To: Mr. Yoichi Maeda, chairman ITU-T Study Group 15 Cc: Mr. Scott Bradner, IETF liaison coordinator with the ITU-T Alex Zinin and Bill Fenner, IETF Routing Area Directors From: Adrian Farrel and JP Vasseur, IETF PCE working group chairs Subject: Path Computation Element Working Group in the IETF For: Action Deadline: 1st April 2005 Dear Mr. Maeda, We would like to inform you and Study Group 15 of the creation of a new working group within the IETF to work on the Path Computation Element (PCE). The charter of this working group is shown below and provides a brief definition of the PCE. Further understanding of what the IETF means by PCE can be found in http://www.ietf.org/internet-drafts/draft-ash-pce-architecture-01.txt although this should be seen as a work in progress. We believe that some work may already have been carried out within the ITU-T (probably within SG15) on determining a functional architecture for a similar logical entity - that is, for a logically distinct control plane component that is responsible for performing path computations. We are anxious to leverage this work so that we can produce a solution that most closely matches the needs of the ITU-T community, so that we do not waste effort re-inventing anything, and so that we can move our own work forwards as rapidly as possible. Could you please pass this liaison to all interested parties within the ITU-T and particularly to the Questions that may have worked on a similar topic with a request that they give us pointers to all related and previous work. Once we have established direct contact with the relevant groups we will continue to liaise our progress to them and will solicit their opinions especially with respect to architecture and functional requirements. Thank you for your help. Best regards, Adrian Farrel and JP Vasseur ===== Path Computation Element Working Group Charter 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 obustness 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: Feb 05 Submit first draft of PCE architecture document Feb 05 Submit first draft of PCE discovery requirements and protocol extensions documents Apr 05 Submit first draft of the PCE communication protocol requirements May 05 Submit first draft of the definition of objective metrics Jul 05 Submit first draft of the PCE communication protocol specification Aug 05 Submit PCE architecture specification to the IESG to be considered as Informational RFC Nov 05 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) Nov 05 Submit first draft of the MIB module for the PCE protocol Dec 05 Submit PCE communication protocol requirements to the IESG to be considered as an Informational RFC Dec 05 Submit PCE discovery protocol extensions specifications to the IESG to be considered as a Proposed Standard Dec 05 Submit PCE communication protocol specification to the IESG to be considered as a Proposed Standard Feb 06 Submit the applicability and metrics documents to the IESG to be considered as Informational RFC Feb 06 Evaluate WG progress, recharter or close