Access Node Control Protocol (ancp)
-----------------------------------

Charter
Last Modified: 2007-10-05

Current Status: Active Working Group

Chair(s):
    Wojciech Dec  <[email protected]>
    Matthew Bocci  <[email protected]>

Internet Area Director(s):
    Jari Arkko  <[email protected]>
    Mark Townsley  <[email protected]>

Internet Area Advisor:
    Mark Townsley  <[email protected]>

Technical Advisor(s):
    Dan Romascanu  <[email protected]>

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    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:

Posted Revised         I-D Title   <Filename>
------ ------- --------------------------------------------
Oct 2006 Nov 2007   <draft-ietf-ancp-framework-04.txt>
               Framework and Requirements for an Access Node Control Mechanism
               in Broadband Multi-Service Networks

Jan 2007 Oct 2007   <draft-ietf-ancp-security-threats-03.txt>
               Security Threats and Security Requirements for the Access Node
               Control Protocol (ANCP)

Mar 2007 Nov 2007   <draft-ietf-ancp-protocol-02.txt>
               Protocol for Access Node Control Mechanism in Broadband
               Networks

Jun 2007 Nov 2007   <draft-ietf-ancp-mib-an-01.txt>
               Access Node Control Protocol (ANCP) MIB module for Access Nodes

Request For Comments:

 None to date.