Path Computation Element (pce)
------------------------------

 Charter
 Last Modified: 2007-09-26

 Current Status: Active Working Group

 Chair(s):
     JP Vasseur  <jpv@cisco.com>
     Adrian Farrel  <adrian@olddog.co.uk>

 Routing Area Director(s):
     Ross Callon  <rcallon@juniper.net>
     David Ward  <dward@cisco.com>

 Routing Area Advisor:
     Ross Callon  <rcallon@juniper.net>

 Mailing Lists: 
     General Discussion:pce@ietf.org
     To Subscribe:      pce-request@ietf.org
         In Body:       subscribe pce
     Archive:           http://www.ietf.org/mail-archive/web/pce/

Description of Working Group:

The PCE Working Group is chartered to specify a Path Computation 
Element
(PCE) based architecture for the computation of paths for MPLS and 
GMPLS
Traffic Engineering LSPs.

In this architecture path computation does not occur on the head-end
(ingress) LSR, but on some other path computation entity that may
physically not be located on the head-end LSR.

The PCE WG will work on application of this model within a single 
domain
or within a small group of domains (where a domain is a layer, IGP area
or Autonomous System with limited visibility from the head-end LSR).
At this time, applying this model to large groups of domains such as 
the
Internet is not thought to be possible, and the PCE WG will not spend
energy on that topic.

The WG will specify a protocol for communication between LSRs (termed
Path Computation Clients - PCCs) and PCEs, and between cooperating 
PCEs.
This protocol will be capable of representing requests for path
computation including a full set of constraints, will be able to return
multiple paths, and will include security mechanisms such as
authentication and confidentiality.

The WG will determine requirements for extensions to existing routing
and signaling protocols in support of PCE discovery and signaling of
inter-domain paths. Candidate protocols for extensions are RSVP-TE,
OSPF-TE, ISIS-TE and BGP. Any necessary extensions will be produced in
collaboration with the Working Groups responsible for the protocols.

The Working Group will also work on the definition of metrics to
evaluate path quality, scalability, responsiveness and robustness of
path computation models.

Work Items:

- Functional specification of MPLS and GMPLS Traffic Engineered LSP 
path
computation models involving Path Computation Element(s). This
includes the case of computing the paths of intra and inter-domain
TE LSPs. Such path computation includes the generation of primary,
protection and recovery paths, as well as computations for
(local/global) reoptimization and load balancing. The WG will address
the inter-area (single IGP domain) scenario first. WG progress will be
evaluated before inter-AS related work is started.

- Specification of the PCE-based architecture.

- Specification of requirements and protocol extensions related to
the policy, and security aspects of PCE-based path computation 
involving
PCEs of multiple administrative entities.

- In cooperation with protocol specific Working Group (OSPF, ISIS, IDR,
MPLS, CCAMP), development of routing (OSPF, ISIS, BGP) and LSP
signaling (RSVP-TE) extensions required to support PCE-based path
computation models.

- Specification of techniques in support of PCE discovery within and
across domains. Where such techniques result in the extensions of
existing protocols (e.g., OSPF, ISIS or BGP), this work will be done in
conjunction with the appropriate WGs.

- Specification of a new communication protocol for use between a PCC
and a PCE, and between PCEs. A single protocol will be selected from
among candidates that include the existing protocols defined in other
WGs.

- Definition of objective metrics to evaluate various criteria such as
the measurement of path quality, response time, robustness and
scalability of path computation models.

Review of the document "Requirements for path computation element in
GMPLS inter-domain networks" produced by the CCAMP WG.

 Goals and Milestones:

   Done         Submit first draft of PCE architecture document 

   Done         Submit first draft of PCE discovery requirements and protocol 
                extensions documents 

   Done         Submit first draft of the PCE communication protocol 
                requirements 

   May 2005       Submit first draft of the definition of objective metrics 

   Done         Submit first draft of the PCE communication protocol 
                specification 

   Done         Submit PCE architecture specification to the IESG to be 
                considered as Informational RFC 

   Nov 2005       Submit first draft of applicability statement (describing the 
                processes and procedures for the use of the PCE architecture, 
                protocols and protocol extensions for inter-area MPLS and GMPLS 
                Traffic Engineering) 

   Done         Submit first draft of the MIB module for the PCE protocol 

   Done         Submit PCE communication protocol requirements to the IESG to 
                be considered as an Informational RFC 

   Done         Submit PCE discovery protocol extensions specifications to the 
                IESG to be considered as a Proposed Standard 

   Dec 2005       Submit PCE communication protocol specification to the IESG to 
                be considered as a Proposed Standard 

   Feb 2006       Submit the applicability and metrics documents to the 
                considered as Informational RFCIESG to be 

   Feb 2006       Evaluate WG progress, recharter or close 


 Internet-Drafts:

Posted Revised         I-D Title   <Filename>
------ ------- --------------------------------------------
Nov 2005 Jul 2007   <draft-ietf-pce-pcep-08.txt>
                Path Computation Element (PCE) communication Protocol (PCEP) 

Nov 2005 Jul 2007   <draft-ietf-pce-inter-layer-req-05.txt>
                PCC-PCE Communication and PCE Discovery Requirements for 
                Inter-Layer Traffic Engineering 

Apr 2006 Sep 2007   <draft-ietf-pce-inter-layer-frwk-05.txt>
                Framework for PCE-Based Inter-Layer MPLS and GMPLS Traffic 
                Engineering 

Aug 2006 Nov 2007   <draft-ietf-pce-policy-enabled-path-comp-03.txt>
                Policy-Enabled Path Computation Framework 

Aug 2006 Jul 2007   <draft-ietf-pce-interas-pcecp-reqs-03.txt>
                Inter-AS Requirements for the Path Computation Element 
                Communication Protocol (PCECP) 

Aug 2006 Sep 2007   <draft-ietf-pce-brpc-06.txt>
                A Backward Recursive PCE-based Computation (BRPC) procedure to 
                compute shortest inter-domain Traffic Engineering Label 
                Switched Paths 

Sep 2006 Sep 2007   <draft-ietf-pce-disco-proto-ospf-08.txt>
                OSPF Protocol Extensions for Path Computation Element (PCE) 
                Discovery 

Sep 2006 Sep 2007   <draft-ietf-pce-disco-proto-isis-08.txt>
                IS-IS Protocol Extensions for Path Computation Element (PCE) 
                Discovery 

Dec 2006 Sep 2007   <draft-ietf-pce-tc-mib-02.txt>
                Definitions of Textual Conventions for Path Computation Element 

Jan 2007 Aug 2007   <draft-ietf-pce-manageability-requirements-02.txt>
                Inclusion of Manageability Sections in PCE Working Group Drafts 

Apr 2007 Sep 2007   <draft-ietf-pce-pcep-xro-02.txt>
                Extensions to the Path Computation Element Communication 
                Protocol (PCEP) for Route Exclusions 

May 2007 Sep 2007   <draft-ietf-pce-path-key-01.txt>
                Preserving Topology Confidentiality in Inter-Domain Path 
                Computation Using a Key-Based Mechanism 

Jun 2007 Nov 2007   <draft-ietf-pce-global-concurrent-optimization-01.txt>
                Path Computation Element Communication Protocol (PCECP) 
                Requirements and Protocol Extensions In Support of Global 
                Concurrent Optimization 

Sep 2007 Sep 2007   <draft-ietf-pce-of-00.txt>
                Encoding of Objective Functions in Path Computation Element 
                (PCE) communication and discovery protocols 

Sep 2007 Sep 2007   <draft-ietf-pce-monitoring-00.txt>
                A set of monitoring tools for Path Computation Element based 
                Architecture 

Oct 2007 Oct 2007   <draft-ietf-pce-dste-00.txt>
                Diff-Serv Aware Class Type Object for Path Computation Element 
                Communication Protocol 

 Request For Comments:

  RFC   Stat Published     Title
------- -- ----------- ------------------------------------
RFC4655 I    Aug 2006    A Path Computation Element (PCE) Based Architecture 

RFC4657 I    Sep 2006    Path Computation Element (PCE) Communication Protocol 
                       Generic Requirements 

RFC4674 I    Oct 2006    Requirements for Path Computation Element (PCE) 
                       Discovery 

RFC4927 I    Jun 2007    PCE Communication Protocol (PCECP) Specific Requirements 
                       for Inter-Area Multi Protocol Label Switching (MPLS) and 
                       Generalized MPLS (GMPLS) Traffic Engineering