best may
   not lead to the mutual best result.

   The two limitations can easier be solved if the solution was more
   modular and as few as possible initial secure channel negotiation
   protocols would be used, and these protocols would then take on the
   responsibility to support more flexible objectives to negotiate the
   mutually preferred ACP security channel protocol.

   IKEv2 is the IETF standard protocol to negotiate network security
   associations.  It is meant to be extensible, but it is unclear
   whether it would be feasible to extend IKEv2 to support possible
   future requirements for ACP secure channel negotiation:

   Consider the simple case where the use of native IPsec vs. IPsec via
   GRE is to be negotiated and the objective is the maximum throughput.
   Both sides would indicate some agreed upon performance metric and the
   preferred encapsulation is the one with the higher performance of the
   slower side.  IKEv2 does not support negotiation with this objective.

   Consider dTLS DTLS and some form of 802.1AE ([MACSEC]) MacSec are to be added as negotiation
   options - and the performance objective should work across all IPsec,
   dDTLS and 802.1AE MacSec options.  In the case of MacSEC, the negotiation
   would also need to determine a key for the peering.  It is unclear if
   it would be even appropriate to consider extending the scope of
   negotiation in IKEv2 to those cases.  Even if feasible to define, it
   is unclear if implementations of IKEv2 would be eager to adopt those
   type of extension given the long cycles of security testing that
   necessarily goes along with core security protocols such as IKEv2
   implementations.

   A more modular alternative to extending IKEv2 could be to layer a
   modular negotiation mechanism on top of the multitude of existing or
   possible future secure channel protocols.  For this, GRASP over TLS
   could be considered as a first ACP secure channel negotiation
   protocol.  The following are initial considerations for such an
   approach.  A full specification is subject to a separate document:

   To explicitly allow negotiation of the ACP channel protocol, GRASP
   over a TLS connection using the GRASP_LISTEN_PORT and the nodes and
   peers link-local IPv6 address is used.  When Alice and Bob support
   GRASP negotiation, they do prefer it over any other non-explicitly
   negotiated security association protocol and should wait trying any
   non-negotiated ACP channel protocol until after it is clear that
   GRASP/TLS will not work to the peer.

   When Alice and Bob successfully establish the GRASP/TSL session, they
   will negotiate the channel mechanism to use using objectives such as
   performance and perceived quality of the security.  After agreeing on
   a channel mechanism, Alice and Bob start the selected Channel
   protocol.  Once the secure channel protocol is successfully running,
   the GRASP/TLS connection can be kept alive or timed out as long as
   the selected channel protocol has a secure association between Alice
   and Bob.  When it terminates, it needs to be re-negotiated via GRASP/
   TLS.

   Notes:

   o  Negotiation of a channel type may require IANA assignments of code
      points.

   o  TLS is subject to reset attacks, which IKEv2 is not.  Normally,
      ACP connections (as specified in this document) will be over link-
      local addresses so the attack surface for this one issue in TCP
      should be reduced (note that this may not be true when ACP is
      tunneled as described in Section 8.2.2.

   o  GRASP packets received inside a TLS connection established for
      GRASP/TLS ACP negotiation are assigned to a separate GRASP domain
      unique to that TLS connection.

10.7.

10.10.  CAs, domains and routing subdomains

   There is a wide range of setting up different ACP solution by
   appropriately using CAs and the domain and rsub elements in the
   domain information field of the domain certificate.  We summarize
   these options here as they have been explained in different parts of
   the document in before and discuss possible and desirable extensions:

   An ACP domain is the set of all ACP nodes using certificates from the
   same CA using the same domain field.  GRASP inside the ACP is run
   across all transitively connected ACP nodes in a domain.

   The rsub element in the domain information field primarily allows to permits the use of
   addresses from different ULA prefixes.  One use case is to create
   multiple networks that initially may be separated, but where it
   should be possible to connect them without further extensions to ACP
   when necessary.

   Another use case for routing subdomains is as the starting point for
   structuring routing inside an ACP.  For example, different routing
   subdomains could run different routing protocols or different
   instances of RPL and auto-aggregation / distribution of routes could
   be done across inter routing subdomain ACP channels based on
   negotiation (e.g.: (e.g., via GRASP).  This is subject for further work.

   RPL scales very well.  It is not necessary to use multiple routing
   subdomains to scale ACP domains in a way it would be possible if
   other routing protocols where used.  They exist only as options for
   the above mentioned reasons.

   If different ACP domains are to be created that should not allow to
   connect to each other by default, these ACP domains simply need to
   have different domain elements in the domain information field.
   These domain elements can be arbitrary, including subdomains of one
   another: Domains "example.com" and "research.example.com" are
   separate domains if both are domain elements in the domain
   information element of certificates.

   It is not necessary to have a separate CA for different ACP domains:
   an operator can use a single CA to sign certificates for multiple ACP
   domains that are not allowed to connect to each other because the
   checks for ACP adjacencies includes comparison of the domain part.

   If multiple independent networks choose the same domain name but had
   their own CA, these would not form a single ACP domain because of CA
   mismatch.  Therefore there is no problem in choosing domain names
   that are potentially also used by others.  Nevertheless it is highly
   recommended to use domain names that one can have high probability to
   be unique.  It is recommended to use domain names that start with a
   DNS domain names owned by the assigning organization and unique
   within it.  For example "acp.example.com" if you own "example.com".

   Future extensions, primarily through intent can create more flexible
   options how to build ACP domains.

   Intent could modify the ACP connection check to permit connections
   between different domains.

   If different domains use the same CA one would change the ACP setup
   to permit for the ACP to be established between the two ACP nodes,
   but no routing nor ACP GRASP to be built across this adjacency.  The
   main difference over routing subdomains is to not permit for the ACP
   GRASP instance to be built across the adjacency.  Instead, one would
   only build a point to point GRASP instance between those peers to
   negotiate what type of exchanges are desired across that connection.
   This would include routing negotiation, how much GRASP information to
   transit and what data-plane Data-Plane forwarding should be done.  This approach
   could also allow for Intent to only be injected into the network from
   one side and propagate via this GRASP connection.

   If different domains have different CAs, they should start to trust
   each other by intent injected into both domains that would add the
   other domains CA as a trust point during the ACP connection setup -
   and then following up with the previous point of inter-domain
   connections across domains with the same CA (e.g.: (e.g., GRASP
   negotiation).

10.8.

10.11.  Adopting ACP concepts for other environments

   The ACP as specified in this document is very explicit about the
   choice of options to allow interoperable implementations.  The
   choices made may not be the best for all environments, but the
   concepts used by the ACP can be used to build derived solutions:

   The ACP specifies the use of ULA and deriving its prefix from the
   domain name so that no address allocation is required to deploy the
   ACP.  The ACP will equally work not using ULA but any other /50 IPv6
   prefix.  This prefix could simply be a configuration of the ACP
   registrars (for example when using BRSKI BRSKI) to enroll the domain
   certificates - instead of the ACP registrar deriving the /50 ULA
   prefix from the AN domain name.

   Some solutions may already have an auto-addressing scheme, for
   example derived from existing unique device identifiers (e.g.: (e.g., MAC
   addresses).  In those cases it may not be desirable to assign
   addresses to devices via the ACP address information field in the way
   described in this document.  The certificate may simply serve to
   identify the ACP domain, and the address field could be empty/unused.
   The only fix required in the remaining way the ACP operate is to
   define another element in the domain certificate for the two peers to
   decide who is Alice and who is Bob during secure channel building.
   Note though that future work may leverage the acp address to
   authenticate "ownership" of the address by the device.  If the
   address used by a device is derived from some pre-existing permanent
   local ID (such as MAC address), then it would be useful to store that
   address in the certificate using the format of the access address
   information field or in a similar way.

   The ACP is defined as a separate VRF because it intends to support
   well managed networks with a wide variety of configurations.
   Therefore, reliable, configuration-indestructible connectivity cannot
   be achieved from the data-plane Data-Plane itself.  In solutions where all
   transit connectivity impacting functions are fully automated
   (including security), indestructible and resilient, it would be
   possible to eliminate the need for the ACP to be a separate VRF.
   Consider the most simple example system in which there is no separate
   data-plane,
   Data-Plane, but the ACP is the data-plane. Data-Plane.  Add BRSKI, and it becomes
   a fully autonomic network - except that it does not support automatic
   addressing for user equipment.  This gap can then be closed for
   example by adding a solution derived from
   [I-D.ietf-anima-prefix-management].

   TCP/TLS as the protocols to provide reliability and security to GRASP
   in the ACP may not be the preferred choice in constrained networks.
   For example, CoAP/DTLS (Constrained Application Protocol) may be
   preferred where they are already used, allowing to reduce the
   additional code space footprint for the ACP on those devices.
   Because the transport for GRASP is not only hop-by-hop, but end-to-
   end across the ACP, this would require the definition of an
   incompatible variant of the ACP.  Non-constrained devices could
   support both variants (the ACP as defined here, and one using CoAP/
   DTLS for GRASP), and the variant used in a deployment could be chosen
   for example through a parameter of the domain certificate.

   The routing protocol chosen by the ACP design (RPL) does explicitly
   not optimize for shortest paths and fastest convergence.  Variations
   of the ACP may want to use a different routing protocol. protocol or introduce
   more advanced RPL profiles.

   Variations such as what routing protocol to use, or whether to
   instantiate an ACP in a VRF or (as suggested above) as the actual
   data-plane,
   Data-Plane, can be automatically chosen in implementations built to
   support multiple options by deriving them from future parameters in
   the certificate.  Parameters in certificates should be limited to
   those that would not need to be changed more often than certificates
   would need to be updated anyhow; Or by ensuring that these parameters
   can be provisioned before the variation of an ACP is activated in a
   node.  Using BRSKI, this could be done for example as additional
   follow-up signaling directly after the certificate enrolment, enrollment, still
   leveraging the BRSKI TLS connection and therefore not introducing any
   additional connectivity requirements.

   Last but not least, secure channel protocols including their
   encapsulation are easily added to ACP solutions.  Secure channels may
   even be replaced by simple neighbor authentication to create
   simplified ACP variations for environments where no real security is
   required but just protection against non-malicious misconfiguration.
   Or for environments where all traffic is known or forced to be end-
   to-end protected and other means for infrastructure protection are
   used.  Any future network OAM should always use end-to-end security
   anyhow and can leverage the domain certificates and is therefore not
   dependent on security to be provided for by ACP secure channels.

11.  Security Considerations

   An ACP is self-protecting and there is no need to apply configuration
   to make it secure.  Its security therefore does not depend on
   configuration.

   However, the security of the ACP depends on a number of other
   factors:

   o  The usage of domain certificates depends on a valid supporting PKI
      infrastructure.  If the chain of trust of this PKI infrastructure
      is compromised, the security of the ACP is also compromised.  This
      is typically under the control of the network administrator.

   o  Security can be compromised by implementation errors (bugs), as in
      all products.

   There is no prevention of source-address spoofing inside the ACP.
   This implies that if an attacker gains access to the ACP, it can
   spoof all addresses inside the ACP and fake messages from any other
   node.

   Fundamentally, security depends on correct operation, implementation
   and architecture.  Autonomic approaches such as the ACP largely
   eliminate the dependency on correct operation; implementation and
   architectural mistakes are still possible, as in all networking
   technologies.

   Many details of ACP are designed with security in mind and discussed
   elsewhere in the document:

   IPv6 addresses used by nodes in the ACP are covered as part of the
   nodes domain certificate as described in Section 6.1.1.  This allows
   even verification of ownership of a peers IPv6 address when using a
   connection authenticated with the domain certificate.

   The ACP acts as a security (and transport) substrate for GRASP inside
   the ACP such that GRASP is not only protected by attacks from the
   outside, but also by attacks from compromised inside attackers - by
   relying not only on hop-by-hop security of ACP secure channels, but
   adding end-to-end security for those GRASP messages.  See
   Section 6.8.2.

   ACP provides for secure, resilient zero-touch discovery of EST
   servers for certificate renewal.  See Section 6.1.3.

   ACP provides extensible, auto-configuring hop-by-hop protection of
   the ACP infrastructure via the negotiation of hop-by-hop secure
   channel protocols.  See Section 6.5 and Section 10.6. 10.9.

   The ACP is designed to minimize attacks from the outside by
   minimizing its dependency against any non-ACP operations on a node.
   The only dependency in the specification in this document is the need
   to share link-local addresses for the ACP secure channel
   encapsulation with the data-plane. Data-Plane.  See Section 6.12.2.

   In combination with BRSKI, ACP enables a resilient, fully zero-touch
   network solution for short-lived certificates that can be renewed or
   re-enrolled even after unintentional expiry (e.g.: (e.g., because of
   interrupted connectivity).  See Section 10.1.

12.  IANA Considerations

   This document defines the "Autonomic Control Plane".

   The IANA is requested to register the value "AN_ACP" (without quotes)
   to the GRASP Objectives Names Table in the GRASP Parameter Registry.
   The specification for this value is this document, Section 6.3.

   The IANA is requested to register the value "SRV.est" (without
   quotes) to the GRASP Objectives Names Table in the GRASP Parameter
   Registry.  The specification for this value is this document,
   Section 6.1.3.

   Note that the objective format "SRV.<service-name>" is intended to be
   used for any <service-name> that is an [RFC6335] registered service
   name.  This is a proposed update to the GRASP registry subject to
   future work and only mentioned here for informational purposed to
   explain the unique format of the objective name.

   The IANA is requested to create an ACP Parameter Registry with
   currently one registry table - to
   explain the "ACP Address Type" table. unique format of the objective name.

   The IANA is requested to create an ACP Parameter Registry with
   currently one registry table - the "ACP Address Type" table.

   "ACP Address Type" Table.  The value in this table are numeric values
   0...3 paired with a name (string).  Future values MUST be assigned
   using the Standards Action policy defined by [RFC8126].  The
   following initial values are assigned by this document:

   0: ACP Zone Addressing Sub-Scheme (ACP RFC Figure 4) 9) / ACP Manual
   Addressing Sub-Scheme (ACP RFC Section 6.10.4)
   1: ACP Vlong Addressing Sub-Scheme (ACP RFC Section 6.10.5)

13.  Acknowledgements

   This work originated from an Autonomic Networking project at Cisco
   Systems, which started in early 2010.  Many people contributed to
   this project and the idea of the Autonomic Control Plane, amongst
   which (in alphabetical order): Ignas Bagdonas, Parag Bhide, Balaji
   BL, Alex Clemm, Yves Hertoghs, Bruno Klauser, Max Pritikin, Michael
   Richardson, Ravi Kumar Vadapalli.

   Special thanks to Brian Carpenter Carpenter, Elwyn Davies, Joel Halpern and
   Sheng Jiang for their thorough reviews and to Pascal Thubert and
   Michael Richardson to provide the details for the recommendations of
   the use of RPL in the ACP ACP.

   Further input, review or suggestions were received from: Rene Struik,
   Brian Carpenter, Benoit Claise, William Atwood and Yongkang Zhang.

14.  Change log [RFC Editor: Please remove]

14.1.  Initial version

   First version of this document: draft-behringer-autonomic-control-
   plane

14.2.  draft-behringer-anima-autonomic-control-plane-00

   Initial version of the anima document; only minor edits.

14.3.  draft-behringer-anima-autonomic-control-plane-01

   o  Clarified that the ACP should be based on, and support only IPv6.

   o  Clarified in intro that ACP is for both, between devices, as well
      as for access from a central entity, such as an NMS.

   o  Added a section on how to connect an NMS system.

   o  Clarified the hop-by-hop crypto nature of the ACP.

   o  Added several references to GDNP as a candidate protocol.

   o  Added a discussion on network split and merge.  Although, this
      should probably go into the certificate management story longer
      term.

14.4.  draft-behringer-anima-autonomic-control-plane-02

   Addresses (numerous) comments from Brian Carpenter.  See mailing list
   for details.  The most important changes are:

   o  Introduced a new section "overview", to ease the understanding of
      the approach.

   o  Merged the previous "problem statement" and "use case" sections
      into a mostly re-written "use cases" section, since they were
      overlapping.

   o  Clarified the relationship with draft-ietf-anima-stable-
      connectivity

14.5.  draft-behringer-anima-autonomic-control-plane-03

   o  Took out requirement for IPv6 --> that's in the reference doc.

   o  Added requirement section.

   o  Changed focus: more focus on autonomic functions, not only virtual
      out of band.
      out-of-band.  This goes a bit throughout the document, starting
      with a changed abstract and intro.

14.6.  draft-ietf-anima-autonomic-control-plane-00

   No changes; re-submitted as WG document.

14.7.  draft-ietf-anima-autonomic-control-plane-01

   o  Added some paragraphs in addressing section on "why IPv6 only", to
      reflect the discussion on the list.

   o  Moved the data-plane Data-Plane ACP out of the main document, into an
      appendix.  The focus is now the virtually separated ACP, since it
      has significant advantages, and isn't much harder to do.

   o  Changed the self-creation algorithm: Part of the initial steps go
      into the reference document.  This document now assumes an
      adjacency table, and domain certificate.  How those get onto the
      device is outside scope for this document.

   o  Created a new section 6 "workarounds for non-autonomic nodes", and
      put the previous controller section (5.9) into this new section.
      Now, section 5 is "autonomic only", and section 6 explains what to
      do with non-autonomic stuff.  Much cleaner now.

   o  Added an appendix explaining the choice of RPL as a routing
      protocol.

   o  Formalised the creation process a bit more.  Now, we create a
      "candidate peer list" from the adjacency table, and form the ACP
      with those candidates.  Also it explains now better that policy
      (Intent) can influence the peer selection. (section 4 and 5)

   o  Introduce a section for the capability negotiation protocol
      (section 7).  This needs to be worked out in more detail.  This
      will likely be based on GRASP.

   o  Introduce a new parameter: ACP tunnel type.  And defines it in the
      IANA considerations section.  Suggest GRE protected with IPSec
      transport mode as the default tunnel type.

   o  Updated links, lots of small edits.

14.8.  draft-ietf-anima-autonomic-control-plane-02

   o  Added explicitly text for the ACP channel negotiation.

   o  Merged draft-behringer-anima-autonomic-addressing-02 into this
      document, as suggested by WG chairs.

14.9.  draft-ietf-anima-autonomic-control-plane-03

   o  Changed Neighbor discovery protocol from GRASP to mDNS.  Bootstrap
      protocol team decided to go with mDNS to discover bootstrap proxy,
      and ACP should be consistent with this.  Reasons to go with mDNS
      in bootstrap were a) Bootstrap should be reuseable also outside of
      full anima solutions and introduce as few as possible new
      elements. mDNS was considered well-known and very-likely even pre-
      existing in low-end devices (IoT). b) Using GRASP both for the
      insecure neighbor discovery and secure ACP operatations raises the
      risk of introducing security issues through implementation issues/
      non-isolation between those two instances of GRASP.

   o  Shortened the section on GRASP instances, because with mDNS being
      used for discovery, there is no insecure GRASP session any longer,
      simplifying the GRASP considerations.

   o  Added certificate requirements for ANIMA in section 5.1.1,
      specifically how the ANIMA information is encoded in
      subjectAltName.

   o  Deleted the appendix on "ACP without separation", as originally
      planned, and the paragraph in the main text referring to it.

   o  Deleted one sub-addressing scheme, focusing on a single scheme
      now.

   o  Included information on how ANIMA information must be encoded in
      the domain certificate in section "preconditions".

   o  Editorial changes, updated draft references, etc.

14.10.  draft-ietf-anima-autonomic-control-plane-04

   Changed discovery of ACP neighbor back from mDNS to GRASP after
   revisiting the L2 problem.  Described problem in discovery section
   itself to justify.  Added text to explain how ACP discovery relates
   to BRSKY (bootstrap) discovery and pointed to Michael Richardsons
   draft detailing it.  Removed appendix section that contained the
   original explanations why GRASP would be useful (current text is
   meant to be better).

14.11.  draft-ietf-anima-autonomic-control-plane-05

   o  Section 5.3 (candidate ACP neighbor selection): Add that Intent
      can override only AFTER an initial default ACP establishment.

   o  Section 6.10.1 (addressing): State that addresses in the ACP are
      permanent, and do not support temporary addresses as defined in
      RFC4941.
      RFC4941.

   o  Modified Section 6.3 to point to the GRASP objective defined in
      draft-carpenter-anima-ani-objectives. (and added that reference)

   o  Section 6.10.2: changed from MD5 for calculating the first 40 bits
      to SHA256; reason is MD5 should not be used any more.

   o  Added address sub-scheme to the IANA section.

   o  Made the routing section more prescriptive.

   o  Clarified in Section 8.1.1 the ACP Connect port, and defined that
      term "ACP Connect".

   o  Section 8.2: Added some thoughts (from mcr) on how traversing a L3
      cloud could be automated.

   o  Added a CRL check in Section 6.7.

   o  Added a note on the possibility of source-address spoofing into
      the security considerations section.

   o  Other editoral changes, including those proposed by Michael
      Richardson on 30 Nov 2016 (see ANIMA list).

14.12.  draft-ietf-anima-autonomic-control-plane-06

   o  Added proposed RPL profile.

   o  detailed DTLS profile - DTLS with any additional negotiation/
      signaling channel.

   o  Fixed up text for ACP/GRE encap.  Removed text claiming its
      incompatible with non-GRE IPsec and detailled it.

   o  Added text to suggest admin down interfaces should still run ACP.

14.13.  draft-ietf-anima-autonomic-control-plane-07

   o  Changed author association.

   o  Improved ACP connect setion (after confusion about term came up in
      the stable connectivity draft review).  Added picture, defined
      complete terminology.

   o  Moved ACP channel negotiation from normative section to appendix
      because it can in the timeline of this document not be fully
      specified to be implementable.  Aka: work for future document.
      That work would also need to include analysing IKEv2 and describin
      the difference of a proposed GRASP/TLS solution to it.

   o  Removed IANA request to allocate registry for GRASP/TLS.  This
      would come with future draft (see above).

   o  Gave the name "ACP information field" to the field in the
      certificate carrying the ACP address and domain name.

   o  Changed the rules for mutual authentication of certificates to
      rely on the domain in the ACP information field of the certificate
      instead of the OU in the certificate.  Also renewed the text
      pointing out that the ACP information field in the certificate is
      meant to be in a form that it does not disturb other uses of the
      certificate.  As long as the ACP expected to rely on a common OU
      across all certificates in a domain, this was not really true:
      Other uses of the certificates might require different OUs for
      different areas/type of devices.  With the rules in this draft
      version, the ACP authentication does not rely on any other fields
      in the certificate.

   o  Added an extension field to the ACP information field so that in
      the future additional fields like a subdomain could be inserted.
      An example using such a subdomain field was added to the pre-
      existing text suggesting sub-domains.  This approach is necessary
      so that there can be a single (main) domain in the ACP information
      field, because that is used for mutual authentication of the
      certificate.  Also clarified that only the register(s) SHOULD/MUST
      use that the ACP address was generated from the domain name - so
      that we can easier extend change this in extensions.

   o  Modified Section 6.3 to point to  Took the text for the GRASP objective defined in
      draft-carpenter-anima-ani-objectives. (and added that reference)

   o  Section 6.10.2: changed discovery of ACP neighbors from MD5 for calculating Brians
      grasp-ani-objectives draft.  Alas, that draft was behind the first 40 bits
      latest GRASP draft, so i had to SHA256; reason overhaul.  The mayor change is MD5 should to
      describe in the ACP draft the whole format of the M_FLOOD message
      (and not be used any more.

   o  Added address sub-scheme only the actual objective).  This should make it a lot
      easier to read (without having to go back and forth to the IANA section.

   o  Made GRASP
      RFC/draft).  It was also necessary because the routing section more prescriptive.

   o  Clarified locator in Section 8.1.1 the ACP Connect port,
      M_FLOOD messages has an important role and defined that
      term "ACP Connect".

   o  Section 8.2: Added some thoughts (from mcr) on its not coded inside
      the objective.  The specification of how traversing a L3
      cloud could to format the M_FLOOD
      message shuold now be automated.

   o  Added a CRL check complete, the text may be some duplicate
      with the DULL specificateion in Section 6.7. GRASP, but no contradiction.

   o  Added a note on  One of the possibility main outcomes of source-address spoofing into reworking the GRASP section was the
      notion that GRASP announces both the candidate peers IPv6 link
      local address but also the support ACP security considerations section.

   o  Other editoral changes, protocol including those proposed
      the port it is running on.  In the past we shied away from using
      this information because it is not secured, but i think the
      additional attack vectors possible by Michael
      Richardson using this information are
      negligible: If an attacker on 30 Nov 2016 (see ANIMA list).

14.12.  draft-ietf-anima-autonomic-control-plane-06

   o  Added proposed RPL profile.

   o  detailed dTLS profile - dTLS with any additional negotiation/
      signaling channel. an L2 subnet can fake another
      devices GRASP message then it can already provide a similar amount
      of attack by purely faking the link-local address.

   o  Fixed up text for ACP/GRE encap.  Removed text claiming its
      incompatible with non-GRE IPsec and detailled it.

   o  Added text to suggest admin down interfaces should still run ACP.

14.13.  draft-ietf-anima-autonomic-control-plane-07

   o  Changed author association.

   o  Improved ACP connect setion (after confusion about term came up in the stable connectivity draft review).  Added picture, defined
      complete terminology.

   o  Moved ACP channel negotiation from normative section to appendix
      because it on discovery and BRSKI.  This can be revived
      in the timeline of this BRSKI document, but it seems mood given how we did remove
      mDNS from the latest BRSKI document (aka: this section discussed
      discrepancies between GRASP and mDNS discovery which should not be fully
      specified to be implementable.  Aka: work for future document.
      That work would also need
      exist anymore with latest BRSKI.

   o  Tried to include analysing IKEv2 and describin resolve the difference of a proposed GRASP/TLS solution to it.

   o  Removed IANA request EDNOTE about CRL vs. OCSP by pointing out we
      do not specify which one is to allocate registry for GRASP/TLS.  This
      would come with future draft (see above).

   o  Gave be used but that the name "ACP information field" ACP should be
      used to reach the field URL included in the certificate carrying to get to the ACP address and domain name.
      CRL storage or OCSP server.

   o  Changed the rules for mutual authentication of certificates ACP via IPsec to
      rely on the domain in ACP via IKEv2 and restructured the
      sections to make IPsec native and IPsec via GRE subsections.

   o  No need for any assigned DTLS port if ACP information field is run across DTLS
      because it is signaled via GRASP.

14.14.  draft-ietf-anima-autonomic-control-plane-08

   Modified mentioning of the certificate
      instead BRSKI to make it consistent with current
   (07/2017) target for BRSKI: MASA and IDevID are mandatory.  Devices
   with only insecure UDI would need a security reduced variant of the OU in the certificate.
   BRSKI.  Also renewed the text
      pointing out that the added mentioning of Netconf Zero-Touch.  Made BRSKI non-
   normative for ACP information field in because wrt.  ACP it is just one option how the
   domain certificate can be provisioned.  Instead, BRSKI is
      meant mandatory
   when a device implements ANI which is ACP+BRSKI.

   Enhanced text for ACP across tunnels to be in decribe two options: one
   across configured tunnels (GRE, IPinIP etc) a form more efficient one via
   directed DULL.

   Moved decription of BRSKI to appendex to emphasize that it does BRSKI is not disturb other uses
   a (normative) dependency of the
      certificate.  As long as the GRASP, enhanced text to indicate other
   options how Domain Certificates can be provisioned.

   Added terminology section.

   Separated references into normative and non-normative.

   Enhanced section about ACP expected via "tunnels".  Defined an option to rely on a common OU
      across all certificates in a domain, this was not really true:
      Other uses run
   ACP secure channel without an outer tunnel, discussed PMTU, benefits
   of the certificates might require different OUs for
      different areas/type tunneling, potential of devices.  With the rules in using this draft
      version, the with BRSKI, made ACP authentication does not rely via GREP a
   SHOULD requirement.

   Moved appendix sections up before IANA section because there where
   concerns about appendices to be to far on any other fields
      in the certificate.

   o bottom to be read.
   Added an extension field (Informative) / (Normative) to the section titles to clarify which
   sections are informative and which are normative

   Moved explanation of ACP information field so that with L2 from precondition to separate
   section before workarounds, made it instructive enough to explain how
   to implement ACP on L2 ports for L3/L2 switches and made this part of
   normative requirement (L2/L3 switches SHOULD support this).

   Rewrote section "GRASP in the future additional fields like a subdomain could be inserted.
      An example using such a subdomain field was added ACP" to the pre-
      existing text suggesting sub-domains.  This approach is necessary
      so that there can be a single (main) domain define GRASP in ACP as
   mandatory (and why), and define the ACP information
      field, because that as security and transport
   substrate to GRASP in ACP.  And how it works.

   Enhanced "self-protection" properties section: protect legacy
   management protocols.  Security in ACP is used for mutual authentication of the protection from outside
   and those legacy protocols.  Otherwise need end-to-end encryption
   also inside ACP, e.g., with domain certificate.  Also clarified that only

   Enhanced initial domain certificate section to include requirements
   for maintenance (renewal/revocation) of certificates.  Added
   explanation to BRSKI informative section how to handle very short
   lived certificates (renewal via BRSKI with expired cert).

   Modified the register(s) SHOULD/MUST
      use that encoding of the ACP address was generated from the domain name - so
      that we can easier extend change this to better fit RFC822 simple
   local-parts (":" as required by RFC5952 are not permitted in simple
   dot-atoms according to RFC5322.  Removed reference to RFC5952 as its
   now not needed anymore.

   Introduced a sub-domain field in extensions.

   o  Took the text for the GRASP discovery of ACP neighbors from Brians
      grasp-ani-objectives draft.  Alas, that draft was behind information in the
      latest GRASP draft, so i had
   certificate to overhaul.  The mayor change allow defining such subdomains with depending on
   future Intent definitions.  It also makes it clear what the "main
   domain" is.  Scheme is called "routing subdomain" to
      describe have a unique
   name.

   Added V8 (now called Vlong) addressing sub-scheme according to
   suggestion from mcr in his mail from 30 Nov 2016
   (https://mailarchive.ietf.org/arch/msg/anima/
   nZpEphrTqDCBdzsKMpaIn2gsIzI).  Also modified the ACP draft the whole format explanation of the M_FLOOD message
      (and not only
   single V bit in the actual objective).  This should make it a lot
      easier first sub-scheme now renamed to read (without having Zone sub-scheme
   to go back and forth distinguish it.

14.15.  draft-ietf-anima-autonomic-control-plane-09

   Added reference to the GRASP
      RFC/draft).  It was also necessary because the locator in the
      M_FLOOD messages has an important role RFC4191 and its not coded inside
      the objective.  The specification of explained how to format the M_FLOOD
      message shuold now be complete, the text may it should be some duplicate
      with the DULL specificateion in GRASP, but no contradiction.

   o  One used on ACP
   edge routers to allow auto configuration of the main outcomes routing by NMS hosts.
   This came after review of reworking the GRASP section stable connectivity draft where ACP connect
   is being referred to.

   V8 addressing Sub-Scheme was the
      notion that GRASP announces both the candidate peers IPv6 link modified to allow not only /8 device-
   local address space but also /16.  This was in response to the support
   possible need to have maybe as much as 2^12 local addresses for
   future encaps in BRSKI like IPinIP.  It also would allow fully
   autonomic address assignment for ACP security protocol including
      the port it is running on.  In the past we shied away connect interfaces from using
      this information because it is not secured, but i think the
      additional attack vectors possible by using this information are
      negligible: If an attacker on
   local address space (on an L2 subnet can fake another
      devices GRASP message then it can already provide a similar amount ACP edge device), subject to approval of attack by purely faking
   the link-local address. implied update to rfc4291/rfc4193 (IID length).  Changed name to
   Vlong addressing sub-scheme.

   Added text in response to Brian Carpenters review of draft-ietf-
   anima-stable-connectivity-04.

   o  Removed the section on discovery and BRSKI.  This can be revived  The stable connectivity draft was vaguely describing ACP connect
      behavior that is better standardized in the BRSKI document, but it seems mood given how we did remove
      mDNS from the latest BRSKI document (aka: this section discussed
      discrepancies between GRASP and mDNS discovery which should not
      exist anymore with latest BRSKI. ACP draft.

   o  Tried to resolve the EDNOTE about CRL vs. OCSP  Added new ACP "Manual" addressing sub-scheme with /64 subnets for
      use with ACP connect interfaces.  Being covered by pointing out we the ACP ULA
      prefix, these subnets do not specify which one is require additional routing entries
      for NMS hosts.  They also are fully 64-bit IID length compliant
      and therefore not subject to be used but 4191bis considerations.  And they
      avoid that operators manually assign prefixes from the ACP should ULA
      prefixes that might later be
      used to reach the URL included in the certificate to get to the
      CRL storage or OCSP server. assigned autonomiously.

   o  Changed  ACP via IPsec to connect auto-configuration: Defined that ACP via IKEv2 and restructured the
      sections edge devices, NMS
      hosts should use RFC4191 to make IPsec native and IPsec via GRE subsections.

   o  No need for any assigned dTLS port if automatically learn ACP prefixes.
      This is run across dTLS
      because it is signaled via GRASP.

14.14.  draft-ietf-anima-autonomic-control-plane-08

   Modified mentioning of BRSKI to make it consistent with current
   (07/2017) target for BRSKI: MASA and IDevID are mandatory.  Devices
   with only insecure UDI would need a security reduced variant of
   BRSKI.  Also added mentioning of Netconf Zero-Touch.  Made BRSKI non-
   normative for ACP because wrt. especially necessary when the ACP it is just one option how uses multiple ULA
      prefixes (via e.g., the rsub domain certificate can be provisioned.  Instead, BRSKI option), or if ACP
      connect subinterfaces use manually configured prefixes NOT covered
      by the ACP ULA prefixes.

   o  Explained how rfc6724 is mandatory (only) sufficient when the NMS host has a device implements ANI which is ACP+BRSKI.

   Enhanced text for
      separate ACP across tunnels to decribe two options: one
   across configured tunnels (GRE, IPinIP etc) connect and Data-Plane interface.  But not when there
      is a more efficient one via
   directed DULL.

   Moved decription single interface.

   o  Added a separate subsection to talk about "software" instead of BRSKI
      "NMS hosts" connecting to appendex the ACP via the "ACP connect" method.
      The reason is to emphasize point out that BRSKI the "ACP connect" method is not
      only a (normative) dependency of GRASP, enhanced text workaround (for NMS hosts), but an actual desirable long
      term architectural component to indicate other
   options how Domain Certificates can be provisioned.

   Added terminology section.

   Separated references modularily build software (e.g.,
      ASA or OAM for VNF) into normative and non-normative.

   Enhanced section about ACP via "tunnels".  Defined an option devices.

   o  Added a section to define how to run ACP secure channel without an outer tunnel, discussed PMTU, benefits
   of tunneling, potential of using this with BRSKI, made ACP via GREP a
   SHOULD requirement.

   Moved appendix sections up before IANA section because there where
   concerns about appendices connect across the same
      interface as the Data-Plane.  This turns out to be quite
      challenging because we only want to far rely on existing standards for
      the bottom to be read. network stack in the NMS host/software and only define what
      features the ACP edge device needs.

   o  Added (Informative) / (Normative) to section titles about use of GRASP over ACP connect.

   o  Added text to clarify which
   sections are informative and which are normative

   Moved explanation indicate packet processing/filtering for security:
      filter incorrect packets arriving on ACP connect interfaces,
      diagnose on RPL root packets to incorrect destination address (not
      in ACP connect section, but because of it).

   o  Reaffirm security goal of ACP: Do not permit non-ACP routers into
      ACP routing domain.

   Made this ACP with L2 from precondition to separate
   section before workarounds, made it instructive enough to explain how document be an update to implement ACP on L2 ports for L3/L2 switches RFC4291 and made this part RFC4193.  At the
   core, some of
   normative requirement (L2/L3 switches SHOULD support this).

   Rewrote section "GRASP in the ACP" to define GRASP in ACP addressing sub-schemes do effectively not use
   64-bit IIDs as
   mandatory (and why), required by RFC4191 and define debated in rfc4191bis.  During
   6man in prague, it was suggested that all documents that do not do
   this should be classified as such updates.  Add a rather long section
   that summarizes the relevant parts of ACP as security addressing and transport
   substrate usage and.
   Aka: This section is meant to GRASP in ACP.  And how it works.

   Enhanced "self-protection" properties section: protect legacy
   management protocols.  Security be the primary review section for
   readers interested in these changes (e.g., 6man WG.).

   Added changes from Michael Richardsons review https://github.com/
   anima-wg/autonomic-control-plane/pull/3/commits, textual and:

   o  ACP discovery inside ACP is for protection from outside bad *doh*!.

   o  Better CA trust and those legacy protocols.  Otherwise need end-to-end encryption
   also inside ACP, e.g.: with domain certificate.

   Enhanced initial domain certificate section revocation sentences.

   o  More details about RPL behavior in ACP.

   o  black hole route to include requirements
   for maintenance (renewal/revocation) of certificates. avoid loops in RPL.

   Added
   explanation to BRSKI informative section how requirement to handle very short
   lived certificates (renewal via BRSKI with expired cert).

   Modified the encoding terminate ACP channels upon cert expiry/
   revocation.

   Added fixes from 08-mcr-review-reply.txt (on github):

   o  AN Domain Names are FQDNs.

   o  Fixed bit length of schemes, numerical writing of bits (00b/01b).

   o  Lets use US american english.

14.16.  draft-ietf-anima-autonomic-control-plane-10

   Used the ACP address term routing subdomain more consistently where previously
   only subdomain was used.  Clarified use of routing subdomain in
   creation of ULA "global ID" addressing prefix.

   6.7.1.* Changed native IPsec encapsulation to better fit RFC822 simple
   local-parts (":" as required by RFC5952 are not permitted tunnel mode
   (necessary), explaned why.  Added notion that ESP is used, added
   explanations why tunnel/transport mode in simple
   dot-atoms according native vs. GRE cases.

   6.10.3/6.10.5 Added term "ACP address range/set" to RFC5322.  Removed reference be able to RFC5952 as its
   now not needed anymore.

   Introduced a sub-domain field in better
   explain how the ACP information address in the ACP certificate to allow defining such subdomains with depending on
   future Intent definitions.  It also makes it clear what is actually the "main
   domain" is.  Scheme base
   address (lowest address) of a range/set that is called "routing subdomain" available to have a unique
   name. the
   device.

   6.10.4 Added V8 (now called Vlong) addressing note that manual address sub-scheme according to
   suggestion from mcr in his mail from 30 Nov 2016
   (https://mailarchive.ietf.org/arch/msg/anima/
   nZpEphrTqDCBdzsKMpaIn2gsIzI).  Also modified the addresses must not
   be used within domain certificates (only for explicit configuration).

   6.12.5 Refined explanation of the
   single V bit in the first sub-scheme now renamed to Zone sub-scheme how ACP virtual interfaces work (p2p
   and multipoint).  Did seek for pre-existing RFCs that explain how to distinguish it.

14.15.  draft-ietf-anima-autonomic-control-plane-09
   built a multi-access interface on top of a full mesh of p2p
   connections (6man WG, anima WG mailing lists), but could not find any
   prior work that had a succinct explanation.  So wrote up an
   explanation here.  Added reference to RFC4191 hopefully all necessary and explained sufficient
   details how it should be used on to map ACP
   edge routers unicast packets to allow autoconfiguration of routing by NMS hosts.
   This came after review of stable connectivity draft where ACP connect
   is being referred to.

   V8 addressing Sub-Scheme was modified secure channel, how to allow
   deal with ND packet details.  Added verbage for ACP not only /8 device-
   local address space but also /16.  This was in response to assign the
   possible need to have maybe as much as 2^12 local addresses for
   future encaps in BRSKI like IPinIP.  It also would allow fully
   autonomic
   virtual interface link-local address assignment for ACP connect interfaces from this
   local address space (on an ACP edge device), subject to approval of the implied update to rfc4291/rfc4193 (IID length).  Changed name to
   Vlong addressing sub-scheme. underlying interface.
   Addd note that GRAP link-local messages are treated specially but
   logically the same.  Added text in response to paragraph about NBMA interfaces.

   remaining changes from Brian Carpenters review review.  See Github file
   draft-ietf-anima-autonomic-control-plane/08-carpenter-review-reply.tx
   for more detailst:

   Added multiple new RFC references for terms/technologies used.

   Fixed verbage in several places.

   2. (terminology) Added 802.1AR as reference.

   2.  Fixed up definition of ULA.

   6.1.1 Changed definition of draft-ietf-
   anima-stable-connectivity-04.

   o  The stable connectivity draft was vaguely describing ACP connect
      behavior that is better standardized information in this ACP draft.

   o cert into ABNF format.
   Added new ACP "Manual" addressing sub-scheme with /64 subnets for
      use with warning about maximum size of ACP connect interfaces.  Being covered by the address field due to domain-
   name limitations.

   6.2 Mentioned API requirement between ACP ULA
      prefix, these subnets do and clients leveraging
   adjacency table.

   6.3 Fixed TTL in GRASP example: msec, not require additional routing entries
      for NMS hosts.  They also hop-count!.

   6.8.2 MAYOR: expanded security/transport substrate text:

   Introduced term ACP GRASP virtual interface to explain how GRASP
   link-local multicast messages are fully 64-bit IID length compliant encapsulated and therefore not subject replicated to 4191bis considerations.  And they
      avoid that operators manually assign prefixes from the ACP ULA
      prefixes that might later be assigned autonomiously.

   o  ACP connect auto-configuration: Defined that
   neighbors.  Explain how ACP edge devices, NMS
      hosts should knows when to use RFC4191 TLS vs. TCP (TCP only
   for link-local address (sockets).  Introduced "ladder" picture to automatically learn
   visualize stack.

   6.8.2.1 Expanded discussion/explanation of security model.  TLS for
   GRASP unicsast connections across ACP prefixes.
      This is especially necessary when the ACP uses multiple ULA
      prefixes (via e.g.: the rsub domain certificate option), or if double encryption (plus
   underlying ACP
      connect subinterfaces use manually configured prefixes NOT covered secure channel), but highly necessary to avoid very
   simple man-in-the-middle attacks by the compromised ACP ULA prefixes.

   o  Explained how rfc6724 members on-path.
   Ultimately, this is (only) sufficient when the NMS host has a
      separate ACP connect and data-plane interface. done to ensure that any apps using GRASP can get
   full end-to-end secrecy for information sent across GRASP.  But for
   publically known ASA services, even this will not when there provide 100%
   security (this is a single interface.

   o  Added a separate subsection to talk about "software" instead of
      "NMS hosts" connecting to the ACP via the "ACP connect" method.
      The reason discussed).  Also why double encryption is to point out that the "ACP connect" method is not
      only a workaround (for NMS hosts), but an actual desirable long
      term architectural component
   better/easier solution than trying to modularily build software (e.g.:
      ASA or OAM for VNF) into ACP devices.

   o optimize this.

   6.10.1 Added a discussion about pseudo-random addressing, scanning-
   attaacks (not an issue for ACP).

   6.12.2 New performance requirements section added.

   6.10.1 Added notion to define how to run ACP connect across the same
      interface as the data-plane.  This turns out to be quite
      challenging because we only want to rely on first experiment with existing standards for
      the network stack in addressing
   schemes before defining new ones - we should be flexible enough.

   6.3/7.2 clarified the NMS host/software interactions between MLD and only define DULL GRASP and
   specified what
      features the needs to be done (e.g., in 2 switches doing ACP edge device needs.

   o per L2
   port).

   12.  Added section about use explanations and cross-references to various security
   aspects of GRASP over ACP connect.

   o discussed elsewhere in the document.

   13.  Added IANA requirements.

   Added RFC2119 boilerplate.

14.17.  draft-ietf-anima-autonomic-control-plane-11

   Same text as -10 Unfortunately when uploading -10 .xml/.txt to indicate packet processing/filtering for security:
      filter incorrect packets arriving on ACP connect interfaces,
      diagnose on RPL root packets to incorrect destination address (not
      in ACP connect section, but because of it).

   o  Reaffirm security goal
   datatracker, a wrong version of ACP: Do not permit non-ACP routers into
      ACP routing domain.

   Made this ACP document be an update to RFC4291 and RFC4193.  At .txt got uploaded, only the
   core, some of .xml was
   correct.  This impacts the ACP addressing sub-schemes do effectively not use
   64-bit IIDs as required by RFC4191 -10 html version on datatra cker and debated in rfc4191bis.  During
   6man in prague, it was suggested that all documents that do not do
   this should be classified the
   PDF versions as such updates.  Add a rather long section
   that summarizes well.  Because rfcdiff also compares the relevant parts of ACP addressing .txt
   version, this -11 version was crea ted so that one can compare
   changes from -09 and usage and.
   Aka: This section is meant changes to be the primary review section next version (-12).

14.18.  draft-ietf-anima-autonomic-control-plane-12

   Sheng Jiangs extensive review.  Thanks!  See Github file draft-ietf-
   anima-autonomic-control-plane/09-sheng-review-reply.txt for
   readers interested in these changes (e.g.: 6man WG.).

   Added more
   details.  Many of the larger changes from Michael Richardsons review https://github.com/
   anima-wg/autonomic-control-plane/pull/3/commits, textual and:

   o  ACP discovery inside ACP listed below where inspired by
   the review.

   Removed the claim that the document is bad *doh*!.

   o  Better CA trust updating RFC4291,RFC4193 and revocation sentences.

   o  More details about RPL behavior in ACP.

   o  black hole route
   the section detailling it.  Done on suggestion of Michael Richardson
   - just try to avoid loops describe use of addressing in RPL.

   Added requirement a way that would not
   suggest a need claim update to terminate ACP channels upon cert expiry/
   revocation.

   Added fixes from 08-mcr-review-reply.txt (on github):

   o  AN Domain Names are FQDNs.

   o  Fixed bit length of schemes, numerical writing of bits (00b/01b). architecture.

   Terminology cleanup:

   o  Lets use US american english.

14.16.  draft-ietf-anima-autonomic-control-plane-10

   Used the term routing subdomain more consistently where previously
   only subdomain was used.  Clarified use of routing subdomain  Replaced "device" with "node" in
   creation text.  Kept "device" only when
      referring to "physical node".  Added definitions for those words.
      Includes changes of ULA "global ID" derived terms, especially in addressing:
      "Node-ID" and "Node-Number" in the addressing prefix.

   6.7.1.* Changed native IPsec encapsulation details.

   o  Replaced term "autonomic FOOBAR" with "acp FOOBAR" as whereever
      appropriate: "autonomic" would imply that the node would need to tunnel mode
   (necessary), explaned why.  Added notion
      support more than the ACP, but that ESP is used, added
   explanations why tunnel/transport mode not correct in native vs. GRE most of the
      cases.

   6.10.3/6.10.5 Added term "ACP address range/set"  Wanted to be able make sure that implementers know they only need
      to better
   explain how support/implement ACP - unless stated otherwise.  Includes
      "AN->ACP node", "AN->ACP adjacency table" and so on.

   1 Added explanation in the address introduction about relationship between
   ACP, BRSKI, ANI and Autonomic Networks.

   6.1.1 Improved terminology and features of the certificate
   information field.  Now called domain information field instead of
   ACP information field.  The acp-address field in the domain
   information field is now optional, enabling easier introduction of
   various future options.

   6.1.2 Moved ACP certificate domainer membership check from section 6.6 to (ACP
   secure channels setup) here because it is actually not only used for ACP
   secure channel setup.

   6.1.3 Fix text about certificate renewal after discussion with Max
   Pritikin/Michael Richardson/Brian Carpenter:

   o  Version 10 erroneously assumed that the base
   address (lowest address) of certificate itself could
      store a range/set URL for renewal, but that is available only possible for CRL URLs.
      Text now only refers to the
   device.

   6.10.4 Added note "remembered EST server" without implying
      that manual address sub-scheme addresses must not
   be used within this is stored in the certificate.

   o  Objective for RFC7030/EST domain certificates (only certificate renewal was changed
      to "SRV.est" See also IANA section for explicit configuration).

   6.12.5 Refined explanation explanation.

   o  Removed detail of how ACP virtual interfaces distance based service selection.  This can be
      better done in future work (p2p
   and multipoint).  Did seek because it would require a lot more
      detail for pre-existing RFCs that explain how to
   built a multi-access interface on top good DNS-SD compatible approach.

   o  Removed detail about trying to create more security by using ACP
      address from certificate of a full mesh peer.  After rethinking, this does not
      seem to buy additional security.

   6.10 Added reference to 6.12.5 in initial use of p2p
   connections (6man WG, anima "loopback interface"
   in section 6.10 in result of email discussion michaelR/michaelB.

   10.2 Introduced informational section (diagnostics) because of
   operational experience - ACP/ANI undeployable without at least
   diagnostics like this.

   10.3 Introduced informational section (enabling/disabling) ACP.
   Important to discuss this for security reasons (e.g., why to never
   never auto-enable ANI on brownfield devices), for implementers and to
   answer ongoing questions during WG mailing lists), but could not find any
   prior work meetings about how to deal with
   shutdown interface.

   10.8 Added informational section discussing possible future
   variations of the ACP for potential adopters that had cannot directly use
   the complete solution described in this document unmodified.

14.19.  draft-ietf-anima-autonomic-control-plane-13

   Swap author list (with permission).

   6.1.1.  Eliminate blank lines in definition by making it a succinct explanation.  So wrote up an
   explanation here.  Added hopefully all necessary and sufficient
   details picture
   (reformatting only).

   6.10.3.1 New paragraph: Explained how nodes using Zone-ID != 0 need
   to map ACP unicast packets use Zone-ID != 0 in GRASP so that we can avoid routing/forwarding
   of Zone-ID = 0 prefixes.

   Rest of feedback from review of -12, see
   https://raw.githubusercontent.com/anima-wg/autonomic-control-
   plane/master/draft-ietf-anima-autonomic-control-plane/12-feedback-
   reply.txt

   Review from Brian Carpenter:

   various: Autonomous -> autonomic(ally) in all remaining occurences.

   various: changed "manual (configured)" to ACP secure channel, how "explicitly (configured)"
   to
   deal with ND packet details.  Added verbage for ACP not to assign the
   virtual interface link-local address from the underlying interface.
   Addd note that GRAP link-local messages are treated specially but
   logically exclude the same.  Added paragraph about NBMA interfaces.

   remaining changes from Brian Carpenters review.  See Github file
   draft-ietf-anima-autonomic-control-plane/08-carpenter-review-reply.tx
   for more detailst:

   Added multiple new RFC references for terms/technologies used. option of (SDN controller) automatic configuration
   (no humans involved).

   1.  Fixed verbage in several places. reference to section 9.

   2. (terminology)  Added 802.1AR as reference.

   2.  Fixed up definition of ULA.

   6.1.1 Changed definition of ACP information in cert into ABNF format.
   Added warning about maximum size of ACP address field due loopback interface == internal interface.
   After discus on WG mailing lists, including 6man.

   6.1.2 Defined CDP/OCSP and pointed to domain-
   name limitations. RFC5280 for them.

   6.1.3 Removed "EST-TLS", no objective value needed or beneficial,
   added explanation paragraph why.

   6.2 Mentioned API requirement between ACP and clients leveraging Added to adjacency table. table the interface that a neighbor is
   discovered on.

   6.3 Fixed TTL Simplified CDDL syntax: Only one method per AN_ACP objective
   (because of locators).  Example with two objectives in GRASP example: msec, not hop-count!.

   6.8.2 MAYOR: expanded security/transport substrate text:

   Introduced term ACP GRASP virtual interface to explain how GRASP message.

   6.8.1 Added note about link-local GRASP multicast messages are encapsulated and replicated message to
   neighbors.  Explain how ACP knows when avoid
   confusion.

   8.1.4 Added RFC8028 as recommended on hosts to use TLS vs. TCP (TCP only better support VRF-
   select with ACP.

   8.2.1 Rewrote and Simplified CDDL for link-local address (sockets).  Introduced "ladder" picture to
   visualize stack.

   6.8.2.1 Expanded discussion/explanation of security model.  TLS configured remote peer and
   explanations.  Removed pattern option for
   GRASP unicsast connections across ACP is double encryption (plus
   underlying ACP secure channel), but highly necessary remote peer.  Not important
   enough to avoid very
   simple man-in-the-middle attacks be mandated.

   Review thread started by compromised William Atwood:

   2.  Refined definition of VRF (vs.  MPLS/VPN, LISP, VRF-LITE).

   2.  Refined definition of ACP (ACP includes ACP members on-path.
   Ultimately, this is done to ensure that any apps using GRASP can get
   full end-to-end secrecy for information sent across GRASP.  But for
   publically known ASA services, even this will not provide 100%
   security (this is discussed).  Also why double encryption is the
   better/easier solution than trying to optimize this.

   6.10.1 instance).

   2.  Added discussion about pseudo-random addressing, scanning-
   attaacks (not an issue explanation for ACP).

   6.12.2 New performance requirements section added.

   6.10.1 Added notion "zones" to first experiment with existing addressing
   schemes before defining new ones - we should be flexible enough.

   6.3/7.2 clarified the interactions between MLD and DULL GRASP terminology section and
   specified what needs into
   Zone Addressing Sub Scheme section, relating it to RFC4007 zones
   (from Brian Carpenter).

   4.  Fixed text for ACP4 requirement (Clients of the ACP must not be done (e.g.:
   tied to specific protocol.).

   5.  Fixed step 4. with proposed text.

   6.1.1 Included suggested explanation for rsub semantics.

   6.1.3 must->MUST for at least one EST server in 2 switches doing ACP per L2
   port).

   12. network to
   autonomically renew certs.

   6.7.2 normative: AND MUST NOT (permit weaker crypto options.

   6.7.1.1 also included text denying weaker IPsec profile options.

   6.8.2 Fixed description how to build ACP GRASP virtual interfaces.
   Added explanations and cross-references text that ACP continues to various security
   aspects exist in absence of ACP discussed elsewhere neighbors.

   various: Make sure all "zone" words are used consistently.

   6.10.2/various: fixed 40 bit RFC4193 ULA prefix in the document.

   13.  Added IANA requirements.

   Added RFC2119 boilerplate.

14.17.  draft-ietf-anima-autonomic-control-plane-11

   Same text as -10 Unfortunately when uploading -10 .xml/.txt all examples to
   datatracker, a wrong version
   89b714f3db (thanks MichaelR).

   6.10.1 Removed comment about assigned ULA addressing.  Decision not
   to use it now ancient history of .txt got uploaded, only the .xml was
   correct.  This impacts the -10 html version on datatra cker and the
   PDF versions as well.  Because rfcdiff also compares WG decision making process, not
   worth nothing anymore in the .txt
   version, this -11 version was crea ted so that one can compare
   changes RFC.

   Review from -09 and changes to the next version (-12).

14.18.  draft-ietf-anima-autonomic-control-plane-12

   Sheng Jiangs extensive review.  Thanks!  See Github file draft-ietf-
   anima-autonomic-control-plane/09-sheng-review-reply.txt for more
   details.  Many Yongkang Zhang:

   6.10.5 Fixed length of the larger changes listed below where inspired Node-Numbers in ACP Vlong Addressing Sub-
   Scheme.

14.20.  draft-ietf-anima-autonomic-control-plane-14

   Disclaimer: All new text introduced by
   the review.

   Removed the claim that the document is updating RFC4291,RFC4193 this revision provides only
   additional explanations/ details based on received reviews and
   analysis by the section detailling it.  Done on suggestion of Michael Richardson
   - just try authors.  No changes to describe use of addressing beavior already specified in a way that would not
   suggest a need claim update to architecture.

   Terminology cleanup:

   o  Replaced "device" with "node"
   prior revisions.

   Joel Halpern, review part 3:

   Define/explain "ACP registrar" in text.  Kept "device" only when reply to Joel Halpern review part
   3, resolving primarily 2 documentation issues::

   1.  Unclear how much ACP depends on BRSKI.  ACP document was
       referring unqualified to "physical node".  Added definitions for those words.

      Includes changes of derived terms, especially in addressing:
      "Node-ID" registrars and "Node-Number" Registrar-ID in the
       addressing details.

   o  Replaced term "autonomic FOOBAR" with "acp FOOBAR" as whereever
      appropriate: "autonomic" would imply that the node would need section without explaining what a registrar is,
       leading to
      support more than the ACP, but that is not correct assumption it must be a BRSKI Registrar.

   2.  Unclear how the ACP addresses in most of ACP domain certificates are
       assigned because the
      cases.  Wanted BRSKI document does not defines this, but
       refers to make sure this ACP document.

   Wrt. 1: ACP does NOT depend on BRSKI registrars, instead ANY
   appropriate automated or manual mechanism can be used to enroll ACP
   nodes with ACP domain certificates.  This revision calls defines such
   mechanisms the "ACP registrar" and defines requirements.  this is
   non-normative, because it does not define specific mechanisms that implementers know they only
   need to support/implement be support.  In ANI devices, ACP - unless stated otherwise.  Includes
      "AN->ACP node", "AN->ACP adjacency table" Registrars are BRSKI
   Registrars.  In non-ANI ACP networks, the registrar may simply be a
   person using CLI/web-interfaces to provision domain certificates and so on.

   1 Added explanation
   set the ACP address correctly in the introduction about relationship between
   ACP, BRSKI, ANI and Autonomic Networks.

   6.1.1 Improved terminology ACP domain certificate.

   Wrt. 2.: The BRSKI document does rightfully not define how the ACP
   address assignment and features creation of the certificate
   information field.  Now called ACP domain information field
   has to work because this is independent of BRSKI and needs to follow
   the same rules whatever protocol/mechanisms are used to implement an
   ACP Registrar.  Another set of protocols that could be used instead
   of BRSKI is Netconf/Netconf-Call-Home, but such an alternative ACP information field.  The acp-address field
   Registrar solution would need to be speficied in the domain it's own document.

   Additional text/sections had to be added to detail important
   conditions so that automatic certificate maintenance for ACP nodes
   (with BRSKI or other mechanisms) can be done in a way that as good as
   possible maintains ACP address information field is now optional, enabling easier introduction of
   various future options.

   6.1.2 Moved ACP domainer membership check from section 6.6 to (ACP
   secure channels setup) here nodes across the
   nodes lifetime because it that ACP address is not only used for intended as an identifier
   of the ACP
   secure channel setup.

   6.1.3 Fix text about certificate renewal node.

   Summary of sections added:

      6.1.3.5/6.1.3.6 (normative): re-enrollment of ACP nodes after discussion with Max
   Pritikin/Michael Richardson/Brian Carpenter:

   o  Version 10 erroneously assumed that the
      certificate itself could
      store exiry/failure in a URL for renewal, but way that is only allows to maintain as much
      as possible for CRL URLs.
      Text now only refers ACP address information.

      6.10.7 (normative): defines "ACP Registrar" including requirements
      and how it can perform ACP address assignment.

      10.3 (informative): details / examples about registrars to "remembered EST server" without implying help
      implementers and operators understand easier how they operate, and
      provide suggestion of models that this is stored in a likely very ueful (sub-CA and/
      or centralized policy manaement).

      10.4 (informative): Explains the certificate.

   o  Objective need for RFC7030/EST domain certificate renewal was changed the multiple address
      sub-spaces defined in response to "SRV.est" See also IANA section discuss with Joel.

   Other changes:

   Updated references (RFC8366, RFC8368).

   Introduced sub-section headings for explanation.

   o  Removed detail 6.1.3 (certificate maintenance)
   because section became too long with newly added sub-sections.  Also
   some small text fixups/remove of distance based service selection.  This duplicate text.

   Gen-ART review, Elwyn Davies:

   [RFC Editor: how can be
      better done i raise the issue of problematic cross
   references of terms in future work because it would require a lot more
      detail the terminology section - rendering is
   problematic. ].

   4. added explanation for a good DNS-SD compatible approach.

   o  Removed detail about trying to create more security by using ACP
      address from certificate ACP4 (finally).

   6.1.1 Simplified text in bullet list explaining rfc822 encoding.

   6.1.3 refined second paragraph defining remembering of peer.  After rethinking, this does not
      seem previous EST
   server and explaiing how to buy additional security.

   6.10 do this with BRSKI.

   9.1 Added reference to 6.12.5 in initial use paragraph outlining the benefit of "loopback interface" the sub-CA Registrar
   option for supporting partitioned networks.

   Roughly 100 more nits/minor fixes throughout the document.  See:
   https://raw.githubusercontent.com/anima-wg/autonomic-control-
   plane/master/draft-ietf-anima-autonomic-control-plane/13-elwynd-
   reply.txt

   Joel Halpern, review part 2:

   6.1.1: added note about "+ +" format in section 6.10 address field when acp-
   address and rsub are empty.

   6.5.10 - clarified text about V bit in result Vlong addressing scheme.

   6.10.3/6.10.4 - moved the Z bit field up front (directly after base
   scheme) and indicated more explicitly Z is part of email discussion michaelR/michaelB.

   10.2 Introduced informational section (diagnostics) because selecting of
   operational experience - ACP/ANI undeployable without at least
   diagnostics like this.

   10.3 Introduced informational section (enabling/disabling) ACP.
   Important the
   sub-addressing scheme.

   Refined text about reaching CRL Distribution Point, explain why
   address as indicator to discuss this use ACP.

   Note from Brian Carpenter: RFC Editor note for security reasons (e.g.: why to never
   never auto-enable ANI on brownfield devices), section reference into
   GRASP.

   IOT directorate review from Pascal Thubert:

   Various Nits/typos.

   TBD: Punted wish for implementers and to
   answer ongoing questions during WG meetings about how mentioning RFC reference titles to deal with
   shutdown interface.

   10.8 RFC editor
   for now.

   1.  Added informational section 1.1 - applicability, discussing possible future
   variations protocol choices
   re. applicability to constrained devices (or not).  Added notion of the ACP for potential adopters that cannot directly use
   the complete solution described in this document unmodified.

14.19.  draft-ietf-anima-autonomic-control-plane-13

   Swap author list (with permission).

   6.1.1.  Eliminate blank lines in definition by making it a picture
   (reformatting only).

   6.10.3.1 New paragraph: Explained how nodes using Zone-ID != 0 need
   TCP/TLS va CoAP/DTLS to use Zone-ID != 0 section 10.4 in GRASP so that we can avoid routing/forwarding support of Zone-ID = 0 prefixes.

   Rest this.

   2.  Added in-band / out-of-band into terminology.

   5.  Referenced section 8.2 for remote ACP channel configuration.

   6.3 made M_FLOOD periods RECOMMENDED (less guesswork)

   6.7.x Clarified conditional nature of feedback from review MUST for the profile details of -12, see
   https://raw.githubusercontent.com/anima-wg/autonomic-control-
   plane/master/draft-ietf-anima-autonomic-control-plane/12-feedback-
   reply.txt

   Review from Brian Carpenter:

   various: Autonomous -> autonomic(ally)
   IPsec parameters (aka: onlt 6.7.3 defines actual MUST for nodes,
   prior notions only define the requirements for IPsec profiles IF
   IPsec is supported.

   6.8.1 Moved discussion about IP multicast, IGP, RPL for GRASP into a
   new subsection in all remaining occurances.

   various: changed "manual (configured)" to "explicitly (configured)"
   to not exclude the option of (SDN controller) automatic configuration
   (no humans involved).

   1.  Fixed informative part (section 10) to tighten up
   text in normative part.

   6.10.1 added another reference to section 9.

   2.  Added definition stable-connectivity for interop
   with IPv4 management.

   6.10.1 removed mentioning of loopback interface == internal interface.
   After ULA-Random, term was used in email
   discus on WG mailing lists, including 6man.

   6.1.3 Removed "EST-TLS", no objective value needed or beneficial,
   added explanation paragraph why.

   6.2 Added to adjacency table the interface that a neighbor is
   discovered on.

   6.3 Simplified CDDL syntax: Only one method per AN_ACP objective
   (because of locators).  Example ULA with two objectives L=1, but term actually not defined in GRASP message.

   6.8.1 Added rfc4193, so
   mentioning it is just confusing/redundant.  Also added note about link-local GRASP multicast message to avoid
   confusion.

   8.1.4 Added RFC8028 as recommended on hosts the
   random hash being defined in this document, not using SHA1 from
   rfc4193.

   6.11.1.1 added suggested text about mechanisms to better support VRF-
   select with ACP.

   8.2.1 Rewrote and Simplified CDDL further reduce
   opportunities for configured remote peer loop during reconvergence (active signaling options
   from RFC6550).

   6.11.1.3 made mode 2 MUST and
   explanations.  Removed pattern option mode 2 MAY (RPL MOP - mode of
   operations).  Removes ambiguity ambiguity.

   6.12.5 Added recommendation for remote peer.  Not important
   enough to be mandated. RFC4429 (optimistic DAD).

   Nits from Benjamin Kaduk: dTLS -> DTLS:

   Review thread started by William Atwood:

   2.  Refined definition of VRF (vs.  MPLS/VPN, LISP, VRF-LITE).

   2.  Refined definition from Joel Halpern:

   1. swapped order of ACP (ACP includes ACP GRASP instance).

   2.  Added explanation "purposes" for "zones" ACP to terminology match order in section and into
   Zone Addressing Sub Scheme section, relating it to RFC4007 zones
   (from Brian Carpenter).

   4.  Fixed text for ACP4 requirement (Clients 3.

   1.  Added notion about manageability of the ACP must not be
   tied gong beyond RFC7575
   (before discussion of stable connectivity).

   2.  Changed definition of Intent to specific protocol.).

   5.  Fixed step 4. with proposed text. be same as reference model
   (policy lanuage instead of API).

   6.1.1 Included suggested changed BNF specification so that a local-part without acp-
   address (for future extensions) would not be rfcSELF.+rsub but
   simpler rfcSELF+rsub.  Added explanation for why rsub semantics.

   6.1.3 must->MUST for at least one EST server is in ACP network local-part.

   Tried to
   autonomically renew certs. eliminate unnecessary references to VRF to minimize
   assumption how system is designed.

   6.1.3 Explained how to make CDP reachable via ACP.

   6.7.2 normative: AND Made it clearer that constrained devices MUST NOT (permit weaker crypto options.

   6.7.1.1 also included text denying weaker IPsec support DTLS if
   they can not support IPsec.

   6.8.2.1 clarified first paragraph (TCP restransmissions lightweight).

   6.11.1 fixed up RPL profile options.

   6.8.2 Fixed description how text - to build remove "VRF".  Text was also
   buggy. mentioned control plane, but its a forwarding/silicon issue to
   have these header.

   6.12.5 Clarified how link-local ACP GRASP virtual interfaces.
   Added channel address can be derived,
   and how not.

   8.2.1 Fixed up text that ACP continues to exist in absence distinguish between configuration and model
   describing parameters of ACP neighbors.

   various: Make sure all "zone" words are used consistently.

   6.10.2/various: fixed 40 bit RFC4193 ULA prefix in all examples to
   89b714f3db (thanks MichaelR).

   6.10.1 Removed comment about assigned ULA addressing.  Decision not the configuration (spec only provides
   parameter model).

   Various Nits.

14.21.  wish-list

   From -13 review from Pascal Thubert: Picture to use show dual-NOC routing
   limitation.

   [RFC Editor: Question: Is it now ancient history of WG decision making process, not
   worth nothing anymore in possible to change the RFC.

   Review from Yongkang Zhang:

   6.10.5 Fixed length first occurences
   of Node-Numbers in ACP Vlong Addressing Sub-
   Scheme. [RFCxxxx] references to "rfcxxx title" [RFCxxxx]? the XML2RFC
   format does not seem to offer such a format, but i did not want to
   duplicate 50 first references to be duplicate - one reference for
   title mentioning and one for RFC number.]

15.  References

15.1.  Normative References

   [I-D.ietf-anima-grasp]
              Bormann, C., Carpenter, B., and B. Liu, "A Generic
              Autonomic Signaling Protocol (GRASP)", draft-ietf-anima-
              grasp-15 (work in progress), July 2017.

   [I-D.ietf-cbor-cddl]
              Birkholz, H., Vigano, C., and C. Bormann, "Concise data
              definition language (CDDL): a notational convention to
              express CBOR data structures", draft-ietf-cbor-cddl-02
              (work in progress), February 2018.

   [RFC1034]  Mockapetris, P., "Domain names - concepts and facilities",
              STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
              <https://www.rfc-editor.org/info/rfc1034>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC3810]  Vida, R., Ed. and L. Costa, Ed., "Multicast Listener
              Discovery Version 2 (MLDv2) for IPv6", RFC 3810,
              DOI 10.17487/RFC3810, June 2004,
              <https://www.rfc-editor.org/info/rfc3810>.

   [RFC4191]  Draves, R. and D. Thaler, "Default Router Preferences and
              More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191,
              November 2005, <https://www.rfc-editor.org/info/rfc4191>.

   [RFC4193]  Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
              Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005,
              <https://www.rfc-editor.org/info/rfc4193>.

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, DOI 10.17487/RFC4291, February
              2006, <https://www.rfc-editor.org/info/rfc4291>.

   [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
              December 2005, <https://www.rfc-editor.org/info/rfc4301>.

   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
              DOI 10.17487/RFC4861, September 2007,
              <https://www.rfc-editor.org/info/rfc4861>.

   [RFC4862]  Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
              Address Autoconfiguration", RFC 4862,
              DOI 10.17487/RFC4862, September 2007,
              <https://www.rfc-editor.org/info/rfc4862>.

   [RFC5234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234,
              DOI 10.17487/RFC5234, January 2008,
              <https://www.rfc-editor.org/info/rfc5234>.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246,
              DOI 10.17487/RFC5246, August 2008,
              <https://www.rfc-editor.org/info/rfc5246>.

   [RFC5280]  Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
              Housley, R., and W. Polk, "Internet X.509 Public Key
              Infrastructure Certificate and Certificate Revocation List
              (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
              <https://www.rfc-editor.org/info/rfc5280>.

   [RFC5322]  Resnick, P., Ed., "Internet Message Format", RFC 5322,
              DOI 10.17487/RFC5322, October 2008,
              <https://www.rfc-editor.org/info/rfc5322>.

   [RFC6347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer
              Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
              January 2012, <https://www.rfc-editor.org/info/rfc6347>.

   [RFC6550]  Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J.,
              Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur,
              JP., and R. Alexander, "RPL: IPv6 Routing Protocol for
              Low-Power and Lossy Networks", RFC 6550,
              DOI 10.17487/RFC6550, March 2012,
              <https://www.rfc-editor.org/info/rfc6550>.

   [RFC6552]  Thubert, P., Ed., "Objective Function Zero for the Routing
              Protocol for Low-Power and Lossy Networks (RPL)",
              RFC 6552, DOI 10.17487/RFC6552, March 2012,
              <https://www.rfc-editor.org/info/rfc6552>.

   [RFC6553]  Hui, J. and JP. Vasseur, "The Routing Protocol for Low-
              Power and Lossy Networks (RPL) Option for Carrying RPL
              Information in Data-Plane Datagrams", RFC 6553,
              DOI 10.17487/RFC6553, March 2012,
              <https://www.rfc-editor.org/info/rfc6553>.

   [RFC7030]  Pritikin, M., Ed., Yee, P., Ed., and D. Harkins, Ed.,
              "Enrollment over Secure Transport", RFC 7030,
              DOI 10.17487/RFC7030, October 2013,
              <https://www.rfc-editor.org/info/rfc7030>.

   [RFC7296]  Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
              Kivinen, "Internet Key Exchange Protocol Version 2
              (IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
              2014, <https://www.rfc-editor.org/info/rfc7296>.

   [RFC7676]  Pignataro, C., Bonica, R., and S. Krishnan, "IPv6 Support
              for Generic Routing Encapsulation (GRE)", RFC 7676,
              DOI 10.17487/RFC7676, October 2015,
              <https://www.rfc-editor.org/info/rfc7676>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

15.2.  Informative References

   [AR8021]   IEEE SA-Standards Board, "IEEE Standard for Local and
              metropolitan area networks - Secure Device Identity",
              December 2009, <http://standards.ieee.org/findstds/
              standard/802.1AR-2009.html>.

   [I-D.ietf-anima-bootstrapping-keyinfra]
              Pritikin, M., Richardson, M., Behringer, M., Bjarnason,
              S., and K. Watsen, "Bootstrapping Remote Secure Key
              Infrastructures (BRSKI)", draft-ietf-anima-bootstrapping-
              keyinfra-09
              keyinfra-15 (work in progress), October 2017. April 2018.

   [I-D.ietf-anima-prefix-management]
              Jiang, S., Du, Z., Carpenter, B., and Q. Sun, "Autonomic
              IPv6 Edge Prefix Management in Large-scale Networks",
              draft-ietf-anima-prefix-management-06
              draft-ietf-anima-prefix-management-07 (work in progress),
              October
              December 2017.

   [I-D.ietf-anima-reference-model]
              Behringer, M., Carpenter, B., Eckert, T., Ciavaglia, L.,
              Pierre, P., Liu, B., Nobre, J.,
              and J. Strassner, Nobre, "A Reference Model for Autonomic
              Networking", draft-ietf-
              anima-reference-model-05 (work in progress), October 2017.

   [I-D.ietf-anima-stable-connectivity]
              Eckert, T. and M. Behringer, "Using Autonomic Control
              Plane for Stable Connectivity of Network OAM", draft-ietf-
              anima-stable-connectivity-07 draft-ietf-anima-reference-model-06 (work in
              progress), October
              2017. February 2018.

   [I-D.ietf-netconf-zerotouch]
              Watsen, K., Abrahamsson, M., and I. Farrer, "Zero Touch
              Provisioning for NETCONF or RESTCONF based Management",
              draft-ietf-netconf-zerotouch-19 Networking Devices", draft-ietf-netconf-
              zerotouch-21 (work in progress),
              October 2017. March 2018.

   [I-D.ietf-roll-applicability-template]
              Richardson, M., "ROLL Applicability Statement Template",
              draft-ietf-roll-applicability-template-09 (work in
              progress), May 2016.

   [I-D.ietf-roll-useofrplinfo]
              Robles, I., Richardson, M., and P. Thubert, "When to use
              RFC 6553, 6554 and IPv6-in-IPv6", draft-ietf-roll-
              useofrplinfo-19
              useofrplinfo-23 (work in progress), October 2017. May 2018.

   [LLDP]     IEEE SA-Standards Board, "IEEE Standard for Local and
              Metropolitan Area Networks: Station and Media Access
              Control Connectivity Discovery", June 2016,
              <https://standards.ieee.org/findstds/
              standard/802.1AB-2016.html>.

   [MACSEC]   IEEE SA-Standards Board, "IEEE Standard for Local and
              Metropolitan Area Networks: Media Access Control (MAC)
              Security", June 2006,
              <https://standards.ieee.org/findstds/
              standard/802.1AE-2006.html>.

   [RFC1112]  Deering, S., "Host extensions for IP multicasting", STD 5,
              RFC 1112, DOI 10.17487/RFC1112, August 1989,
              <https://www.rfc-editor.org/info/rfc1112>.

   [RFC1918]  Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G.,
              and E. Lear, "Address Allocation for Private Internets",
              BCP 5, RFC 1918, DOI 10.17487/RFC1918, February 1996,
              <https://www.rfc-editor.org/info/rfc1918>.

   [RFC2315]  Kaliski, B., "PKCS #7: Cryptographic Message Syntax
              Version 1.5", RFC 2315, DOI 10.17487/RFC2315, March 1998,
              <https://www.rfc-editor.org/info/rfc2315>.

   [RFC2821]  Klensin, J., Ed., "Simple Mail Transfer Protocol",
              RFC 2821, DOI 10.17487/RFC2821, April 2001,
              <https://www.rfc-editor.org/info/rfc2821>.

   [RFC4007]  Deering, S., Haberman, B., Jinmei, T., Nordmark, E., and
              B. Zill, "IPv6 Scoped Address Architecture", RFC 4007,
              DOI 10.17487/RFC4007, March 2005,
              <https://www.rfc-editor.org/info/rfc4007>.

   [RFC4364]  Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
              Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February
              2006, <https://www.rfc-editor.org/info/rfc4364>.

   [RFC4429]  Moore, N., "Optimistic Duplicate Address Detection (DAD)
              for IPv6", RFC 4429, DOI 10.17487/RFC4429, April 2006,
              <https://www.rfc-editor.org/info/rfc4429>.

   [RFC4541]  Christensen, M., Kimball, K., and F. Solensky,
              "Considerations for Internet Group Management Protocol
              (IGMP) and Multicast Listener Discovery (MLD) Snooping
              Switches", RFC 4541, DOI 10.17487/RFC4541, May 2006,
              <https://www.rfc-editor.org/info/rfc4541>.

   [RFC4604]  Holbrook, H., Cain, B., and B. Haberman, "Using Internet
              Group Management Protocol Version 3 (IGMPv3) and Multicast
              Listener Discovery Protocol Version 2 (MLDv2) for Source-
              Specific Multicast", RFC 4604, DOI 10.17487/RFC4604,
              August 2006, <https://www.rfc-editor.org/info/rfc4604>.

   [RFC4607]  Holbrook, H. and B. Cain, "Source-Specific Multicast for
              IP", RFC 4607, DOI 10.17487/RFC4607, August 2006,
              <https://www.rfc-editor.org/info/rfc4607>.

   [RFC4610]  Farinacci, D. and Y. Cai, "Anycast-RP Using Protocol
              Independent Multicast (PIM)", RFC 4610,
              DOI 10.17487/RFC4610, August 2006,
              <https://www.rfc-editor.org/info/rfc4610>.

   [RFC4941]  Narten, T., Draves, R., and S. Krishnan, "Privacy
              Extensions for Stateless Address Autoconfiguration in
              IPv6", RFC 4941, DOI 10.17487/RFC4941, September 2007,
              <https://www.rfc-editor.org/info/rfc4941>.

   [RFC5234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234,
              DOI 10.17487/RFC5234, January 2008,
              <https://www.rfc-editor.org/info/rfc5234>.

   [RFC5321]  Klensin, J., "Simple Mail Transfer Protocol", RFC 5321,
              DOI 10.17487/RFC5321, October 2008,
              <https://www.rfc-editor.org/info/rfc5321>.

   [RFC5790]  Liu, H., Cao, W., and H. Asaeda, "Lightweight Internet
              Group Management Protocol Version 3 (IGMPv3) and Multicast
              Listener Discovery Version 2 (MLDv2) Protocols", RFC 5790,
              DOI 10.17487/RFC5790, February 2010,
              <https://www.rfc-editor.org/info/rfc5790>.

   [RFC5880]  Katz, D. and D. Ward, "Bidirectional Forwarding Detection
              (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
              <https://www.rfc-editor.org/info/rfc5880>.

   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <https://www.rfc-editor.org/info/rfc6241>.

   [RFC6335]  Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S.
              Cheshire, "Internet Assigned Numbers Authority (IANA)
              Procedures for the Management of the Service Name and
              Transport Protocol Port Number Registry", BCP 165,
              RFC 6335, DOI 10.17487/RFC6335, August 2011,
              <https://www.rfc-editor.org/info/rfc6335>.

   [RFC6553]  Hui, J. and JP. Vasseur, "The Routing Protocol for Low-
              Power and Lossy Networks (RPL) Option for Carrying RPL
              Information in Data-Plane Datagrams", RFC 6553,
              DOI 10.17487/RFC6553, March 2012,
              <https://www.rfc-editor.org/info/rfc6553>.

   [RFC6724]  Thaler, D., Ed., Draves, R., Matsumoto, A., and T. Chown,
              "Default Address Selection for Internet Protocol Version 6
              (IPv6)", RFC 6724, DOI 10.17487/RFC6724, September 2012,
              <https://www.rfc-editor.org/info/rfc6724>.

   [RFC6762]  Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762,
              DOI 10.17487/RFC6762, February 2013,
              <https://www.rfc-editor.org/info/rfc6762>.

   [RFC6763]  Cheshire, S. and M. Krochmal, "DNS-Based Service
              Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013,
              <https://www.rfc-editor.org/info/rfc6763>.

   [RFC6830]  Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The
              Locator/ID Separation Protocol (LISP)", RFC 6830,
              DOI 10.17487/RFC6830, January 2013,
              <https://www.rfc-editor.org/info/rfc6830>.

   [RFC7404]  Behringer, M. and E. Vyncke, "Using Only Link-Local
              Addressing inside an IPv6 Network", RFC 7404,
              DOI 10.17487/RFC7404, November 2014,
              <https://www.rfc-editor.org/info/rfc7404>.

   [RFC7426]  Haleplidis, E., Ed., Pentikousis, K., Ed., Denazis, S.,
              Hadi Salim, J., Meyer, D., and O. Koufopavlou, "Software-
              Defined Networking (SDN): Layers and Architecture
              Terminology", RFC 7426, DOI 10.17487/RFC7426, January
              2015, <https://www.rfc-editor.org/info/rfc7426>.

   [RFC7575]  Behringer, M., Pritikin, M., Bjarnason, S., Clemm, A.,
              Carpenter, B., Jiang, S., and L. Ciavaglia, "Autonomic
              Networking: Definitions and Design Goals", RFC 7575,
              DOI 10.17487/RFC7575, June 2015,
              <https://www.rfc-editor.org/info/rfc7575>.

   [RFC7576]  Jiang, S., Carpenter, B., and M. Behringer, "General Gap
              Analysis for Autonomic Networking", RFC 7576,
              DOI 10.17487/RFC7576, June 2015,
              <https://www.rfc-editor.org/info/rfc7576>.

   [RFC7721]  Cooper, A., Gont, F., and D. Thaler, "Security and Privacy
              Considerations for IPv6 Address Generation Mechanisms",
              RFC 7721, DOI 10.17487/RFC7721, March 2016,
              <https://www.rfc-editor.org/info/rfc7721>.

   [RFC7761]  Fenner, B., Handley, M., Holbrook, H., Kouvelas, I.,
              Parekh, R., Zhang, Z., and L. Zheng, "Protocol Independent
              Multicast - Sparse Mode (PIM-SM): Protocol Specification
              (Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March
              2016, <https://www.rfc-editor.org/info/rfc7761>.

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,
              <https://www.rfc-editor.org/info/rfc7950>.

   [RFC8028]  Baker, F. and B. Carpenter, "First-Hop Router Selection by
              Hosts in a Multi-Prefix Network", RFC 8028,
              DOI 10.17487/RFC8028, November 2016,
              <https://www.rfc-editor.org/info/rfc8028>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [RFC8366]  Watsen, K., Richardson, M., Pritikin, M., and T. Eckert,
              "A Voucher Artifact for Bootstrapping Protocols",
              RFC 8366, DOI 10.17487/RFC8366, May 2018,
              <https://www.rfc-editor.org/info/rfc8366>.

   [RFC8368]  Eckert, T., Ed. and M. Behringer, "Using an Autonomic
              Control Plane for Stable Connectivity of Network
              Operations, Administration, and Maintenance (OAM)",
              RFC 8368, DOI 10.17487/RFC8368, May 2018,
              <https://www.rfc-editor.org/info/rfc8368>.

Authors' Addresses

   Toerless Eckert (editor)
   Huawei USA - Futurewei Technologies Inc.
   2330 Central Expy
   Santa Clara  95050
   USA

   Email: tte+ietf@cs.fau.de
   Michael H. Behringer (editor)

   Email: michael.h.behringer@gmail.com

   Steinthor Bjarnason
   Arbor Networks
   2727 South State Street, Suite 200
   Ann Arbor  MI 48104
   United States

   Email: sbjarnason@arbor.net