Network Working Group                                       M. Behringer
Internet-Draft                                              S. Bjarnason
Intended status: Informational                                Balaji. BL
Expires: December 22, 2014                                     T. Eckert
                                                           June 20, 2014

                       An Autonomic Control Plane


   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 an "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

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   This Internet-Draft will expire on December 22, 2014.

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   to this document.  Code Components extracted from this document must
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Table of Contents

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

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 autonomic
   service agents in the network require a control plane which is
   independent of the network they manage, to avoid impacting their own

   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.  It therefore remains operational even in the presence of

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   configuration errors, addressing or routing issues, or where policy
   could inadvertedly affect control plane connectivity.  It serves as a
   "virtual out of band channel": An operator can use it to log into
   remote devices in such cases.  And an SDN controller 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

2.  Problem Statement

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

   o  Bootstrapping a network while devices are not yet configured.
      Bootstrapping a new device today 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
      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.

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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-bootstrapping-keyinfrastructures]
   describes how a domain certificate can be automatically and securely
   derived from a vendor specific Unique Device Identifier (UDI) or
   IDevID certificate.

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 existance of a domain

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

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

   o  Globally valid Unique devide identifier (UDI)

   o  Link Local IPv6 address

   o  Trust information

   o  Validity of the trust

   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.

3.3.  Authenticating Neighbors

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

   o  Inside the domain: If the domain certificate presented is
      validated to be in the same domain as that of the autonomic entity
      then the neighbour 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.  An ACP channel will be

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

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
   neighbour a set of parameters for establishing the communication
   channel, most notably channel type and security type.  The channel
   type could be any tunnel mechanism that is feasible between two
   adjacent neighbours, for example a GRE tunnel.  The security type
   could be any of the channel protection mechanism that is available
   between two adjacent neighbours on a given channel type, for example
   IPSEC.  The establishment of the autonomic control plane can happen
   after the channel type and security type is negotiated.

3.5.  Channel Establishment

   After authentication and capability negotiation autonomic nodes
   establish a secure channel towards their direct AN neighbours 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), using IPv6 link local
      addresses between two adjacent neighbours.  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.

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,

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   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

   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 neighbours.  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.

   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.

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.

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   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.

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

5.  Self-Protection Properties

   As explained in Section 3, the ACP is based on channels being built
   between devices which have been previously been authenticated based
   on their domain certificates.  The channels themselves are protected
   using standard encryption technologies like 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

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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
      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.  To make this possible for systems not
   supporting the ACP natively, the connection to the ACP must be
   manually established, through configuration.  [EDNOTE: More details
   to be provided in a later version of this document.]  Long term NMS

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   systems might become autonomic devices with domain certificates, and
   then automatically join 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

   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

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.

11.  Change log [RFC Editor: Please remove]

      00: Initial version.

12.  References

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              Behringer, M., Carpenter, B., and S. Jiang, "Gap Analysis
              for Autonomic Networking", draft-irtf-nmrg-an-gap-
              analysis-00 (work in progress), April 2014.

              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-00 (work in progress),
              December 2013.

              Pritikin, M., Behringer, M., and S. Bjarnason,
              "Bootstrapping Key Infrastructures", draft-pritikin-
              bootstrapping-keyinfrastructures-00 (work in progress),
              January 2014.

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

Authors' Addresses

   Michael H. Behringer


   Steinthor Bjarnason


   Balaji BL


   Toerless Eckert


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