An In-Band Data Communication Network For the MPLS Transport Profile
RFC 5718

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Internet Engineering Task Force (IETF)                         D. Beller
Request for Comments: 5718                                Alcatel-Lucent
Category: Standards Track                                      A. Farrel
ISSN: 2070-1721                                       Old Dog Consulting
                                                            January 2010

  An In-Band Data Communication Network For the MPLS Transport Profile

Abstract

   The Generic Associated Channel (G-ACh) has been defined as a
   generalization of the pseudowire (PW) associated control channel to
   enable the realization of a control/communication channel that is
   associated with Multiprotocol Label Switching (MPLS) Label Switched
   Paths (LSPs), MPLS PWs, MPLS LSP segments, and MPLS sections between
   adjacent MPLS-capable devices.

   The MPLS Transport Profile (MPLS-TP) is a profile of the MPLS
   architecture that identifies elements of the MPLS toolkit that may be
   combined to build a carrier-grade packet transport network based on
   MPLS packet switching technology.

   This document describes how the G-ACh may be used to provide the
   infrastructure that forms part of the Management Communication
   Network (MCN) and a Signaling Communication Network (SCN).
   Collectively, the MCN and SCN may be referred to as the Data
   Communication Network (DCN).  This document explains how MCN and SCN
   messages are encapsulated, carried on the G-ACh, and demultiplexed
   for delivery to the management or signaling/routing control plane
   components on an MPLS-TP node.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc5718.

Beller & Farrel             Standards Track                     [Page 1]
RFC 5718             DCN for MPLS Transport Profile         January 2010

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   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.

1.  Introduction

   The associated channel header (ACH) is specified in [RFC4385].  It is
   a packet header format for use on pseudowires (PWs) in order to
   identify packets used for Operations, Administration, and Maintenance
   (OAM) and similar functions.

   The use of the ACH is generalized in [RFC5586] and can be applied on
   any Multiprotocol Label Switching (MPLS) Label Switching Path (LSP).
   This is referred to as the Generic Associated Channel (G-ACh) and is
   intended to create a control/management communication channel
   associated with the LSP that can be used to carry packets used for
   OAM and similar functions (e.g., control/management plane messages).

   The purpose of a packet carried on the G-ACh is indicated by the
   value carried by the Channel Type field of the ACH and a registry of
   values is maintained by IANA ([RFC4446] and [RFC4385]).  The ACH is
   referred to in this document as the G-ACh header.

   The MPLS transport profile (MPLS-TP) is described in [MPLS-TP] and in
   [RFC5654].  MPLS-TP is the application of MPLS to construct a packet
   transport network.  It constitutes a profile of MPLS that enables
   operational models typical in transport networks, which includes
   additional OAM, survivability, and other maintenance functions not
   previously supported by MPLS.

   Label Switching Routers (LSRs) in MPLS networks may be operated using
   management protocols or control plane protocols.  Messaging in these
   protocols is normally achieved using IP packets exchanged over IP-
   capable interfaces.  However, some nodes in MPLS-TP networks may be
   constructed without support for direct IP encapsulation on their
   line-side interfaces and without access to an out-of-fiber data

Beller & Farrel             Standards Track                     [Page 2]
RFC 5718             DCN for MPLS Transport Profile         January 2010

   communication network.  In order that such nodes can communicate