Access Node Control Protocol (ancp)

Last Modified: 2008-08-21

Additional information is available at tools.ietf.org/wg/ancp

Chair(s):

  • Wojciech Dec <wdec@cisco.com>

  • Matthew Bocci <matthew.bocci@alcatel-lucent.co.uk>

    Internet Area Director(s):

  • Jari Arkko <jari.arkko@piuha.net>
  • Mark Townsley <townsley@cisco.com>

    Internet Area Advisor:

  • Mark Townsley <townsley@cisco.com>

    Technical Advisor(s):

  • Dan Romascanu <dromasca@avaya.com>

    Mailing Lists:

    General Discussion: ancp@ietf.org
    To Subscribe: ancp-request@ietf.org
    In Body: In Body: subscribe your_email_address
    Archive: http://www.ietf.org/mail-archive/web/ancp/index.html

    Description of Working Group:

    Purpose:

    The purpose of the ANCP WG is to standardize an IP based Access Node
    Control Protocol (ANCP) for use in service provider Digital Subscriber
    Line (DSL) access and aggregation networks. ANCP operates between an
    Access Node (AN) and Network Access Server (NAS).

    Necessary Terminology:

    Access Node (AN) - Network device, usually located at a service
    provider central office or street cabinet, that terminates acess loop
    connections from Subscribers. In DSL, this is often referred to as a
    Digital Subscriber Line Access Multiplexer (DSLAM)

    Network Access Server (NAS) - Network device which aggregates
    multiplexedSubscriber traffic from a number of Access Nodes. The NAS
    plays a central role in per-subsciber policy enforcement and QoS.
    Often referred to as an Broadband Network Gateway (BNG) or Broadband
    Remote Access Server (BRAS). A detailed definition of the NAS is given
    in RFC2881.

    Goals:

    ANCP is intended to address the requirement for a bidirectional, IP-
    based, control protocol that operates across multiple types (i.e.,
    Ethernet, ATM) of DSL access and aggregation networks. The goal of an
    ANCP message exchange is to convey status and control information
    between one or more ANs and one or more NASs without going through
    intermediate element managers.

    The ANCP WG will address the following four use-cases:

    1. Dynamic Access Loop Attributes
    Various queuing and scheduling mechanisms are used in access networks
    to avoid congestion while dealing with multiple flows and distinct QoS
    profiles. Communicating the access-loop status, attributes and current
    DSL synchronization rate between the AN and Subscriber up to the NAS
    is desirable, particularly when the NAS is providing QoS for
    individual flows and subscribers. ANCP will provide a mechanism to
    communicate dynamic access-loop attributes from the AN to the NAS.

    2. Access Loop Configuration
    In additional to reporting Access Loop characteristics from the AN to
    the NAS, ANCP will allow a NAS to send loop-specific configuration
    information to an AN based on the results of subscriber authentication
    and authorization (e.g., after AAA responses have been received at the
    NAS).

    3. Remote Connectivity Test
    Traditional DSL access and aggregation networks employ point-to-point
    ATM circuits between the AN and NAS for each subscriber, allowing
    troubleshooting of the local loop from the NAS via ATM OAM tools. With
    the increasing deployment of Ethernet in the access and aggregation
    network, operators require consistent methods to test and troubleshoot
    connectivity for mixed Ethernet and ATM access networks (including the
    local loop). ANCP will allow a remote procedure for a local loop
    connectivity test to be triggered from the NAS with results
    communicated back to the NAS.

    4. Multicast
    When multicast replication for subscriber-bound traffic is performed at
    the AN, it offloads the network between the AN and NAS. However, a
    subscriber's policy and configuration for multicast traffic may only be
    known at the NAS. ANCP will provide a mechanism to communicate the
    necessary information exchange between the AN and NAS so as to allow
    the AN to perform subscriber bound multicast group replication in line
    with the subscriber's policy and configuration, and also allow the NAS
    to follow each subscriber's multicast group membership.

    Non-Goals:

    ANCP is an IP-based protocol that operates between the AN and NAS,
    over a DSL access and aggregation network. It will not address setup
    or configuration of circuits or connections in the access and
    aggregation network itself.

    The focus of this WG is on one very specific application space. While
    the design of the protocol must be general as to not preclude other
    uses in the future should a need arise, it is not a goal of this WG
    to address specific requirements outside of DSL access and aggregation
    networks.

    Security:

    The ANCP working group will provide a threat analysis and address the
    associated security aspects of the control protocol.

    Resiliency and Scalabilty:

    A graceful restart mechanism will be defined to enable the protocol to
    be resilient to network failures between the AN and NAS.

    Scalability at the NAS is of primary concern, as it may be aggregating
    traffic from a large number of ANs, which in turn may be serving a
    large number of Subscribers. ANCP traffic should not become a denial
    of service attack on the NAS control plane. Format of messages,
    pacing, transport over UDP or TCP, etc. will be considered with this
    in mind.

    For reasons of aggregation network scalability, some use cases require
    that aspects of NAS or AN functionality may be distributed in nodes in
    the aggregation network. In these cases, ANCP can run between these
    nodes.

    Deliverables:

    The working group will define a basic framework and requirements
    document intended for Informational publication, focusing on the four
    use-cases outlined in this charter. This document will include a
    security threat analysis and associated requirements. The WG will then
    investigate and define a solution for an IP based control protocol
    meeting these requirements.

    There are early interoperable implementations of an ANCP-like protocol
    which are based on an extended subset of the GSMPv3 protocol. This
    running code will be the the starting point for the working group
    solution, and will be abandoned only if the WG determines it is not
    adequate to meet requirements going forward.

    Coordination with other Working Groups or Organizations:

    The working group will coordinate with the ADSL MIB working group so
    the the management framewoirk and MIB modules are consistent for DSL
    access environments. The working group will re-use, as far as
    possible, standard MIB modules that have already been defined.

    The remote connectivity test use case may require coordination with
    ITU-T Ethernet OAM work, and with IEEE 802.1ag.

    Goals and Milestones:

    Done  Accept WG I-D for ANCP Framework and Requirements
    Done  Accept WG I-D for Access Node Control Protocol (ANCP)
    Done  Accept WG ID for Security Threats analysis
    Done  Accept WG I-D for ANCP MIB
    Done  Security Threats Analysis last call
    Aug 2008  ANCP MIB Last Call
    Aug 2008  Framework and Requirements last call
    Dec 2008  Access Node Control Protocol (ANCP) Last Call
    Apr 2009  Re-charter or conclude Working Group

    Internet-Drafts:

    Framework and Requirements for an Access Node Control Mechanism in Broadband Multi-Service Networks (106213 bytes)
    Security Threats and Security Requirements for the Access Node Control Protocol (ANCP) (37671 bytes)
    Protocol for Access Node Control Mechanism in Broadband Networks (102151 bytes)
    Access Node Control Protocol (ANCP) MIB module for Access Nodes (77607 bytes)

    No Request For Comments

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