Subject: [Pce] WG Review: Path Computation Element (pce)

From: The IESG <[email-masked]>
Date: Thu, 23 Dec 2004 14:07:15 -0500

A new IETF working group has been proposed in the Routing Area.  The IESG 
has not made any determination as yet. The following description was 
submitted, and is provided for informational purposes only. Please send 
your comments to the IESG mailing list ([email-masked]) by December 30th.

+++

Path Computation Element (pce)
================================

Current Status: Proposed Working Group

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 (OSPF, ISIS and 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.

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