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A Backward-Recursive PCE-Based Computation (BRPC) Procedure to Compute Shortest Constrained Inter-Domain Traffic Engineering Label Switched Paths
RFC 5441

Network Working Group                                   JP. Vasseur, Ed.
Request for Comments: 5441                            Cisco Systems, Inc
Category: Standards Track                                       R. Zhang
                                                              BT Infonet
                                                                N. Bitar
                                                                 Verizon
                                                             JL. Le Roux
                                                          France Telecom
                                                              April 2009

 A Backward-Recursive PCE-Based Computation (BRPC) Procedure to Compute
         Shortest Constrained Inter-Domain Traffic Engineering
                          Label Switched Paths

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (c) 2009 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   Without obtaining an adequate license from the person(s) controlling
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   it for publication as an RFC or to translate it into languages other
   than English.

Vasseur, et al.             Standards Track                     [Page 1]
RFC 5441                          BRPC                        April 2009

Abstract

   The ability to compute shortest constrained Traffic Engineering Label
   Switched Paths (TE LSPs) in Multiprotocol Label Switching (MPLS) and
   Generalized MPLS (GMPLS) networks across multiple domains has been
   identified as a key requirement.  In this context, a domain is a
   collection of network elements within a common sphere of address
   management or path computational responsibility such as an IGP area
   or an Autonomous Systems.  This document specifies a procedure
   relying on the use of multiple Path Computation Elements (PCEs) to
   compute such inter-domain shortest constrained paths across a
   predetermined sequence of domains, using a backward-recursive path
   computation technique.  This technique preserves confidentiality
   across domains, which is sometimes required when domains are managed
   by different service providers.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Requirements Language  . . . . . . . . . . . . . . . . . .  4
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  General Assumptions  . . . . . . . . . . . . . . . . . . . . .  5
   4.  BRPC Procedure . . . . . . . . . . . . . . . . . . . . . . . .  5
     4.1.  Domain Path Selection  . . . . . . . . . . . . . . . . . .  6
     4.2.  Mode of Operation  . . . . . . . . . . . . . . . . . . . .  6
   5.  PCEP Protocol Extensions . . . . . . . . . . . . . . . . . . .  8
   6.  VSPT Encoding  . . . . . . . . . . . . . . . . . . . . . . . .  9
   7.  Inter-AS TE Links  . . . . . . . . . . . . . . . . . . . . . . 10
   8.  Usage in Conjunction with Per-Domain Path Computation  . . . . 10
   9.  BRPC Procedure Completion Failure  . . . . . . . . . . . . . . 10
   10. Applicability  . . . . . . . . . . . . . . . . . . . . . . . . 11
     10.1. Diverse End-to-End Path Computation  . . . . . . . . . . . 11
     10.2. Path Optimality  . . . . . . . . . . . . . . . . . . . . . 12
   11. Reoptimization of an Inter-Domain TE LSP . . . . . . . . . . . 12
   12. Path Computation Failure . . . . . . . . . . . . . . . . . . . 12
   13. Metric Normalization . . . . . . . . . . . . . . . . . . . . . 12
   14. Manageability Considerations . . . . . . . . . . . . . . . . . 13
     14.1. Control of Function and Policy . . . . . . . . . . . . . . 13

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