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Path Computation Element (pce) (WG)

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Routing Area Director(s):

Routing Area Advisor:


Meeting Slides


Request for Comments:

Charter (as of 2010-07-09)

The PCE Working Group is chartered to specify a Path Computation Element
(PCE) based architecture for the computation of paths for MPLS and GMPLS
Point to Point and Point to Multi-point 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
- 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
- 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
Done  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
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
Done  Submit PCE communication protocol specification to the IESG to be considered as a Proposed Standard
Jun 2008  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 PCE P2MP communication requirements
Done  Submit first draft of the PCE P2MP PCEP protocol extensions
Done  Submit PCE P2MP communication requirements to the IESG to be considered as an Informational RFC
Nov 2008  Submit applicability statement to the IESG as informational RFC
Done  Submit PCE P2MP PCEP protocol extensions to the IESG to be considered as an Proposed Standard RFC
Feb 2009  Submit the PCE MIB Internet-Draft to the IESG for consideration as Proposed Standard
Done  Submit applicability and metrics documents to the IESG
Feb 2009  Evaluate WG progress, recharter or close