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Versions: (draft-behringer-anima-autonomic-control-plane) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19

ANIMA WG                                               M. Behringer, Ed.
Internet-Draft
Intended status: Standards Track                          T. Eckert, Ed.
Expires: January 4, 2018                                          Huawei
                                                            S. Bjarnason
                                                          Arbor Networks
                                                            July 3, 2017


                       An Autonomic Control Plane
              draft-ietf-anima-autonomic-control-plane-07

Abstract

   Autonomic functions need a control plane to communicate, which
   depends on some addressing and routing.  This Autonomic Control Plane
   should ideally be self-managing, and as independent as possible of
   configuration.  This document defines an "Autonomic Control Plane",
   with the primary use as a control plane for autonomic functions.  It
   also serves as a "virtual out of band channel" for OAM communications
   over a network that is not configured, or mis-configured.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on January 4, 2018.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents



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   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Use Cases for an Autonomic Control Plane  . . . . . . . . . .   4
     2.1.  An Infrastructure for Autonomic Functions . . . . . . . .   5
     2.2.  Secure Bootstrap over an Unconfigured Network . . . . . .   5
     2.3.  Data Plane Independent Permanent Reachability . . . . . .   5
   3.  Requirements  . . . . . . . . . . . . . . . . . . . . . . . .   6
   4.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   7
   5.  Self-Creation of an Autonomic Control Plane . . . . . . . . .   8
     5.1.  Preconditions . . . . . . . . . . . . . . . . . . . . . .   8
       5.1.1.  Domain Certificate with ACP information . . . . . . .   8
       5.1.2.  AN Adjacency Table  . . . . . . . . . . . . . . . . .  10
     5.2.  Neighbor discovery  . . . . . . . . . . . . . . . . . . .  11
       5.2.1.  L2 topology considerations  . . . . . . . . . . . . .  11
       5.2.2.  CDP/LLDP/mDNS considerations  . . . . . . . . . . . .  12
       5.2.3.  Discovery with GRASP  . . . . . . . . . . . . . . . .  12
     5.3.  Candidate ACP Neighbor Selection  . . . . . . . . . . . .  15
     5.4.  Channel Selection . . . . . . . . . . . . . . . . . . . .  15
     5.5.  Candidate ACP Neighbor certificate verification . . . . .  17
     5.6.  Security Association protocols  . . . . . . . . . . . . .  17
       5.6.1.  ACP via IKEv2 . . . . . . . . . . . . . . . . . . . .  17
       5.6.2.  ACP via dTLS  . . . . . . . . . . . . . . . . . . . .  18
       5.6.3.  ACP Security Profiles . . . . . . . . . . . . . . . .  19
     5.7.  GRASP instance details  . . . . . . . . . . . . . . . . .  19
     5.8.  Context Separation  . . . . . . . . . . . . . . . . . . .  19
     5.9.  Addressing inside the ACP . . . . . . . . . . . . . . . .  20
       5.9.1.  Fundamental Concepts of Autonomic Addressing  . . . .  20
       5.9.2.  The ACP Addressing Base Scheme  . . . . . . . . . . .  21
       5.9.3.  ACP Addressing Sub-Scheme . . . . . . . . . . . . . .  22
       5.9.4.  Usage of the Zone Field . . . . . . . . . . . . . . .  23
       5.9.5.  Other ACP Addressing Sub-Schemes  . . . . . . . . . .  24
     5.10. Routing in the ACP  . . . . . . . . . . . . . . . . . . .  24
       5.10.1.  RPL Profile for the ACP  . . . . . . . . . . . . . .  25
     5.11. General ACP Considerations  . . . . . . . . . . . . . . .  25
   6.  Workarounds for Non-Autonomic Nodes . . . . . . . . . . . . .  26
     6.1.  Non-Autonomic Controller / NMS system (ACP connect) . . .  26
     6.2.  ACP through Non-Autonomic L3 Clouds . . . . . . . . . . .  28
   7.  Self-Healing Properties . . . . . . . . . . . . . . . . . . .  28
   8.  Self-Protection Properties  . . . . . . . . . . . . . . . . .  29
   9.  The Administrator View  . . . . . . . . . . . . . . . . . . .  30
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  30



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   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  31
   12. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  31
   13. Change log [RFC Editor: Please remove]  . . . . . . . . . . .  31
     13.1.  Initial version  . . . . . . . . . . . . . . . . . . . .  31
     13.2.  draft-behringer-anima-autonomic-control-plane-00 . . . .  31
     13.3.  draft-behringer-anima-autonomic-control-plane-01 . . . .  32
     13.4.  draft-behringer-anima-autonomic-control-plane-02 . . . .  32
     13.5.  draft-behringer-anima-autonomic-control-plane-03 . . . .  32
     13.6.  draft-ietf-anima-autonomic-control-plane-00  . . . . . .  32
     13.7.  draft-ietf-anima-autonomic-control-plane-01  . . . . . .  33
     13.8.  draft-ietf-anima-autonomic-control-plane-02  . . . . . .  33
     13.9.  draft-ietf-anima-autonomic-control-plane-03  . . . . . .  34
     13.10. draft-ietf-anima-autonomic-control-plane-04  . . . . . .  34
     13.11. draft-ietf-anima-autonomic-control-plane-05  . . . . . .  34
     13.12. draft-ietf-anima-autonomic-control-plane-06  . . . . . .  35
     13.13. draft-ietf-anima-autonomic-control-plane-07  . . . . . .  35
   14. References  . . . . . . . . . . . . . . . . . . . . . . . . .  37
   Appendix A.  Background on the choice of routing protocol . . . .  39
   Appendix B.  Extending ACP channel negotiation (via GRASP)  . . .  41
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  43

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 in the
   document [I-D.ietf-anima-reference-model]

   Autonomic functions need a stable and robust infrastructure to
   communicate on.  This infrastructure should be as robust as possible,
   and it should be re-usable by all autonomic functions.  [RFC7575]
   calls it the "Autonomic Control Plane".  This document defines the
   Autonomic Control Plane.

   Today, the management and control plane of networks typically runs in
   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
   band network has been used to recover from such problems, or
   personnel is sent on site to access devices through console ports
   (craft ports).  However, both options are operationally expensive.

   In increasingly automated networks either controllers or distributed
   autonomic service agents in the network require a control plane which




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   is independent of the network they manage, to avoid impacting their
   own operations.

   This document describes options for a self-forming, self-managing and
   self-protecting "Autonomic Control Plane" (ACP) which is inband on
   the network, yet as independent as possible of configuration,
   addressing and routing problems (for details how this achieved, see
   Section 5).  It therefore remains operational even in the presence of
   configuration errors, addressing or routing issues, or where policy
   could inadvertently affect control plane connectivity.  The Autonomic
   Control Plane serves several purposes at the same time:

   o  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] can run securely inside the ACP and depends
      on the ACP as its "security substrate".

   o  An operator can use it to log into remote devices, even if the
      data plane is misconfigured or unconfigured.

   o  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 dependent
      bootstrap configuration is required.  An example of such a secure
      bootstrap process is described in
      [I-D.ietf-anima-bootstrapping-keyinfra]

   This document describes some use cases for the ACP in Section 2, it
   defines the requirements in Section 3, Section 4 gives an overview
   how an Autonomic Control Plane is constructed, and in Section 5 the
   detailed process is explained.  Section 6 explains how non-autonomic
   nodes and networks can be integrated, and Section 5.6 the first
   channel types for the ACP.

   The document "Autonomic Network Stable Connectivity"
   [I-D.ietf-anima-stable-connectivity] describes how the ACP can be
   used to provide stable connectivity for OAM applications.  It also
   explains on how existing management solutions can leverage the ACP in
   parallel with traditional management models, when to use the ACP
   versus the data plane, how to integrate IPv4 based management, etc.

2.  Use Cases for an Autonomic Control Plane








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2.1.  An Infrastructure for Autonomic Functions

   Autonomic Functions need a stable infrastructure to run on, and all
   autonomic functions should use the same infrastructure to minimise
   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.

2.2.  Secure Bootstrap over an Unconfigured Network

   Today, bootstrapping a new device typically requires all devices
   between a controlling node (such as an SDN controller) and the new
   device to be completely and correctly addressed, configured and
   secured.  Therefore, bootstrapping a network happens in layers around
   the controller.  Without console access (for example through an out
   of band network) it is not possible today to make devices securely
   reachable before having configured the entire network between.

   With the ACP, secure bootstrap of new devices can happen without
   requiring any configuration on the network.  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 through the ACP.

2.3.  Data Plane Independent Permanent Reachability

   Today, most critical control plane protocols and network management
   protocols are running in the 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 on the other: Only if
   the data plane is operational, will the other planes work as
   expected.

   Data plane connectivity can be affected by errors and faults, for
   example certain AAA misconfigurations 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 dependencies also affect NOC/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.






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   The ACP provides reachability that is largely independent of the data
   plane, which allows 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 (VooB) channel", by providing
      connectivity to all devices regardless of their configuration or
      global routing table.

   o  For control plane protocols, the ACP allows their operation even
      when the 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
      connectivity.

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

3.  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.  Reason: traceability, debug-ability, separation from
          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 ULA addressing for this purpose.

   ACP4:  The ACP MUST be generic.  Usable by all the functions and
          protocols of the AN infrastructure.  It MUST NOT be tied to a
          particular 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.





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   The default mode of operation of the ACP is 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 over non-autonomic
   nodes, for example to link autonomic nodes over the general Internet.
   This is possible, but then has a dependency on routing over the non-
   autonomic hops.

4.  Overview

   The Autonomic Control Plane is constructed in the following way (for
   details, see Section 5):

   1.  An autonomic node creates a virtual routing and 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 adjacent nodes in the
       same domain.

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

   4.  It then establishes a secure tunnel of the negotiated channel
       type.  These tunnels are 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 virtual interface with
       its ULA IPv6 address.

   6.  Each node runs a lightweight routing protocol, to announce
       reachability of the virtual addresses inside the ACP.

   Note:

   o  Non-autonomic NMS systems or controllers have to be manually
      connected into the ACP.

   o  Connecting over non-autonomic Layer-3 clouds initially requires a
      tunnel between autonomic nodes.

   o  None of the above operations (except manual ones) is reflected in
      the configuration of the device.

   The following figure illustrates the ACP.





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           autonomic node 1                  autonomic node 2
          ...................               ...................
   secure .                 .   secure      .                 .  secure
   tunnel :  +-----------+  :   tunnel      :  +-----------+  :  tunnel
   ..--------| ACP VRF   |---------------------| ACP VRF   |---------..
          : / \         / \   <--routing-->   / \         / \ :
          : \ /         \ /                   \ /         \ / :
   ..--------|  virtual  |---------------------|  virtual  |---------..
          :  | interface |  :               :  | interface |  :
          :  +-----------+  :               :  +-----------+  :
          :                 :               :                 :
          :   data plane    :...............:   data plane    :
          :                 :    link       :                 :
          :.................:               :.................:

                                 Figure 1

   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
   devices, or if the data plane has issues such as addressing or
   routing problems.

5.  Self-Creation of an Autonomic Control Plane

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

5.1.  Preconditions

   An autonomic node can be a router, switch, controller, NMS host, or
   any other IP device.  We assume an autonomic node has a globally
   unique domain certificate (LDevID), as well as an adjacency table.

5.1.1.  Domain Certificate with ACP information

   To establish an ACP securely, an Autnomic Node MUST have a globally
   unique domain certificate (LDevID), with which it can
   cryptographically assert its membership in the domain.  The document
   [I-D.ietf-anima-bootstrapping-keyinfra] (BRSKI) describes how a
   domain certificate can automatically and securely be derived from a
   vendor specific Unique Device Identifier (UDI) or IDevID certificate.

   The domain certificate (LDevID) of an autonomic node MUST contain
   ANIMA specific information, specifically the domain name, the address



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   of the device in the ACP with the Zone-ID set to zero ("ACP
   address").  This information MUST be encoded in the LDevID in the
   subjectAltName / rfc822Name field in the following way:

   anima.acp+<ACP address>{+<extensions>}@<domain>

   Example:

   anima.acp+FDA3:79A6:F6EE:0:200:0:6400:1@example.com

   The ACP address MUST be specified in its canonical form, as specified
   in [RFC5952], to allow for easy textual comparisons.

   The optional <extensions> field is used for future extensions to this
   specification.  It MUST be ignored unless otherwise specified.

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

   o  The LDevID assigned by BRSKI should be reuseable for other
      purposed beside authentication for ACP.

   o  There are a wide range of pre-existing protocols/services where
      authentication with LDevID is desirable.  Enrolling and
      maintaining separate LDevIDs for each of these protocols/services
      is often undesirable overhead.  Therefore it is beneficial if the
      BRSKI enrolled LDevID can also be used for other protocols/
      services beside the ACP.

   o  The elements in the LDevID required for the ACP should therefore
      not cause incompatibilities with any pre-existing ASN.1 code
      potentially in use in those other pre-existing SW systems.

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

   o  Using an IP address format encoding could result in non-benign
      misinterpretation of the ACP information, for example other
      protocol/services unaware of the ACP could try to do something
      with the ACP address that would fail to work correctly (because it
      is in a different VRF than what they expect), or that could cause
      security issues.




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   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, so that it is easier to
      examine/use the encoded "ACP information".

   o  The format of the rfc822Name is choosen so that an operator can
      set up a mailbox called   anima.acp@<domain> that would receive
      emails sent towards the rfc822Name of any AN device inside a
      domain.  This is possible because components behind a plus symbol
      are considered part of a single mailbox.  In other words, it is
      not necessary to set up a separate mailbox for every autonomic
      devices ACP information, 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.

   In the BRSKI bootstrap process in an ANIMA network, the registrar
   (acting as an EST server) MUST include the subjectAltName /
   rfc822Name encoded ACP address and domain name to the enrolling
   device (called pledge) via its response to the pledges EST CSR
   Attribute request that is mandatory in BRSKI.

   The Certificate Authority in an ANIMA network MUST not change this,
   and create the respective subjectAltName / rfc822Name in the
   certificate.

   ANIMA nodes can therefore find ACP address and domain using this
   field in the domain certificate, both for themselves, as well as for
   other nodes.

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

5.1.2.  AN Adjacency Table

   To know to which nodes to establish an ACP channel, every autonomic
   node maintains an adjacency table.  The adjacency table contains
   information about adjacent autonomic nodes, at a minimum: node-ID, IP
   address, domain, certificate.  An autonomic device MUST maintain this
   adjacency table up to date.  This table is used to determine to which
   neighbor an ACP connection is established.




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   Where the next autonomic device is not directly adjacent, the
   information in the adjacency table can be supplemented by
   configuration.  For example, the node-ID and IP address could be
   configured.

   The adjacency table MAY contain information about the validity and
   trust of the adjacent autonomic node's certificate.  However,
   subsequent steps MUST always start with authenticating the peer.

   The adjacency table contains information about adjacent autonomic
   nodes in general, independently of their domain and trust status.
   The next step determines to which of those autonomic nodes an ACP
   connection should be established.

5.2.  Neighbor discovery

5.2.1.  L2 topology considerations


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

                                 Figure 2

   Consider a large L2 LAN with ANrtr1...ANrtrN connected via some
   topology of L2 switches (eg: in a large enterprise campus or IoT
   environment using large L2 LANs).  If the discovery protocol used for
   the ACP is operating at the subnet level, every AN router will see
   all other AN routers on the LAN as neighbors and a full mesh of ACP
   channels will be built.  If some or all of the 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
   challenges.  The number of security associations of the secure
   channel protocols will not scale arbitrarily, especially when they
   leverage platform accelerated encryption/decryption.  Likewise, any
   other ACP operations needs to scale to the number of direct ACP
   neigbors.  An AN router with just 4 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 support the ACP on arbitrary platforms and in arbitrary
   deployments.

   Predictable scaling requirements for ACP neighbors can most easily be
   achieved if in topologies like these, AN capable L2 switches can



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   ensure that discovery messages terminate on them so that neighboring
   AN routers and switches will only find the physcially connected AN L2
   switches as their candidate ACP neighbors.  With such a discovery
   mechanism in place, the ACP and its security associations will only
   need to scale to the number of physcial interfaces instead of a
   potentially much larger number of "LAN-connected" neighbors.  And the
   ACP topology will follow directly the physical topology, something
   which can then also be leveraged in management operations or by ASAs.

   In the example above, consider ANswitch1 and ANswitchM are AN
   capable, and ANswitch2 is not AN capable.  The desired ACP topology
   is therefore that ANrtr1 and ANrtrM only have an ACP connetion to
   ANswitch1, and that ANswitch1, ANrtr2, ANrtrN have a full mesh of ACP
   connection amongst each other.  ANswitch1 also has an ACP connection
   with ANswitchM and ANswitchM has ACP connections to anything else
   behind it.

5.2.2.  CDP/LLDP/mDNS considerations

   LLDP (and Cisco's 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-ANIMA switches.

   mDNS operates at the subnet level, and is also used on L2 switches.
   The authors of this document are not aware of mDNS implementation
   that terminate their messages on L2 ports instead of the subnet
   level.  If mDNS was used as the ACP discovery mechanism on an ACP
   capable L2 switch, then this would be necessary to implement.  It is
   likely that termination of mDNS messages could only be applied to all
   mDNS messages from a port, which would then make it necessary to
   software forward any non-ACP related mDNS messages to maintain prior
   non-ACP mDNS functionality.  With low performance of software
   forwarding in many L2 switches, this could easily make the ACP
   unsupportable on such L2 switches.

5.2.3.  Discovery with GRASP

   Because of the above considerations, the ACP uses DULL (Discovery
   Unsolicited Link-Local) insecure instances of GRASP for discovery of
   ACP neighbors.  See section 3.5.2.2 of [I-D.ietf-anima-grasp] These
   can easily be set up to match the aforementioned requirements without
   affecting other uses of GRASP.  Note that each such DULL instance of
   GRASP is also used for the discovery of a bootstrap proxy when the
   device is not yet enrolled into the autonomic domain.  Because the
   discover of ACP neighbors only happens after the device is enrolled




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   into the autonomic domain, it never needs to discover a bootstrap
   proxy and ACP neighbor at the same time.

   An autonomic node announces itself to potential ACP peers by use of
   the "AN_ACP" objective.  This is a synchronization objective intended
   to be flooded on a single link using the GRASP Flood Synchronization
   (M_FLOOD) message.  In accordance with the design of the Flood
   message, a locator consisting of a specific link-local IP address, IP
   protocol number and port number will be distributed with the flooded
   objective.  An example of the message is informally:

          [M_FLOOD, 12340815, h'fe80000000000000c0011001FEEF0000, 1,
              ["AN_ACP", SYNCH-FLAG, 1, "IKEv2"],
              [O_IPv6_LOCATOR,
                   h'fe80000000000000c0011001FEEF0000, UDP, 15000]
          ]

   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 = ; as in the GRASP specification
           loop-count = 1    ; limit to link-local operation
           objective-value = text ; name of the (list of) secure
                                  ; channel negotiation protocol(s)

   The objective-flags field is set to indicate synchronization.

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

   The session-id is a random number used for loop prevention
   (distinguishing a message from a prior 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 of the originating
   autonomic node on the sending interface.

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





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   The locator is optional and only required when the secure channel
   protocol is not offered at a well-defined port number, or if there is
   no well defined port number.  For example, "IKEv2" has a well defined
   port number 500, but in the above example, the candidate ACP neighbor
   is offering ACP secure channel negotiation via IKEv2 on port 15000
   (for the sake of creating the example).

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

   The secure channel methods defined in this document use the objective
   values of "IKEv2" and "dTLS".  There is no disstinction between IKEv2
   native and GRE-IKEv2 because this is purely negotiated via IKEv2.

   A node that supports more than one secure channel protocol needs to
   flood multiple versions of the "AN_ACP" objective, each accompanied
   by its own locator.  This can be in a single GRASP M_FLOOD packet.

   If multiple secure channel protocols are supported that all are run
   on well-defined ports, then they can be announced via a single AN_ACP
   objective using a list of string names as the objective value without
   a following locator-option.

   Note that a node serving both as an ACP node and BRSKI Join Proxy may
   choose to distribute the "AN_ACP" objective and "AN_join_proxy"
   objective in the same flood message, since GRASP allows multiple
   objectives in one Flood message.  This may be impractical though if
   ACP and BRSKI operations are implemented via separate software
   modules / ASAs though.

   As explained above, in an ACP enabled L2 switch, each of these GRASP
   instances would actually need to be per-L2-port.  The result of the
   discovery is the IPv6 link-local address of the neighbor as well as
   its supported secure channel protocols (and non-standard port they
   are running on).  It is stored in the AN Adjacency Table, see
   Section 5.1.2 which then drives the further building of the ACP to
   that neighbor.

   For example, ANswitch1 would run separate DULL GRASP instances on its
   ports to ANrtr1, ANswitch2 and ANswitchI, even though all those three
   ports may be in the data plane in the same (V)LAN.  This is easily
   achieved by extracting native GRASP multicast messages by their MAC
   multicast destination address.  None of the other type of GRASP
   instances (eg: as used inside the ACP) use GRASP messages that would
   be affected by such extraction, because all other GRASP messages have
   encrypted encapsulations.




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5.3.  Candidate ACP Neighbor Selection

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

   The ACP is by default established exclusively between nodes in the
   same domain.

   Intent can change this default behaviour.  Since Intent is
   transported over the ACP, the first ACP connection a node establishes
   is always following the default behaviour.  The precise format for
   this Intent needs to be defined outside this document.  Example
   Intent policies which need to be supported include:

   o  The ACP should be built between all sub-domains for a given parent
      domain.  For example: For domain "example.com", nodes of
      "example.com", "access.example.com", "core.example.com" and
      "city.core.example.com" should all establish one single ACP.

   o  Two domains should build one single ACP between themselves, for
      example "example1.com" should establish the ACP also with nodes
      from "example2.com".  For this case, the two domains must be able
      to validate their trust, typically by cross-signing their
      certificate infrastructure.

   The result of the candidate ACP neighbor selection process is a list
   of adjacent or configured autonomic neighbors to which an ACP channel
   should be established.  The next step begins that channel
   establishment.

5.4.  Channel Selection

   To avoid attacks, initial discovery of candidate ACP peers can not
   include any non-protected negotiation.  To avoid re-inventing and
   validating security association mechanisms, the next step after
   discoving the 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 autonomic devices, it is unclear
   whether it is feasible to even decide on a single MTI (mandatory to
   implement) security association protocol across all autonomic
   devices:

   From the use-cases it seems clear that not all type of autonomic
   devices can or need to connect directly to each other or are able to
   support or prefer all possible mechanisms.  For example, code space



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   limited IoT devices may only support dTLS (because that code exists
   already on them for end-to-end security use-cases), but low-end in-
   ceiling L2 switches may only want to support MacSec because that is
   also supported in HW, and only a more flexible gateway device may
   need to support both of these mechanisms and potentially more.

   To support extensible secure channel protocol selection without a
   single common MTI protocol, autonomic devices must try all the ACP
   secure channel protocols it supports and that are feasible because
   the candidate ACP neighbor also announced them via its AN_ACP GRASP
   parameters (these are called the "feasible" ACP secure channel
   protocols).

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

   An autonomic device may choose to attempt initiate the different
   feasible ACP secure channel protocol 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.

   Once the first secure channel protocol succeeds, the two peers know
   each others certificates (because that must be used by all secure
   channel protocols for mutual authentication.  The device with the
   lower Device-ID in the ACP address becomes Bob, the one with the
   higher Device-ID in the certificate Alice.

   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 preferred and the security
   association succeeded.  The roles of Bob abd Alice are then assigned.
   At this stage, the protocol may not even have completed negotiationg
   a common security profile.  The protocol could for example have been
   IPsec.  It is not up to Alice to devide how to proceed.  Even if the
   IPsec connecting determined a working profile with Bob, Alice might
   prefer some other secure protocol (eg: dTLS) and try to set that up
   with Bob. If that succeeds, she would close the IPsec connection.  If
   no better protocol attempt succeeds, she would keep the IPsec
   connection.





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   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 device must not
   assume that neighbors with the same L2 or link-local IPv6 addresses
   on different L2 interfaces are the ame devices.  This can only be
   determined after examining the certificate after a successful
   security association attempt.

5.5.  Candidate ACP Neighbor certificate verification

   Independent of the security association protocol choosen, candidate
   ACP neighbors need to be authenticated based on their autonomic
   domain certificate.  This implies that any security association
   protocol MUST support certificate based authentication that can
   support the following verification steps:

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

   o  The peers certificate is signed by the same CA as the devices
      domain certificate.

   o  The peers certificate has a valid ACP information field
      (subjectAltName / rfc822Name) and the domain name in that peers
      ACP information field is the same as in the devices certificate.

   o  The peers certificate is valid according to the CRL or OCSP method
      indicated in the devices certificate.  If the peers certificate
      fails any of these checks, the connection attempt is aborted and
      an error logged (with throttling).

   This document does not mandate specific support for CRL or OCSP
   options.  If CRL or OCSP URLs are specified in the devices
   certificate then the device SHOULD connect to the URL via the ACP if
   it has an IPv6 address that is reachable via the ACP.  Better
   mechanisms to locate CRL or OCSP server(s), for example via GRASP are
   subject to future documents.

5.6.  Security Association protocols

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

5.6.1.  ACP via IKEv2

   An autonomic device announces its ability to support IKEv2 as the ACP
   secure channel protcol in GRASP as "IKEv2".




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5.6.1.1.  Native IPsec

   To run ACP via IPsec transport mode, no further IANA assignments/
   definitions are required.  All autonomic devices supporting IPsec
   MUST support IPsec security setup via IKEv2, transport mode
   encapsulation via the device and peer link-local IPv6 addresses,
   AES256 encryption and SHA256 hash.

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

5.6.1.2.  IPsec with GRE encapsulation

   In network devices it is often easier to provide virtual interfaces
   on top of GRE encapsulation than natively on top of a simple IPsec
   association.  On those devices it may be necessary to run the ACP
   secure channel on top of a GRE connection protected by the IPsec
   association.  The requirements for the IPsec association are the same
   as in the native IPsec case, but instead of directly carrying the ACP
   IPv6 packets, the payload is an ACP IPv6 packet inside GRE/IPv6.  The
   mandatory security profile is the same as for native IPsec: peer
   link-local IPv6 addresses, AES256 encryption, SHA256 hash.

   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 41 (IPv6) (because native IPsec is required to be
   supported, see below).

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

5.6.2.  ACP via dTLS

   We define the use of ACP via 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 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 autonomic devices supporting
   ACP via dTLS must use AES256 encryption.

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



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5.6.3.  ACP Security Profiles

   A baseline autonomic device MUST support IPsec.  A constrained
   autonomic device MUST support dTLS.  Autonomic edge device connecting
   constrained areas with baseline areas MUST therefore support IPsec
   and dTLS.

   The MTU for ACP secure channels must be derived locally from the
   underlying link MTU minus the security encapsulation overhead.  Given
   how ACP channels are built across layer2 connections only, the
   probability for MTU mismatch is low.  For additional reliability,
   applications to be runa cross the ACP should only assume to have
   minimum MTU available (1280).

   Autonomic devices need to specify in documentation the set of secure
   ACP mechanisms they suppport.

5.7.  GRASP instance details

   Received GRASP packets are assigned to an instance of GRASP by the
   context they are received on:

   o  GRASP packets received on an ACP (virtual) interfaces are assigned
      to the ACP instance of GRASP

   o  GRASP/UDP packets received on L2 interfaces/ports where the device
      is willing to run ACP are assigned to a DULL instance of GRASP for
      that interface/port.

5.8.  Context Separation

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

   In classical network device platforms, a dedicated so called "Virtual
   routing and forwarding instance" (VRF) is one logical implementation
   option for the ACP.  If possible by the platform SW 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 device.  As much as possible it should be protected from being
   modified unintentionally by 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 setup do not affect the ACP.




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5.9.  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 internal
   network wide valid addresses and routing.  Each autonomic node must
   create a virtual interface with a network wide unique address inside
   the ACP context mentioned in Section 5.8.  This address may be used
   also in other virtual contexts.

   With the algorithm introduced here, all autonomic devices in the same
   domain have the same /48 prefix.  Conversely, global IDs from
   different domains are unlikely to clash, such that two networks can
   be merged, as long as the policy allows that merge.  See also
   Section 7 for a discussion on merging domains.

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

5.9.1.  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.

   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 loopback interfaces of autonomic nodes carry a
      routable address; all other interfaces exclusively use IPv6 link
      local for autonomic functions.  The usage of IPv6 link local
      addressing is discussed in [RFC7404].

   o  Use-ULA: For loopback interfaces of autonomic nodes, we use Unique
      Local Addresses (ULA), as specified in [RFC4193].  An alternative
      scheme was discussed, using assigned ULA addressing.  The
      consensus was to use ULA-random [[RFC4193] with L=1], because it
      was deemed to be sufficient.

   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.





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

   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 not require IPv4: The ACP may carry OAM
      protocols.  All relevant protocols (SNMP, TFTP, SSH, SCP, Radius,
      Diameter, ...) are available in IPv6.

5.9.2.  The ACP Addressing Base Scheme

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

     8      40          3                     77
   +--+--------------+------+------------------------------------------+
   |FD| hash(domain) | Type |             (sub-scheme)                 |
   +--+--------------+------+------------------------------------------+

                   Figure 3: 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 ULA "global ID" is set here to be a hash of the domain name,
      which results in a pseudo-random 40 bit value.  It is calculated
      as the first 40 bits of the SHA256 hash of the domain name, in the
      example "example.com".

   o  To allow for extensibility, the fact that the ULA "global ID" is
      such a hash MUST NOT be assumed by any autonomic device during
      normal operations but only by registrars during the creation of a
      response to the CSR Attribute request, eg: when the certificate is
      created in which the address is inserted via the ACP information
      attribute.




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   o  Type: This field allows different address sub-schemes in the
      future.  The goal is to start with a single sub-schemes, but to
      allow for extensions later if and when required.  This addresses
      the "upgradability" requirement.  Assignment of types for this
      field should be maintained by IANA.

5.9.3.  ACP Addressing Sub-Scheme

   The sub-scheme defined here is defined by the Type value 0 (zero) in
   the base scheme.

             51                 13                    63             1
   +------------------------+---------+----------------------------+---+
   |    (base scheme)       | Zone-ID |         Device-ID          | V |
   +------------------------+---------+----------------------------+---+

                    Figure 4: ACP Addressing Sub-Scheme

   The fields are defined as follows: [Editor's note: The lengths of the
   fields is for discussion.]

   o  Zone-ID: If set to all zero bits: The Device-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 Section 5.9.4 on how this field is used in
      detail.

   o  Device-ID: A unique value for each device.

   o  V: Virtualization bit: 0: autonomic node base system; 1: a virtual
      context on an autonomic node.

   The Device-ID is derived as follows: In an Autonomic Network, a
   registrar is enrolling new devices.  As part of the enrolment process
   the registrar assigns a number to the device, which is unique for
   this registrar, but not necessarily unique in the domain.  The 64 bit
   Device-ID is then composed as:

   o  48 bit: Registrar ID, a number unique inside the domain that
      identifies the registrar which assigned the name to the device.  A
      MAC address of the registrar can be used for this purpose.

   o  15 bit: Device number, a number which is unique for a given
      registrar, to identify the device.  This can be a sequentially
      assigned number.

   The "Device-ID" itself is unique in a domain (i.e., the Zone-ID is
   not required for uniqueness).  Therefore, a device can be addressed



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   either as part of a flat hierarchy (zone ID = 0), or with an
   aggregation scheme (any other zone ID).  A address with zone-ID = 0
   is an identifier, with another zone-ID as a locator.  See
   Section 5.9.4 for a description of the zone bits.

   This addressing sub-scheme allows the direct addressing of specific
   virtual containers / VMs on an autonomic node.  An increasing number
   of hardware platforms have a distributed architecture, with a base OS
   for the node itself, and the support for hardware blades with
   potentially different OSs.  The VMs on the blades could be considered
   as separate autonomic nodes, in which case it would make sense to be
   able to address them directly.  Autonomic Service Agents (ASAs) could
   be instantiated in either the base OS, or one of the VMs on a blade.
   This addressing scheme allows for the easy separation of the hardware
   context.

   The location of the V bit(s) at the end of the address allows to
   announce a single prefix for each autonomic node, while having
   separate virtual contexts addressable directly.

   [EDNOTE: various suggestions from mcr in his mail from 30 Nov 2016 to
   be considered (https://mailarchive.ietf.org/arch/msg/anima/
   nZpEphrTqDCBdzsKMpaIn2gsIzI).]

5.9.4.  Usage of the Zone Field

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

   Zone = zero is the default addressing scheme in an autonomic domain.
   Every autonomic node MUST respond to its ACP address with zone=0.
   Used on its own this leads to a non-hierarchical address scheme,
   which is suitable for networks up to a certain size.  In this case,
   the addresses primarily act as identifiers for the nodes, and
   aggregation is not possible.

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

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




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   (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: Another way to introduce hierarchy is to use sub-domains in the
   naming scheme.  The node names "node17.subdomainA.example.com" and
   "node4.subdomainB.example.com" would automatically lead to different
   ULA prefixes, which can be used to introduce a routing hierarchy in
   the network, assuming that the subdomains are aligned with routing
   areas.  Because the domain name in the ACP information field of the
   certificate is used to authenticate an ACP peers certificate, care
   must be taken when using such an approach though: To allow for
   devices in separate subdomains to have mutually permitted
   certificates, the domain part of the ACP information can not carry
   the subdomain.  Instead it shuold be carried as an extension to the
   address part.  This part will be ignored and instead only the address
   field using the different subdomain hash based ULA prefix will be
   used.  Example:
     anima.acp+FDA3:79A6:F6EE:0:200:0:6400:1+sub:subdomainA@example.com

5.9.5.  Other ACP Addressing Sub-Schemes

   Other ACP addressing sub-schemes can be defined if and when required.
   IANA would need to assign a new "type" for each new addressing sub-
   scheme.

5.10.  Routing in 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 the previous section
   for reachability.  The use of the autonomic control plane specific
   context eliminates the probable clash with the global routing table
   and also secures the ACP from interference from the configuration
   mismatch or incorrect routing updates.

   The establishment of the routing plane and its parameters are
   automatic and strictly within the confines of the autonomic control
   plane.  Therefore, no manual configuration is required.

   All routing updates are automatically secured in transit as the
   channels of the autonomic control plane are by default secured, and
   this routing runs only inside the ACP.

   The routing protocol inside the ACP is RPL ([RFC6550]) with the
   following profile.  See Appendix A for more details on the choice of
   RPL.



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5.10.1.  RPL Profile for the ACP

   o  RPL Mode of Operations (MOP): mode 3 "Storing Mode of Operations
      with multicast support".  Implementations should support also
      other modes.  Note: Root indicates mode in DIO flow.

   o  Objective Function (OF): Use OF0 [RFC6552].  No use of metric
      containers, Default RPLInstanceID = 0.

      *  stretch_rank: none provided ("not stretched").

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

   o  Trickle: Not used; Data Path Validation: Not used.

   o  Proactive, aggressive DAO state maintenance:

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

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

   o  Administrative Preference ([RFC6552], 3.2.6 - to become root):
      Indicated in DODAGPreference field of DIO message.

      *  Explicit configured "root": 0b100

      *  Registrar (Default): 0b011

      *  AN-connect (non registrar): 0b010

      *  Default: 0b001.

   The RPL root can create additional RPL instances with other OF and
   metrics as desired, eg: via intent.

5.11.  General ACP Considerations

   In order to be independent of configured link addresses, channels
   SHOULD use IPv6 link local addresses between adjacent neighbors
   wherever possible.  This way, the ACP tunnels are independent of
   correct network wide routing.

   Since channels are by default established between adjacent neighbors,
   the resulting overlay network does hop by hop encryption.  Each node




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   decrypts incoming traffic from the ACP, and encrypts outgoing traffic
   to its neighbors in the ACP.  Routing is discussed in Section 5.10.

   If two nodes are connected via several links, the ACP SHOULD be
   established on 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 of links (for example, a single link),
   reduces resource consumption on the devices, because state needs to
   be kept per ACP channel.

6.  Workarounds for Non-Autonomic Nodes

6.1.  Non-Autonomic Controller / NMS system (ACP connect)

   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 through it.  For
   this, an NMS host must have access to the ACP.  The ACP is a self-
   protecting overlay network, which allows by default access only to
   trusted, autonomic systems.  Therefore, a traditional, non-autonomic
   NMS system does not have access to the ACP by default, just like any
   other external device.

   If the NMS host is not autonomic, i.e., it does not support autonomic
   negotiation of the ACP, then it can be brought into the ACP by
   explicit configuration.  To support connections to adjacent non-
   autonomic nodes, an autonomic node with ACP must support "ACP
   connect" (sometimes also connect "autonomic connect"):

   "ACP connect" is a function on an autonomic device that we call an
   "ACP edge device".  With "ACP connect", interfaces on the device can
   be configured to be put into the ACP VRF.  The ACP is then accessible
   to other (NOC) systems on such an interface without those systems
   having to support any ACP discovery or ACP channel setup.  This is
   also called "native" access to the ACP because to those (NOC) systems
   the interface looks like a normal network interface (without any
   encryption/novel-signaling).












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                                   data-plane "native" (no ACP)
                                              .
  +-----------+           +-----------+       .         +-------------+
  |           |           | Autonomic |       v         |             |+
  |           |           | Device    |-----------------|             |+
  | Autonomic |-----------|"ACP edge  |                 | NOC Device  ||
  | Device    |    ^      | device"   O-----------------| "NMS hosts" ||
  |           |    .      |           | .          ^    |             ||
  +-----------+    .      +-----------+  .         .    +-------------+|
                   .                     .         .     +-------------+
            data-plane "native"          .    ACP "native" (unencrypted)
            + ACP auto-negotiated        .
              and encrypted         ACP connect interface
                                        eg: "vrf ACP native" (config)

                           Figure 5: ACP connect

   ACP connect has security consequences: All systems and processes
   connected via ACP connect have access to all autonomic nodes on the
   entire ACP, without further authentication.  Thus, the ACP connect
   interface and (NOC) systems connected to it must be physically
   controlled/secured.

   The ACP connect interface must be configured with some IPv6 address
   prefix.  This prefix could use the ACP address prefix or could be
   different.  It must be distributed into the ACP routing protocol
   unless the ACP device is the root of the ACP routing protocol (eg:
   when all other autonomic devices have a default route in the ACP
   towards it).  The NOC hosts must route the ACP address prefix to the
   ACP edge devices address on the ACP connect interface.

   An ACP connect interface provides exclusively access to only the ACP.
   This is likely insufficient for many NOC hosts.  Instead, they would
   likely require a second interface outside the ACP for connections
   between the NMS host and administrators, or Internet based services,
   or even for direct access to the data plane.  The document "Autonomic
   Network Stable Connectivity" [I-D.ietf-anima-stable-connectivity]
   explains in more detail how the ACP can be integrated in a mixed NOC
   environment.

   Note: If an NMS host is autonomic itself, it negotiates access to the
   ACP with its neighbor, like any other autonomic node and then runs a
   normal (encrypted) ACP connection to the neighbor.








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6.2.  ACP through Non-Autonomic L3 Clouds

   Not all devices in a network may be autonomic.  If non-autonomic
   Layer-2 devices are between autonomic nodes, the communications
   described in this document should work, since it is IP based.
   However, non-autonomic Layer-3 devices do not forward link local
   autonomic messages, and thus break the Autonomic Control Plane.

   One workaround is to manually configure IP tunnels between autonomic
   nodes across a non-autonomic Layer-3 cloud.  The tunnels are
   represented on each autonomic node as virtual interfaces, and all
   autonomic transactions work across such tunnels.

   Such manually configured tunnels are less "indestructible" than an
   automatically created ACP based on link local addressing, since they
   depend on correct data plane operations, such as routing and
   addressing.

   Future work should envisage an option where the edge device of the L3
   cloud is configured to automatically forward ACP discovery messages
   to the right exit point.  This optimisation is not considered in this
   document.

7.  Self-Healing Properties

   The ACP is self-healing:

   o  New neighbors will automatically join the ACP after successful
      validation and will become reachable using their unique ULA
      address across the ACP.

   o  When any changes happen in the topology, the routing protocol used
      in the ACP will automatically adapt to the changes and will
      continue to provide reachability to all devices.

   o  If an existing device gets revoked, it will automatically be
      denied access to the ACP as its domain certificate will be
      validated against a Certificate Revocation List during
      authentication.  Since the revocation check is 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 device 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.  Devices authenticate each other using the domain
   certificates to establish the ACP locally.  Addressing inside the ACP




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   remains unchanged, and the routing protocol inside both parts of the
   ACP will lead to two working (although partitioned) ACPs.

   There are few central dependencies: A certificate revocation list
   (CRL) may not be available during a network partition; a suitable
   policy to not immediately disconnect neighbors when no CRL is
   available can address this issue.  Also, a registrar or Certificate
   Authority might not be available during a partition.  This may delay
   renewal of certificates that are to expire in the future, and it may
   prevent the enrolment of new devices during the partition.

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

   Merging two networks with different trust anchors requires the trust
   anchors to mutually trust each other (for example, by cross-signing).
   As long as the domain names are different, the addressing will not
   overlap (see Section 5.9).

   It is also highly desirable for implementation of the ACP to be able
   to run it 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 whicht the ACP is
   running.  Especially if bringing down the ACP is known to disconnect
   the operator from the device.  For example any such down
   administrative action could perform a dependency check to see if the
   transport connection across which this action is performed is
   affected by the down action (with default RPL routing used, packet
   forwarding will be symmetric, so this is actually possible to check).

8.  Self-Protection Properties

   As explained in Section 5, the ACP is based on secure channels built
   between devices 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
   and in addition, provide replay protection.

   An attacker will therefore not be able to join the ACP 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.




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   The remaining attack vector would be to attack the underlying AN
   protocols themselves, either via directed attacks or by denial-of-
   service attacks.  However, as the ACP is built using link-local IPv6
   address, remote attacks are impossible.  The ULA addresses are only
   reachable inside the ACP context, therefore unreachable from the data
   plane.  Also, the ACP protocols should be implemented to be attack
   resistant and not consume unnecessary resources even while under
   attack.

9.  The Administrator View

   An ACP is self-forming, self-managing and self-protecting, therefore
   has minimal dependencies on the administrator of the 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 enable or disable the entire approach, but
   detailed configuration is not possible.  This means that the ACP must
   not be reflected in the running configuration of devices, 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 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 to deal with ACP aspect unless they explicitly desire to
   do so.

   Since an ACP is self-protecting, a device not supporting the 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 6.1 for more details on how to
   connect an NMS host into the ACP.

10.  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




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      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, (s)he can
   spoof all addresses inside the ACP and fake messages from any other
   device.

   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.

11.  IANA Considerations

12.  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, Ravi
   Kumar Vadapalli.

   Special thanks to Pascal Thubert to provide the details for the
   recommendations of the RPL profile to use in the ACP

   Further input and suggestions were received from: Rene Struik, Brian
   Carpenter, Benoit Claise.

13.  Change log [RFC Editor: Please remove]

13.1.  Initial version

   First version of this document: draft-behringer-autonomic-control-
   plane

13.2.  draft-behringer-anima-autonomic-control-plane-00

   Initial version of the anima document; only minor edits.







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13.3.  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.

13.4.  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

13.5.  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.  This goes a bit throughout the document, starting
      with a changed abstract and intro.

13.6.  draft-ietf-anima-autonomic-control-plane-00

   No changes; re-submitted as WG document.






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13.7.  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 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.

13.8.  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.








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13.9.  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 5.1.

   o  Editorial changes, updated draft references, etc.

13.10.  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).

13.11.  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.





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   o  Section 5.9.1 (addressing): State that addresses in the ACP are
      permanent, and do not support temporary addresses as defined in
      RFC4941.

   o  Modified Section 5.2.3 to point to the GRASP objective defined in
      [I-D.carpenter-anima-ani-objectives]. (and added that reference)

   o  Section 5.9.2: 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 6.1 the ACP Connect port, and defined that
      term "ACP Connect".

   o  Section 6.2: Added some thoughts (from mcr) on how traversing a L3
      cloud could be automated.

   o  Added a CRL check in Section 5.6.

   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).

13.12.  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.

13.13.  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.




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   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" 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 of the certificate
      instead of the OU in the certificate.  Also renewed the text
      pointing out that the ACP information 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 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,
      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  Took the text for the GRASP discovery of ACP neighbors from Brians
      grasp-ani-objectives draft.  Alas, that draft was behind the
      latest GRASP draft, so i had to overhaul.  The mayor change is to
      describe in the ACP draft the whole format of the M_FLOOD message
      (and not only the actual objective).  This should make it a lot
      easier to read (without having to go back and forth to the GRASP
      RFC/draft).  It was also necessary because the locator in the
      M_FLOOD messages has an important role and its not coded inside
      the objective.  The specification of how to format the M_FLOOD
      message shuold now be complete, the text may be some duplicate
      with the DULL specificateion in GRASP, but no contradiction.

   o  One of the main outcomes of reworking the GRASP section was the
      notion that GRASP announces both the candidate peers IPv6 link



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      local address but also the support ACP security protocol including
      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 using this information are
      negligible: If an attacker on 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  Removed the section on discovery and BRSKI.  This can be revived
      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.

   o  Tried to resolve the EDNOTE about CRL vs. OCSP by pointing out we
      do not specify which one is to be used but that the ACP should be
      used to reach the URL included in the certificate to get to the
      CRL storage or OCSP server.

   o  Changed ACP via IPsec to 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 is run across dTLS
      because it is signalled via GRASP.

14.  References

   [I-D.carpenter-anima-ani-objectives]
              Carpenter, B. and B. Liu, "Technical Objective Formats for
              the Autonomic Network Infrastructure", draft-carpenter-
              anima-ani-objectives-02 (work in progress), June 2017.

   [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-06 (work in progress), May 2017.

   [I-D.ietf-anima-grasp]
              Bormann, C., Carpenter, B., and B. Liu, "A Generic
              Autonomic Signaling Protocol (GRASP)", draft-ietf-anima-
              grasp-14 (work in progress), July 2017.

   [I-D.ietf-anima-reference-model]
              Behringer, M., Carpenter, B., Eckert, T., Ciavaglia, L.,
              Pierre, P., Liu, B., Nobre, J., and J. Strassner, "A
              Reference Model for Autonomic Networking", draft-ietf-
              anima-reference-model-04 (work in progress), July 2017.



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   [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-02 (work in progress), February
              2017.

   [I-D.richardson-anima-6join-discovery]
              Richardson, M., "GRASP discovery of Registrar by Join
              Assistant", draft-richardson-anima-6join-discovery-00
              (work in progress), October 2016.

   [RFC4122]  Leach, P., Mealling, M., and R. Salz, "A Universally
              Unique IDentifier (UUID) URN Namespace", RFC 4122,
              DOI 10.17487/RFC4122, July 2005,
              <http://www.rfc-editor.org/info/rfc4122>.

   [RFC4193]  Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
              Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005,
              <http://www.rfc-editor.org/info/rfc4193>.

   [RFC4941]  Narten, T., Draves, R., and S. Krishnan, "Privacy
              Extensions for Stateless Address Autoconfiguration in
              IPv6", RFC 4941, DOI 10.17487/RFC4941, September 2007,
              <http://www.rfc-editor.org/info/rfc4941>.

   [RFC5082]  Gill, V., Heasley, J., Meyer, D., Savola, P., Ed., and C.
              Pignataro, "The Generalized TTL Security Mechanism
              (GTSM)", RFC 5082, DOI 10.17487/RFC5082, October 2007,
              <http://www.rfc-editor.org/info/rfc5082>.

   [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,
              <http://www.rfc-editor.org/info/rfc5280>.

   [RFC5952]  Kawamura, S. and M. Kawashima, "A Recommendation for IPv6
              Address Text Representation", RFC 5952,
              DOI 10.17487/RFC5952, August 2010,
              <http://www.rfc-editor.org/info/rfc5952>.

   [RFC6347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer
              Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
              January 2012, <http://www.rfc-editor.org/info/rfc6347>.







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   [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,
              <http://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,
              <http://www.rfc-editor.org/info/rfc6552>.

   [RFC6762]  Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762,
              DOI 10.17487/RFC6762, February 2013,
              <http://www.rfc-editor.org/info/rfc6762>.

   [RFC6763]  Cheshire, S. and M. Krochmal, "DNS-Based Service
              Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013,
              <http://www.rfc-editor.org/info/rfc6763>.

   [RFC7404]  Behringer, M. and E. Vyncke, "Using Only Link-Local
              Addressing inside an IPv6 Network", RFC 7404,
              DOI 10.17487/RFC7404, November 2014,
              <http://www.rfc-editor.org/info/rfc7404>.

   [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,
              <http://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,
              <http://www.rfc-editor.org/info/rfc7576>.

   [RFC7676]  Pignataro, C., Bonica, R., and S. Krishnan, "IPv6 Support
              for Generic Routing Encapsulation (GRE)", RFC 7676,
              DOI 10.17487/RFC7676, October 2015,
              <http://www.rfc-editor.org/info/rfc7676>.

Appendix A.  Background on the choice of routing protocol

   In a pre-standard implementation, the "IPv6 Routing Protocol for Low-
   Power and Lossy Networks (RPL, [RFC6550] was chosen.  This
   Appendix explains the reasoning behind that decision.

   Requirements for routing in the ACP are:



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   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 synchronisation.

   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 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 behaviour.

   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.



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   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 optimisation: 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 optimisation
      schemes become necessary in the future, but RPL can be expanded
      (see point "Extensibility" above).

Appendix B.  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 and some form of 802.1AE (MacSEC) are to be added as
   negotiation options - and the performance objective should work



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   across all IPsec, dDTLS and 802.1AE 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 multitide 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 devices 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 is
      highly reduced.

   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.




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Authors' Addresses

   Michael H. Behringer (editor)

   Email: mchael.h.behringer@gmail.com


   Toerless Eckert (editor)
   Futurewei Technologies Inc.
   2330 Central Expy
   Santa Clara  95050
   USA

   Email: tte+ietf@cs.fau.de


   Steinthor Bjarnason
   Arbor Networks
   2727 South State Street, Suite 200
   Ann Arbor  MI 48104
   United States

   Email: sbjarnason@arbor.net




























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