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