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Versions: (draft-behringer-autonomic-control-plane) 00 01 02 03 draft-ietf-anima-autonomic-control-plane

ANIMA                                                       M. Behringer
Internet-Draft                                              S. Bjarnason
Intended status: Standards Track                              Balaji. BL
Expires: August 24, 2015                                       T. Eckert
                                                                   Cisco
                                                       February 20, 2015


                       An Autonomic Control Plane
            draft-behringer-anima-autonomic-control-plane-01

Abstract

   In certain scenarios, for example when bootstrapping a network, it is
   desirable to automatically bring up a secure, routed control plane,
   which is independent of device configurations and global routing
   table.  This document describes an approach for a logically separated
   "Autonomic Control Plane", which can be used as a "virtual out of
   band channel" - a self-managing overlay network, which is independent
   of configuration, addressing and routing on the data plane.

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 August 24, 2015.

Copyright Notice

   Copyright (c) 2015 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
   carefully, as they describe your rights and restrictions with respect



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   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Problem Statement . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Self-Creation of an Autonomic Control Plane . . . . . . . . .   4
     3.1.  Preconditions . . . . . . . . . . . . . . . . . . . . . .   4
     3.2.  Adjacency Discovery . . . . . . . . . . . . . . . . . . .   4
     3.3.  Authenticating Neighbors  . . . . . . . . . . . . . . . .   5
     3.4.  Capability Negotiation  . . . . . . . . . . . . . . . . .   6
     3.5.  Channel Establishment . . . . . . . . . . . . . . . . . .   6
     3.6.  Context Separation  . . . . . . . . . . . . . . . . . . .   7
     3.7.  Addressing in the ACP . . . . . . . . . . . . . . . . . .   7
     3.8.  Routing in the ACP  . . . . . . . . . . . . . . . . . . .   8
     3.9.  Connecting a Controller / NMS system  . . . . . . . . . .   8
   4.  Self-Healing Properties . . . . . . . . . . . . . . . . . . .   9
   5.  Self-Protection Properties  . . . . . . . . . . . . . . . . .  10
   6.  Use Cases for the ACP . . . . . . . . . . . . . . . . . . . .  10
   7.  The Administrator View  . . . . . . . . . . . . . . . . . . .  11
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  12
   11. Change log [RFC Editor: Please remove]  . . . . . . . . . . .  12
     11.1.  Initial version  . . . . . . . . . . . . . . . . . . . .  12
     11.2.  version 00 . . . . . . . . . . . . . . . . . . . . . . .  12
     11.3.  version 01 . . . . . . . . . . . . . . . . . . . . . . .  12
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14

1.  Introduction

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




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   This document describes a self-forming, self-managing and self-
   protecting "Autonomic Control Plane" (ACP) which is inband on the
   network, yet independent of configuration, addressing and routing
   problems (for details how this achieved, see Section 3).  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:

   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.pritikin-anima-bootstrapping-keyinfra]

   o  Devices can use the ACP for direct decentralised communications,
      such as negotiations or discovery.  The ACP therefore supports
      directly Autonomic Networking functions, as described in
      [I-D.behringer-anima-reference-model].

   This document describes how the Autonomic Control Plane is
   constructed, and some use cases for it.  A more detailed use case
   description on how the Autonomic Control Plane can be used to provide
   stable connectivity for OAM applications is discussed in the document
   "Autonomic Network Stable Connectivity"
   [I-D.eckert-anima-stable-connectivity].

   The Autonomic Control plane relies exclusively on IPv6 for its
   operation, and all operations in the ACP are exclusively IPv6.  Since
   the ACP is a new approach, there should be no need to support dual
   stack IPv4/v6.  The network operator can configure the network data
   plane for any protocol, including IPv4 or IPv6.

2.  Problem Statement

   An "Autonomic Control Plane" (ACP) provides a solution to some of
   today's operational challenges.  These fall into three broad
   categories:

   o  Bootstrapping a network while devices are not yet configured.
      Bootstrapping a new device typically requires all devices between
      the 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



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      access it is not possible today to make devices securely reachable
      before having configured the entire network between.

   o  Maintaining reachability of network devices even in the case of
      certain forms of misconfiguration and routing issues.  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.

   o  Data plane dependencies for 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;
      an ACP would simplify them.

3.  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.

3.1.  Preconditions

   Each autonomic device has a globally unique domain certificate, with
   which it can cryptographically assert its membership of the domain.
   The document [I-D.pritikin-anima-bootstrapping-keyinfra] describes
   how a domain certificate can be automatically and securely derived
   from a vendor specific Unique Device Identifier (UDI) or IDevID
   certificate.  (Note the UDI used in this document is NOT the UUID
   specified in [RFC4122].)

3.2.  Adjacency Discovery

   Adjacency discovery exchanges identity information about neighbors,
   either the UDI or, if present, the domain certificate (see
   Section 3.1.  This document assumes the existence of a domain
   certificate.

   Adjacency discovery provides a table of information of adjacent
   neighbors.  Each neighbor is identified by a globally unique device
   identifier (UDI).





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   The adjacency table contains the following information about the
   adjacent neighbors.

   o  Globally valid Unique device identifier (UDI).

   o  Link Local IPv6 address with its scope.

   o  Trust information: The certificate chain, if available.

   o  Validity of the trust (once validated, see next section).

   Adjacency discovery can populate this table by several means.  One
   such mechanism is to discover using link local multicast probes,
   which has no dependency on configured addressing and is preferable in
   an autonomic network.

   The "Generic Discovery and Negotiation Protocol" GDNP described in
   [I-D.carpenter-anima-gdn-protocol] is a possible candidate protocol
   to meet the requirements for Adjacency Discovery described here.

3.3.  Authenticating Neighbors

   Each neighbor in the adjacency table is authenticated.  The result of
   the authentication of the neighbor information is stored in the
   adjacency table.  We distinguish the following cases:

   o  Inside the domain: If the domain certificate presented is
      validated (including proof of possession of the corresponding
      private key) to be in the same domain as that of the autonomic
      entity then the neighbor is deemed to be inside the autonomic
      domain.  Only entities inside the autonomic domain will by default
      be able to establish the autonomic control plane.  Alternatively,
      policy can define whether to simply trust devices with the same
      trust anchor.  An ACP channel will be established.

   o  Outside the domain: If there is no domain certificate presented by
      the neighbor, or if the domain certificate presented is invalid or
      expired, then the neighbor is deemed to be outside the autonomic
      domain.  No ACP channel will be established.

   Certificate management questions such as enrolment, revocation,
   renewal, etc, are not discussed in this draft.  Please refer to
   [I-D.pritikin-anima-bootstrapping-keyinfra] for more details.

   Authentication could be a function of a generic Adjacency Discovery
   protocol, for example the "Generic Discovery and Negotiation
   Protocol" GDNP described in [I-D.carpenter-anima-gdn-protocol].




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3.4.  Capability Negotiation

   Autonomic devices have different capabilities based on the type of
   device and where it is deployed.  To establish a trusted secure
   communication channel, devices must be able to negotiate with each
   neighbor a set of parameters for establishing the communication
   channel, most notably channel type and security type.  the
   communication channel, most notably channel type and security type.
   The channel type could be any tunnel mechanism that is feasible
   between two adjacent neighbors, for example a GRE tunnel.  The
   security type could be any of the channel protection mechanism that
   is available between two adjacent neighbors on a given channel type,
   for example DTLS or IPsec.  The establishment of the autonomic
   control plane can happen after the channel type and security type is
   negotiated.

   The "Generic Discovery and Negotiation Protocol GDNP described in
   [I-D.carpenter-anima-gdn-protocol] is a possible candidate protocol
   to meet the requirements for capability negotiation described here.

3.5.  Channel Establishment

   After authentication and capability negotiation autonomic nodes
   establish a secure channel towards their direct AN neighbors with the
   above negotiated parameters.  In order to be independent of
   configured link addresses, these channels can be implemented in
   several ways:

   o  As a secure IP tunnel (e.g., IPsec, DTLS, etc.), using IPv6 link
      local addresses between two adjacent neighbors.  This way, the ACP
      tunnels are independent of correct network wide routing.  They
      also do not require larger than link local scope addresses, which
      would normally need to be configured or maintained.  Each AN node
      MUST support this function.

   o  L2 separation, for example via a separate 802.1q tag for ACP
      traffic.  This even further reduces dependency against the data
      plane (not even IPv6 link-local there required), but may be harder
      to implement.

   Since channels are established between adjacent neighbors, the
   resulting overlay network does hop by hop encryption.  Each node
   decrypts incoming traffic from the ACP, and encrypts outgoing traffic
   to its neighbors in the ACP.  Routing is discussed in Section 3.8.

   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



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   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.

3.6.  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.
   The context for the ACP needs to be established automatically during
   bootstrap of a device and - as necessitated by the implementation
   option be protected from being modified unintential from data plane
   configuration.

   In addition this provides for 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.

3.7.  Addressing in the ACP

   The channels explained above only establish communication between two
   adjacent neighbors.  In order for the communication to happen across
   multiple hops, the autonomic control plane requires internal network
   wide valid addresses and routing.  Each autonomic node must create a
   loop back interface with a network wide unique address inside the ACP
   context mentioned in Section 3.6.

   We suggest to create network wide Unique Local Addresses (ULA) in
   accordance with [RFC4193] with the following algorithm:

   o  Prefix FC01::/8

   o  Global ID: a hash of the domain ID; this way all devices in the
      same domain have the same /48 prefix.  Conversely, global ID 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 4 for a discussion on merging domains.

   o  Subnet ID and interface ID: These can be either derived
      deterministically from the name of the device, or assigned at
      registration time of the device.



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3.8.  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.

   The routing protocol inside the ACP should be light weight and highly
   scalable to ensure that the ACP does not become a limiting factor in
   network scalability.  We suggest the use of RPL as one such protocol
   which is light weight and scales well for the control plane traffic.

3.9.  Connecting a Controller / NMS system

   The Autonomic Control Plane can be used by management systems, such
   as controllers or network management system (NMS) hosts (henceforth
   called simply "NMS hosts"), to connect to devices through it.  For
   this, an NMS host must have access to the ACP.  By default, the ACP
   is a self-protecting overlay network, which only allows access to
   trusted systems.  Therefore, a traditional NMS system does not have
   access to the ACP by default, just like any other external device.

   The preferred way for an NMS host to connect to the ACP of a network
   is to enrol that NMS host as a domain device, such that it shares a
   domain certificate with the same trust anchor as the network devices.
   Then, the NMS host can automatically discover an adjacent network
   element, and join the ACP automatically, just like a network device
   would connect to a neighboring device.  Alternatively, if there is no
   directly connected autonomic network element, a secure connection to
   a single remote network element can be established by configuration,
   authenticated using the domain certificates.  There, the NMS host
   "enters" the ACP, from which point it can use the ACP to reach
   further nodes.

   If the NMS host does not support autonomic negotiation of the ACP,
   then it can be brought into the ACP by configuration.  On an adjacent
   autonomic node with ACP, the interface with the NMS host can be
   configured to be part of the ACP.  In this case, the NMS host is with



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   this interface entirely and exclusively inside the ACP.  It would
   likely require a second interface for connections between the NMS
   host and administrators, or Internet based services.  This mode of
   connecting an NMS host has security consequences: All systems and
   processes connected to this implicitly trusted interface have access
   to all autonomic nodes on the entire ACP, without further
   authentication.  Thus, this connection must be physically controlled.

   In both options, the NMS host must be routed in the ACP.  This
   involves two parts: 1) the NMS host must point default to the AN
   device for all IPv6, or for the ULA prefix used inside the ACP, and
   2) the prefix used between AN node and NMS host must be announced
   into the ACP, and distributed there.

4.  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.

   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
   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 merge will just establish the previous
   status, certificates can be renewed, the CRL is available, and new



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   devices can be enrolled everywhere.  Since all devices use the same
   trust anchor, a 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 3.7).

5.  Self-Protection Properties

   As explained in Section 3, the ACP is based on channels being built
   between devices which have been previously authenticated based on
   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.

   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.

6.  Use Cases for the ACP

   The ACP automatically enables a number of use cases which provide
   immediate benefits:

   o  Secure bootstrap of new devices without requiring any
      configuration.  As explained in Section 3, a new device will
      automatically be bootstrapped in a secure fashion and be deployed
      with a domain certificate.  This will happen without any
      configuration, allowing a new device to be shipped directly to the
      end-user location without the need for any pre-provisioning.

   o  Virtual-out-of-band (VooB) control plane which provides
      connectivity to all devices regardless of their configuration or
      global routing table.  This makes it possible to manage devices
      without having to configure data plane services or to deploy a



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      separate management network.  It also simplifies management
      applications, because changes done by the applications cannot
      affect reachability of the devices.

7.  The Administrator View

   An ACP is self-forming, self-managing and self-protecting, therefore
   has minimal dependencies on the administrator of the network.
   Specifically, it cannot be configured, there is therefore 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 3.9 for more details on how to
   connect an NMS host into the ACP.

8.  Security Considerations

   An ACP is self-protecting and there is no need to apply configuration
   to make it secure.  Its security therefore does not depend on
   configuration.

   However, the security of the ACP depends on a number of other
   factors:

   o  The usage of domain certificates depends on a valid supporting PKI
      infrastructure.  If the chain of trust of this PKI infrastructure
      is compromised, the security of the ACP is also compromised.  This
      is typically under the control of the network administrator.

   o  Security can be compromised by implementation errors (bugs), as in
      all products.




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   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.

9.  IANA Considerations

   This document requests no action by IANA.

10.  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, Alex
   Clemm, Toerless Eckert, Yves Hertoghs, Bruno Klauser, Max Pritikin,
   Ravi Kumar Vadapalli.

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

11.  Change log [RFC Editor: Please remove]

11.1.  Initial version

   First version of this document:
   [I-D.behringer-autonomic-control-plane]

11.2.  version 00

   Initial version of the anima document; only minor edits.

11.3.  version 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.






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   o  Added a discussion on network split and merge.  Although, this
      should probably go into the certificate management story longer
      term.

12.  References

   [I-D.behringer-anima-reference-model]
              Behringer, M., Carpenter, B., and T. Eckert, "A Reference
              Model for Autonomic Networking", draft-behringer-anima-
              reference-model-00 (work in progress), October 2014.

   [I-D.behringer-autonomic-control-plane]
              Behringer, M., Bjarnason, S., BL, B., and T. Eckert, "An
              Autonomic Control Plane", draft-behringer-autonomic-
              control-plane-00 (work in progress), June 2014.

   [I-D.carpenter-anima-gdn-protocol]
              Carpenter, B. and B. Liu, "A Generic Discovery and
              Negotiation Protocol for Autonomic Networking", draft-
              carpenter-anima-gdn-protocol-01 (work in progress),
              January 2015.

   [I-D.eckert-anima-stable-connectivity]
              Eckert, T. and M. Behringer, "Autonomic Network Stable
              Connectivity", draft-eckert-anima-stable-connectivity-00
              (work in progress), October 2014.

   [I-D.irtf-nmrg-an-gap-analysis]
              Jiang, S., Carpenter, B., and M. Behringer, "Gap Analysis
              for Autonomic Networking", draft-irtf-nmrg-an-gap-
              analysis-03 (work in progress), December 2014.

   [I-D.irtf-nmrg-autonomic-network-definitions]
              Behringer, M., Pritikin, M., Bjarnason, S., Clemm, A.,
              Carpenter, B., Jiang, S., and L. Ciavaglia, "Autonomic
              Networking - Definitions and Design Goals", draft-irtf-
              nmrg-autonomic-network-definitions-05 (work in progress),
              December 2014.

   [I-D.pritikin-anima-bootstrapping-keyinfra]
              Pritikin, M., Behringer, M., and S. Bjarnason,
              "Bootstrapping Key Infrastructures", draft-pritikin-anima-
              bootstrapping-keyinfra-01 (work in progress), February
              2015.

   [RFC4122]  Leach, P., Mealling, M., and R. Salz, "A Universally
              Unique IDentifier (UUID) URN Namespace", RFC 4122, July
              2005.



Behringer, et al.        Expires August 24, 2015               [Page 13]


Internet-Draft                     ACP                     February 2015


   [RFC4193]  Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
              Addresses", RFC 4193, October 2005.

Authors' Addresses

   Michael H. Behringer
   Cisco

   Email: mbehring@cisco.com


   Steinthor Bjarnason
   Cisco

   Email: sbjarnas@cisco.com


   Balaji BL
   Cisco

   Email: blbalaji@cisco.com


   Toerless Eckert
   Cisco

   Email: eckert@cisco.com
























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