Path Computation Element (PCE) Communication Protocol Generic Requirements
RFC 4657

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Network Working Group                                        J. Ash, Ed.
Request for Comments: 4657                                          AT&T
Category: Informational                                J.L. Le Roux, Ed.
                                                          France Telecom
                                                          September 2006

         Path Computation Element (PCE) Communication Protocol
                          Generic Requirements

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

   The PCE model is described in the "PCE Architecture" document and
   facilitates path computation requests from Path Computation Clients
   (PCCs) to Path Computation Elements (PCEs).  This document specifies
   generic requirements for a communication protocol between PCCs and
   PCEs, and also between PCEs where cooperation between PCEs is
   desirable.  Subsequent documents will specify application-specific
   requirements for the PCE communication protocol.

Table of Contents

   1. Introduction ....................................................2
   2. Conventions Used in This Document ...............................3
   3. Terminology .....................................................3
   4. Overview of PCE Communication Protocol (PCECP) ..................4
   5. PCE Communication Protocol Generic Requirements .................5
      5.1. Basic Protocol Requirements ................................5
           5.1.1. Commonality of PCC-PCE and PCE-PCE Communication ....5
           5.1.2. Client-Server Communication .........................5
           5.1.3. Transport ...........................................5
           5.1.4. Path Computation Requests ...........................5
           5.1.5. Path Computation Responses ..........................7
           5.1.6. Cancellation of Pending Requests ....................7
           5.1.7. Multiple Requests and Responses .....................8
           5.1.8. Reliable Message Exchange ...........................8
           5.1.9. Secure Message Exchange .............................9

Ash & Le Roux                Informational                      [Page 1]
RFC 4657       PCE Communication Protocol Generic Reqmnts September 2006

           5.1.10. Request Prioritization ............................10
           5.1.11. Unsolicited Notifications .........................10
           5.1.12. Asynchronous Communication ........................10
           5.1.13. Communication Overhead Minimization ...............10
           5.1.14. Extensibility .....................................11
           5.1.15. Scalability .......................................11
           5.1.16. Constraints .......................................12
           5.1.17. Objective Functions Supported .....................13
      5.2. Deployment Support Requirements ...........................13
           5.2.1. Support for Different Service Provider
                  Environments .......................................13
           5.2.2. Policy Support .....................................14
      5.3. Aliveness Detection & Recovery Requirements ...............14
           5.3.1. Aliveness Detection ................................14
           5.3.2. Protocol Recovery ..................................14
           5.3.3. LSP Rerouting & Reoptimization .....................14
   6. Security Considerations ........................................15
   7. Manageability Considerations ...................................16
   8. Contributors ...................................................17
   9. Acknowledgements ...............................................18
   10. References ....................................................19
      10.1. Normative References .....................................19
      10.2. Informative References ...................................19

1.  Introduction

   A Path Computation Element (PCE) [RFC4655] supports requests for path
   computation issued by a Path Computation Client (PCC), which may be
   'composite' (co-located) or 'external' (remote) from a PCE.  When the
   PCC is external from the PCE, a request/response communication
   protocol is required to carry the path computation request and return
   the response.  In order for the PCC and PCE to communicate, the PCC
   must know the location of the PCE; PCE discovery is described in
   [PCE-DISC-REQ].

   The PCE operates on a network graph in order to compute paths based
   on the path computation request(s) issued by the PCC(s).  The path
   computation request will include the source and destination of the
   paths to be computed and a set of constraints to be applied during
   the computation, and it may also include an objective function.  The