ANIMA WG                                               M. Behringer, Ed.
Internet-Draft                                              S. Bjarnason
Intended status: Standards Track                              Balaji. BL
Expires: April 8, 2016                                         T. Eckert
                                                           Cisco Systems
                                                         October 6, 2015

                       An Autonomic Control Plane


   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.

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   This Internet-Draft will expire on April 8, 2016.

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   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   ( 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  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Use Cases for an Autonomic Control Plane  . . . . . . . . . .   4
     2.1.  An Infrastructure for Autonomic Functions . . . . . . . .   4
     2.2.  Secure Bootstrap over an Unconfigured Network . . . . . .   4
     2.3.  Data Plane Independent Permanent Reachability . . . . . .   5
   3.  Requirements  . . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   6
   5.  Self-Creation of an Autonomic Control Plane . . . . . . . . .   8
     5.1.  Preconditions . . . . . . . . . . . . . . . . . . . . . .   8
     5.2.  Candidate ACP Neighbor Selection  . . . . . . . . . . . .   8
     5.3.  Capability Negotiation  . . . . . . . . . . . . . . . . .   9
     5.4.  Channel Establishment . . . . . . . . . . . . . . . . . .   9
     5.5.  Context Separation  . . . . . . . . . . . . . . . . . . .  10
     5.6.  Addressing inside the ACP . . . . . . . . . . . . . . . .  10
     5.7.  Routing in the ACP  . . . . . . . . . . . . . . . . . . .  12
   6.  Workarounds for Non-Autonomic Nodes . . . . . . . . . . . . .  12
     6.1.  Connecting a Non-Autonomic Controller / NMS system  . . .  12
     6.2.  ACP through Non-Autonomic L3 Clouds . . . . . . . . . . .  13
   7.  The Negotiation Protocol  . . . . . . . . . . . . . . . . . .  13
   8.  The Channel Type  . . . . . . . . . . . . . . . . . . . . . .  13
   9.  Self-Healing Properties . . . . . . . . . . . . . . . . . . .  14
   10. Self-Protection Properties  . . . . . . . . . . . . . . . . .  15
   11. The Administrator View  . . . . . . . . . . . . . . . . . . .  15
   12. Security Considerations . . . . . . . . . . . . . . . . . . .  16
   13. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  16
   14. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  16
   15. Change log [RFC Editor: Please remove]  . . . . . . . . . . .  17
     15.1.  Initial version  . . . . . . . . . . . . . . . . . . . .  17
     15.2.  draft-behringer-anima-autonomic-control-plane-00 . . . .  17
     15.3.  draft-behringer-anima-autonomic-control-plane-01 . . . .  17
     15.4.  draft-behringer-anima-autonomic-control-plane-02 . . . .  17
     15.5.  draft-behringer-anima-autonomic-control-plane-03 . . . .  18
     15.6.  draft-ietf-anima-autonomic-control-plane-00  . . . . . .  18
     15.7.  draft-ietf-anima-autonomic-control-plane-01  . . . . . .  18
   16. References  . . . . . . . . . . . . . . . . . . . . . . . . .  19
   Appendix A.  Background on the choice of routing protocol . . . .  20
   Appendix B.  Alternative: An ACP without Separation . . . . . . .  21
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  22

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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.behringer-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.
   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.

   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.behringer-anima-reference-model].  For example, GRASP
      [I-D.ietf-anima-grasp] can run inside the ACP.

   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

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      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

   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, Section 7 defines the
   negotiation protocol, and Section 8 the first channel types for the

   The document "Autonomic Network Stable Connectivity"
   [I-D.eckert-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

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.

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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

   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.

   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

   The document "Autonomic Network Stable Connectivity"
   [I-D.eckert-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:

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   1.  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.

   2.  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).

   3.  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.

   4.  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.

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

   The 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 end-to-end connectivity in some cases,
   for example to provide an end-to-end security association for some
   protocols.  This is possible, but then has a dependency on routable
   address space.

4.  Overview

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

   o  An autonomic node creates a virtual routing and forwarding (VRF)
      instance, or a similar virtual context.

   o  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.  Intent can override this default policy.

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

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   o  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.

   o  Inside the ACP VRF, each node sets up a virtual interface with its
      ULA IPv6 address.

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

   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.

           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.

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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:

   o  A globally unique domain certificate, with which it can
      cryptographically assert its membership of the domain.  The
      document [I-D.ietf-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].)

   o  An adjacency table, which contains information about adjacent
      autonomic nodes, at a minimum: node-ID, IP address, domain,
      certificate.  An autonomic device maintains this adjacency table
      up to date.  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.  Candidate ACP Neighbor Selection

   An autonomic node must determine to which other autonomic nodes in
   the adjacency table it should build an ACP connection.

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

   Intent can change this default behaviour.  The precise format for
   this Intent needs to be defined outside this document.  Example
   Intent policies are:

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

   o  Two domains should build one single ACP between themselves, for
      example "" should establish the ACP also with nodes
      from "".  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

5.3.  Capability Negotiation

   Autonomic devices may have different capabilities based on the type
   of device, OS version, etc.  To establish a trusted secure ACP
   channel, devices must first negotiate their mutual capabilities in
   the data plane.  This allows for the support of different channel
   types in the future.

   For each node on the candidate ACP neighbor list, capabilities need
   to be exchanged.  The capability negotiation is based on GRASP
   [I-D.ietf-anima-grasp].  The relevant protocol details are defined in
   Section 7.  This negotiation MUST be secure: The identity of the
   other node MUST be validated during capability negotiation, and the
   exchange MUST be authenticated.

   The first parameter to be negotiated is the ACP Channel type.  The
   channel types are defined in Section 8.  Other parameters may be
   added later.

   Intent may also influence the capability negotiation.  For example,
   Intent may require a minimum ACP tunnel security.  This is outside
   scope for this document.

5.4.  Channel Establishment

   After authentication and capability negotiation autonomic nodes
   establish a secure channel towards the AN neighbors with the above
   negotiated parameters.

   The channel establishment MUST be authenticated.  Whether or not, and
   how, a channel is encrypted is part of the capability negotiation,
   potentially controlled by Intent.

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   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
   decrypts incoming traffic from the ACP, and encrypts outgoing traffic
   to its neighbors in the ACP.  Routing is discussed in Section 5.7.

   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.

5.5.  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.  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.

   [EDNOTE: Previous versions of this document also discussed an option
   where the ACP runs in the data plane without logical separation.
   Consensus is to focus only on the separated ACP now, and to remove
   the ACP in the data plane from this document.  See Appendix B for the
   reasons for this decision.]

5.6.  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

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   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 5.5.

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

   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.

   Once an autonomic node is enrolled in a domain, it automatically
   creates a network wide Unique Local Addresses (ULA) in accordance
   with [RFC4193] with the following algorithm:

   o  Prefix FD00::/8, defining locally assigned unique local addresses.
      See Section 3.1 of [RFC4193].

   o  Global ID: an MD5 hash of the domain ID, using the 40 least
      significant bits.  This results in a pseudo-random global ID, in
      accordance with Section 3.2 of [RFC4193].

   o  Subnet ID and interface ID:
      [I-D.behringer-anima-autonomic-addressing] defines how these
      fields can be constructed and used.

   With this algorithm, 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 9 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.

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5.7.  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 [RFC6550] as one such
   protocol which is light weight and scales well for the control plane
   traffic.  See Appendix A for more details on the choice of RPL.

6.  Workarounds for Non-Autonomic Nodes

6.1.  Connecting a Non-Autonomic 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, 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.  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 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.

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   The non-autonomic NMS host must be routed in the ACP.  This involves
   two parts: 1) the NMS host must point default to the AN device 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

   The document "Autonomic Network Stable Connectivity"
   [I-D.eckert-anima-stable-connectivity] explains in more detail how
   the ACP can be integrated in a mixed NOC environment.

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

7.  The Negotiation Protocol

   This section describes the negotiation exchange in detail.  It is
   based on GRASP [I-D.ietf-anima-grasp].  Since at the time of
   establishing the ACP channel there is obviously no ACP yet, this
   negotiation protocol must run in the data plane.  This negotiation
   MUST be authenticated, to avoid downgrade attackes, where an attacker
   injects bogus negotiation messages demanding a less secure ACP
   channel type.  The negotiation MAY be encrypted.

   [The detailed negotiation flow and mapping into GRASP messages is to
   be completed.]

8.  The Channel Type

   Two adjacent nodes negotiate an ACP channel.  This channel MUST be
   authenticated and SHOULD be encrypted.

   The nodes negotiate a parameter called "ACP channel type".  This
   document defines a single, MUST implement channel type: GRE with

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   IPsec transport mode.  See IANA Considerations (Section 13) for the
   formal definition of this parameter.

9.  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
   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 5.6).

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10.  Self-Protection Properties

   As explained in Section 5, 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

11.  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

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   cannot connect to an ACP.  See Section 6.1 for more details on how to
   connect an NMS host into the ACP.

12.  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

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

   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.

   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

13.  IANA Considerations

   Section 8 describes an option for the channel negotiation, the
   channel type.  We request IANA to create a registry for ACP channel

   The ACP channel type is a 8-bit unsigned integer.  This document only
   assigns the first value.

        Number | Channel Type                      | RFC
            0  | GRE tunnel protected with         | this document
               | IPsec transport mode              |
        1-255  | reserved for future channel types |

14.  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

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   Clemm, Yves Hertoghs, Bruno Klauser, Max Pritikin, Ravi Kumar

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

15.  Change log [RFC Editor: Please remove]

15.1.  Initial version

   First version of this document:

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

   Initial version of the anima document; only minor edits.

15.3.  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

15.4.  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

   o  Clarified the relationship with draft-eckert-anima-stable-

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15.5.  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.

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

   No changes; re-submitted as WG document.

15.7.  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

   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.

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   o  Updated links, lots of small edits.

16.  References

              Behringer, M., "An Autonomic IPv6 Addressing Scheme",
              draft-behringer-anima-autonomic-addressing-01 (work in
              progress), June 2015.

              Behringer, M., Carpenter, B., Eckert, T., Ciavaglia, L.,
              Liu, B., Jeff, J., and J. Strassner, "A Reference Model
              for Autonomic Networking", draft-behringer-anima-
              reference-model-03 (work in progress), June 2015.

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

              Eckert, T. and M. Behringer, "Using Autonomic Control
              Plane for Stable Connectivity of Network OAM", draft-
              eckert-anima-stable-connectivity-01 (work in progress),
              March 2015.

              Pritikin, M., Richardson, M., Behringer, M., and S.
              Bjarnason, "Bootstrapping Key Infrastructures", draft-
              ietf-anima-bootstrapping-keyinfra-00 (work in progress),
              August 2015.

              Carpenter, B. and B. Liu, "A Generic Autonomic Signaling
              Protocol (GRASP)", draft-ietf-anima-grasp-00 (work in
              progress), August 2015.

   [RFC4122]  Leach, P., Mealling, M., and R. Salz, "A Universally
              Unique IDentifier (UUID) URN Namespace", RFC 4122,
              DOI 10.17487/RFC4122, July 2005,

   [RFC4193]  Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
              Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005,

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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,

   [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,

   [RFC7576]  Jiang, S., Carpenter, B., and M. Behringer, "General Gap
              Analysis for Autonomic Networking", RFC 7576,
              DOI 10.17487/RFC7576, June 2015,

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:

   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

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      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.

   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.  Alternative: An ACP without Separation

   Section 5 explains how the ACP is constructed as a virtually
   separated overlay network.  An alternative ACP design can be achieved
   without the VRFs.  In this case, the autonomic virtual addresses are
   part of the data plane, and subject to routing, filtering, QoS, etc
   on the data plane.  The secure tunnels are in this case used by
   traffic to and from the autonomic address space.  They are still

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   required to provide the authentication function for all autonomic

   At IETF 93 in Prague, the suggestion was made to not advance with the
   data plane ACP, and only continue with the virtually separate ACP.
   The reason for this decision is that the contextual separation of the
   ACP provides a range of benefits (more robustness, less potential
   interactions with user configurations), while it is not much harder
   to achieve.

   This appendix serves to explain the decision; it will be removed in
   the next version of the draft.

Authors' Addresses

   Michael H. Behringer (editor)
   Cisco Systems
   Building D, 45 Allee des Ormes
   Mougins  06250


   Steinthor Bjarnason
   Cisco Systems


   Balaji BL
   Cisco Systems


   Toerless Eckert
   Cisco Systems


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