> As required by RFC 4858, this is the current template for the Document
> Shepherd Write-Up.
> Changes are expected over time. This version is dated 24 February 2012.
> (1) What type of RFC is being requested (BCP, Proposed Standard,
> Internet Standard, Informational, Experimental, or Historic)?
> Why is this the proper type of RFC?
This is an architecture document. It discusses the architecture for PCE as
a central controller.
> Is this type of RFC indicated in the title page header?
> (2) The IESG approval announcement includes a Document Announcement
> Write-Up. Please provide such a Document Announcement Write-Up. Recent
> examples can be found in the "Action" announcements for approved
> documents. The approval announcement contains the following sections:
> Technical Summary
> Relevant content can frequently be found in the abstract
> and/or introduction of the document. If not, this may be
> an indication that there are deficiencies in the abstract
> or introduction.
The Path Computation Element (PCE) has become established as a core
component of Software Defined Networking (SDN) systems. It can
compute optimal paths for traffic across a network for any definition
of "optimal" and can also monitor changes in resource availability
and traffic demands to update the paths.
Conventionally, the PCE has been used to derive paths for MPLS Label
Switched Paths (LSPs). These paths are supplied using the Path
Computation Element Communication Protocol (PCEP) to the head end of
the LSP for signaling in the MPLS network.
SDN has a far broader applicability than just signaled MPLS traffic
engineered networks, and the PCE may be used to determine paths in a
wide range of use cases including static LSPs, segment routing,
service function chaining (SFC), and indeed any form of routed or
switched network. It is, therefore, reasonable to consider PCEP as a
general southbound control protocol for use in these environments to
allow the PCE to be fully enabled as a central controller.
This document briefly introduces the architecture for PCE as a
central controller, examines the motivations and applicability for
PCEP as a southbound interface, and introduces the implications for
the protocol. This document does not describe the use cases in
detail and does not define protocol extensions: that work is left for
> Working Group Summary
> Was there anything in WG process that is worth noting? For
> example, was there controversy about particular points or
> were there decisions where the consensus was particularly
The progress of the document through the WG has been smooth.
There was some serious debate before the last call with regards
to implications on manageability and on PCEP. The authors addressed
all of these concerns by adding relevant text to the document.
> Document Quality
> Are there existing implementations of the protocol? Have a
> significant number of vendors indicated their plan to
> implement the specification? Are there any reviewers that
> merit special mention as having done a thorough review,
> e.g., one that resulted in important changes or a
> conclusion that the document had no substantive issues? If
> there was a MIB Doctor, Media Type or other expert review,
> what was its course (briefly)? In the case of a Media Type
> review, on what date was the request posted?
This document has been discussed and reviewed thoroughly by the WG.
The base PCE architecture and the PCEP protocol have been implemented.
The document that discusses the use-cases for PCE as a central controller
is actively being worked on. While there have been no public statements
on implementation of this new architecture, the authors are from multiple
vendors, and implementation is expected.
> Who is the Document Shepherd?
Vishnu Pavan Beeram
> Who is the Responsible Area Director?
> (3) Briefly describe the review of this document that was performed by
> the Document Shepherd. If this version of the document is not ready
> for publication, please explain why the document is being forwarded to
> the IESG.
The Document Shepherd has reviewed the document as part of normal WG progress
and WG last call. The Shepherd believes this document is ready for publication.
> (4) Does the document Shepherd have any concerns about the depth or
> breadth of the reviews that have been performed?
> (5) Do portions of the document need review from a particular or from
> broader perspective, e.g., security, operational complexity, AAA, DNS,
> DHCP, XML, or internationalization?
> If so, describe the review that took place.
> (6) Describe any specific concerns or issues that the Document Shepherd
> has with this document that the Responsible Area Director and/or the
> IESG should be aware of? For example, perhaps he or she is uncomfortable
> with certain parts of the document, or has concerns whether there really
> is a need for it. In any event, if the WG has discussed those issues and
> has indicated that it still wishes to advance the document, detail those
> concerns here.
No specific concerns.
> (7) Has each author confirmed that any and all appropriate IPR
> disclosures required for full conformance with the provisions of BCP 78
> and BCP 79 have already been filed. If not, explain why.
Yes, see thread
> (8) Has an IPR disclosure been filed that references this document?
> If so, summarize any WG discussion and conclusion regarding the IPR
No IPR disclosed.
> (9) How solid is the WG consensus behind this document? Does it
> represent the strong concurrence of a few individuals, with others
> being silent, or does the WG as a whole understand and agree with it?
Solid among those who are interested. "strong concurrence of a few
individuals, with others being silent" is a reasonable
> (10) Has anyone threatened an appeal or otherwise indicated extreme
> discontent? If so, please summarise the areas of conflict in separate
> email messages to the Responsible Area Director. (It should be in a
> separate email because this questionnaire is publicly available.)
No discontent seen.
> (11) Identify any ID nits the Document Shepherd has found in this
> document. (See http://www.ietf.org/tools/idnits/ and the Internet-Drafts
> Checklist). Boilerplate checks are not enough; this check needs to be
The document passes ID nits.
> (12) Describe how the document meets any required formal review
> criteria, such as the MIB Doctor, media type, and URI type reviews.
> (13) Have all references within this document been identified as
> either normative or informative?
> (14) Are there normative references to documents that are not ready for
> advancement or are otherwise in an unclear state? If such normative
> references exist, what is the plan for their completion?
> (15) Are there downward normative references references (see RFC 3967)?
> If so, list these downward references to support the Area Director in
> the Last Call procedure.
> (16) Will publication of this document change the status of any
> existing RFCs? Are those RFCs listed on the title page header, listed
> in the abstract, and discussed in the introduction? If the RFCs are not
> listed in the Abstract and Introduction, explain why, and point to the
> part of the document where the relationship of this document to the
> other RFCs is discussed. If this information is not in the document,
> explain why the WG considers it unnecessary.
> (17) Describe the Document Shepherd's review of the IANA considerations
> section, especially with regard to its consistency with the body of the
> document. Confirm that all protocol extensions that the document makes
> are associated with the appropriate reservations in IANA registries.
> Confirm that any referenced IANA registries have been clearly
> identified. Confirm that newly created IANA registries include a
> detailed specification of the initial contents for the registry, that
> allocations procedures for future registrations are defined, and a
> reasonable name for the new registry has been suggested (see RFC 5226).
The IANA section was fully reviewed by the document shepherd and is
appropriate for this draft.
> (18) List any new IANA registries that require Expert Review for future
> allocations. Provide any public guidance that the IESG would find
> useful in selecting the IANA Experts for these new registries.
> (19) Describe reviews and automated checks performed by the Document
> Shepherd to validate sections of the document written in a formal
> language, such as XML code, BNF rules, MIB definitions, etc.