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Applicability of MPLS Transport Profile for Ring Topologies
RFC 6974

Internet Engineering Task Force (IETF)                     Y. Weingarten
Request for Comments: 6974
Category: Informational                                        S. Bryant
ISSN: 2070-1721                                            Cisco Systems
                                                           D. Ceccarelli
                                                             D. Caviglia
                                                             F. Fondelli
                                                                Ericsson
                                                                M. Corsi
                                                                  Altran
                                                                   B. Wu
                                                         ZTE Corporation
                                                                  X. Dai
                                                               July 2013

      Applicability of MPLS Transport Profile for Ring Topologies

Abstract

   This document presents an applicability of existing MPLS protection
   mechanisms, both local and end-to-end, to the MPLS Transport Profile
   (MPLS-TP) in ring topologies.  This document does not propose any new
   mechanisms or protocols.  Requirements for MPLS-TP protection
   especially for protection in ring topologies are discussed in
   "Requirements of an MPLS Transport Profile" (RFC 5654) and "MPLS
   Transport Profile (MPLS-TP) Survivability Framework" (RFC 6372).
   This document discusses how most of the requirements are met by
   applying linear protection as defined in RFC 6378 in a ring topology.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   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).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see 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/rfc6974.

Weingarten, et al.            Informational                     [Page 1]
RFC 6974                       MPLS-TP RP                      July 2013

Copyright Notice

   Copyright (c) 2013 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.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Problem Statement  . . . . . . . . . . . . . . . . . . . .  3
     1.2.  Scope of the Document  . . . . . . . . . . . . . . . . . .  4
     1.3.  Terminology and Notation . . . . . . . . . . . . . . . . .  5
   2.  Point-to-Point (P2P) Ring Protection . . . . . . . . . . . . .  6
     2.1.  Wrapping . . . . . . . . . . . . . . . . . . . . . . . . .  6
     2.2.  Steering . . . . . . . . . . . . . . . . . . . . . . . . .  8
     2.3.  SPME for P2P Protection of a Ring Topology . . . . . . . . 10
       2.3.1.  Path SPME for Steering . . . . . . . . . . . . . . . . 11
       2.3.2.  Wrapping Link Protection with Segment-Based SPME . . . 12
       2.3.3.  Wrapping Node Protection . . . . . . . . . . . . . . . 13
       2.3.4.  Wrapping for Link and Node Protection  . . . . . . . . 14
     2.4.  Analysis of P2P Protection . . . . . . . . . . . . . . . . 15
       2.4.1.  Recommendations for Protection of P2P Paths
               Traversing a Ring  . . . . . . . . . . . . . . . . . . 16
   3.  Point-to-Multipoint Protection . . . . . . . . . . . . . . . . 17
     3.1.  Wrapping for P2MP LSPs . . . . . . . . . . . . . . . . . . 17
       3.1.1.  Comparison of Wrapping and ROM-Wrapping  . . . . . . . 19
       3.1.2.  Multiple Failures Comparison . . . . . . . . . . . . . 20
     3.2.  Steering for P2MP Paths  . . . . . . . . . . . . . . . . . 21
       3.2.1.  Context Labels . . . . . . . . . . . . . . . . . . . . 21
       3.2.2.  Walk-Through Using Context Labels  . . . . . . . . . . 23
   4.  Coordination Protocol  . . . . . . . . . . . . . . . . . . . . 26

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