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A Path Computation Element (PCE)-Based Architecture
RFC 4655

Document type: RFC - Informational (August 2006; No errata)
Document stream: IETF
Last updated: 2013-03-02
Other versions: plain text, pdf, html

IETF State: (None)
Consensus: Unknown
Document shepherd: No shepherd assigned

IESG State: RFC 4655 (Informational)
Responsible AD: Ross Callon
Send notices to: pce-chairs@tools.ietf.org

Network Working Group                                          A. Farrel
Request for Comments: 4655                            Old Dog Consulting
Category: Informational                                    J.-P. Vasseur
                                                     Cisco Systems, Inc.
                                                                  J. Ash
                                                                    AT&T
                                                             August 2006

          A Path Computation Element (PCE)-Based Architecture

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   Constraint-based path computation is a fundamental building block for
   traffic engineering systems such as Multiprotocol Label Switching
   (MPLS) and Generalized Multiprotocol Label Switching (GMPLS)
   networks.  Path computation in large, multi-domain, multi-region, or
   multi-layer networks is complex and may require special computational
   components and cooperation between the different network domains.

   This document specifies the architecture for a Path Computation
   Element (PCE)-based model to address this problem space.  This
   document does not attempt to provide a detailed description of all
   the architectural components, but rather it describes a set of
   building blocks for the PCE architecture from which solutions may be
   constructed.

Table of Contents

   1. Introduction ....................................................3
   2. Terminology .....................................................3
   3. Definitions .....................................................4
   4. Motivation for a PCE-Based Architecture .........................6
      4.1. CPU-Intensive Path Computation .............................6
      4.2. Partial Visibility .........................................7
      4.3. Absence of the TED or Use of Non-TE-Enabled IGP ............7
      4.4. Node Outside the Routing Domain ............................8

Farrel, et al.               Informational                      [Page 1]
RFC 4655                    PCE Architecture                 August 2006

      4.5. Network Element Lacks Control Plane or Routing Capability ..8
      4.6. Backup Path Computation for Bandwidth Protection ...........8
      4.7. Multi-layer Networks .......................................9
      4.8. Path Selection Policy ......................................9
      4.9. Non-Motivations ...........................................10
           4.9.1. The Whole Internet .................................10
           4.9.2. Guaranteed TE LSP Establishment ....................10
   5. Overview of the PCE-Based Architecture .........................11
      5.1. Composite PCE Node ........................................11
      5.2. External PCE ..............................................12
      5.3. Multiple PCE Path Computation .............................13
      5.4. Multiple PCE Path Computation with Inter-PCE
           Communication .............................................14
      5.5. Management-Based PCE Usage ................................15
      5.6. Areas for Standardization .................................16
   6. PCE Architectural Considerations ...............................16
      6.1. Centralized Computation Model .............................16
      6.2. Distributed Computation Model .............................17
      6.3. Synchronization ...........................................17
      6.4. PCE Discovery and Load Balancing ..........................18
      6.5. Detecting PCE Liveness ....................................20
      6.6. PCC-PCE and PCE-PCE Communication .........................20
      6.7. PCE TED Synchronization ...................................22
      6.8. Stateful versus Stateless PCEs ............................23
      6.9. Monitoring ................................................25
      6.10. Confidentiality ..........................................25
      6.11. Policy ...................................................26
           6.11.1. PCE Policy Architecture ...........................26
           6.11.2. Policy Realization ................................28
           6.11.3. Type of Policies ..................................28
           6.11.4. Relationship to Signaling .........................29
      6.12. Unsolicited Interactions .................................30
      6.13. Relationship with Crankback ..............................30
   7. The View from the Path Computation Client ......................31
   8. Evaluation Metrics .............................................32

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