Shepherd writeup

Shepherd writeup for draft-ietf-sipcore-6665-clarification-00:

[This is based on the template version 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?  Is this type of RFC indicated in the
title page header?

  This document is marked as Standards Track in the title page header,
  and that seems appropriate, because it is clarifying normative
  behavior in RFC6665, that is itself standards track. 

(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

  Experience since the publication of the most recent SIP Events
  framework (RFC6665) has shown that there is room for interpretation
  around the use of Globally Routable User Agent URIs in that 
  specification.  This document clarifies the intended behavior.

Working Group Summary

 Context: The base SIP specification (RFC3261) introduced (implicitly) the notion of dialog reuse - multiple "usages" of a dialog. For instance, an INVITE usage combined with an event subscription, or multiple event subscriptions. The SIP REFER mechanism (RFC3515) provides a widely used mechanism that creates *implicit* SUBSCRIBE/NOTIFY dialog usages. When used within an INVITE dialog (as it typically is) it causes dialog reuse.

 Unfortunately the dialog reuse concept was "half baked", and issues arose around it as it was implemented. This was discussed by RFC5057, recommending that such multiple usages be avoided. RFC5627 added the GRUU mechanism to SIP, providing a way to avoid many instances of dialog sharing. But GRUUs have been controversial - they are complex and far from universally implemented/deployed. A draft (draft-kaplan-dispatch-gruu-problematic-00) raised specific issues with deployment of GRUUs, but that draft expired without having reached consensus. It suggested that GRUUs not be used, and that other mechanisms be used to get around the need for them. But there has been no further work proposed on this since 2011.

 The elephant in the room is that there are many deployments that still don't provide GRUUs, and don't intend to do so. Some continue to seek ways that they can be compliant with RFC6665 and yet still avoid implementing GRUU, by arranging their feature implementations to carefully avoid any usage that would require them to do so. 

 Nevertheless, all these issues have been aired in the WG, and there is consensus to advance this draft and the companion drafts.

Document Quality

  [Are there existing implementations of the protocol? Have a 
  significant number of vendors indicated their plan to 
  implement the specification?]

  I'm not aware of any implementations yet. 
  It is my understanding that 3GPP release 12 has a reference,
  indicating that implementations can be expected. 

  This document has been thoroughly reviewed and discussed. Everyone
  that had something to say has aired it. 


  The document shepherd is Paul Kyzivat.
  The area director is Ben Campbell.

(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 shepherd was a SIPCORE chairman during the entire period while this
  document was introduced and discussed. He has followed (and participated
  in) the discussion and reviewed the document carefully.

(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.

  In spite of the apparent consensus on this draft, there is some
  chance that those who have problems with GRUU simply intend to
  ignore this draft or pretend/actually fail to support RFC6665. 

(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.


(8) Has an IPR disclosure been filed that references this document?
If so, summarize any WG discussion and conclusion regarding the IPR


(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?   

  There is good consensus.

(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.) 


(11) Identify any ID nits the Document Shepherd has found in this
document. (See and the Internet-Drafts
Checklist). Boilerplate checks are not enough; this check needs to be

  One issue from IdNits:

  == Couldn't figure out when the document was first submitted -- there may
     comments or warnings related to the use of a disclaimer for pre-RFC5378
     work that could not be issued because of this.  Please check the Legal
     Provisions document at to determine
     if you need the pre-RFC5378 disclaimer.

  This issue is bogus for this draft.

(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?

  All references are normative, and appropriately so.

(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?


  ** EXCEPT: in intro, ref to RFC2119 should be to 6665. **
  Author has been made aware of this. Plan is to fix together with
  any AD comments.

(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).

  IANA considerations are empty, and appropriately so.

(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.