Access Node Control Protocol (ancp)

Last Modified: 2007-10-05

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
    Dec 2007  ANCP MIB Last Call
    Dec 2007  Framework and Requirements last call
    Mar 2008  Access Node Control Protocol (ANCP) Last Call
    Apr 2008  Re-charter or conclude Working Group

    Internet-Drafts:

    Framework and Requirements for an Access Node Control Mechanism in Broadband Multi-Service Networks (88791 bytes)
    Security Threats and Security Requirements for the Access Node Control Protocol (ANCP) (38042 bytes)
    Protocol for Access Node Control Mechanism in Broadband Networks (101344 bytes)
    Access Node Control Protocol (ANCP) MIB module for Access Nodes (65074 bytes)

    No Request For Comments

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