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Shepherd writeup

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?  Is this type of RFC indicated in the
title page header?

Proposed Standard, which is 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 authentication framework for the Session Initiation Protocol (SIP, RFC
3261) closely parallels that of the Hypertext Transfer Protocol (HTTP) Digest
Access Authentication (RFC 2617). RFC 2617 was obsoleted by RFC 7616, which
introduces more secure digest algorithms (e.g., SHA-256 and SHA-512-256). This
document updates the authentication scheme used by SIP to add support for these
more secure algorithms that are listed in the "Hash Algorithms for HTTP Digest
Authentication" registry created by RFC 7616. Although the MD5 algorithm is
considered cryptographically broken, it is still supported for backward

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

Work on this topic (initially as draft-yusef-sipcore-digest-scheme) started in
January 2014, somewhat in parallel with the HTTP Digest Access Authentication
work [RFC7616]. The SIPCORE participants who voiced an opinion thought it was a
good idea, and provided careful reviews. The draft went through multiple
iterations as feedback was incorporated. There was no pushback against the
concept on-list; however, at the London IETF 89 SIPCORE WG session, it was
discussed that SIP authentication in general needed an overhaul, not just the
digest scheme. While some work went into that effort, both the new work and
draft-yusef-sipcore-digest-scheme expired about six months later. In 2017 the
author resurrected the draft, and again the draft received support and
feedback, but then the draft expired later in the year. It was resurrected
again in spring 2019, and adopted as a WG item.

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?

The content of this document has been implemented and deployed in mobile IMS
networks. Several reviewers provided substantial feedback and they have been
thanked in the Acknowledgments section. The content of the document does not
require expert review.


  Who is the Document Shepherd? Who is the Responsible Area

Document Shepherd: Jean Mahoney
Responsible Area Director: Adam Roach

(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.

Document Shepherd went through the mail archives back to 2014 to ensure that
feedback was addressed. She considers the draft ready to proceed.

(4) Does the document Shepherd have any concerns about the depth or
breadth of the reviews that have been performed?

The Document Shepherd is satisfied with the breadth and depth of reviews
performed by the working group.

(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.

None required.

(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 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.

The author has confirmed conformance with BCPs 78 and 79.

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

No disclosure has been filed.

(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?

The only pushback this document has received has been at IETF 89 in 2014, when
the WG wanted to solve a bigger problem. Otherwise it has received WG support
and careful review.

(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 one has indicated any discontent with the draft.

(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

idnits 2.16.02 was run, and no issues were found. The Shepherd checked the
draft against No issues were
found with the draft.

(12) Describe how the document meets any required formal review
criteria, such as the MIB Doctor, media type, and URI type reviews.

No formal review needed.

(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?

All normative references are to published RFCs.

(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.

There are no downward normative references.

(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.

This document updates RFC 3261. This information is clearly captured in the
header, abstract, and introduction.

(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 Considerations section of this document merely points to the registry
that RFC 7616 created and specifies that algorithms defined in that registry
may be used in SIP digest authentication. It does not create nor modify any
IANA registry, and thus has no actions for IANA.

(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.

This document does not create any new IANA 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.

The document makes two small changes to the ABNF of SIP [RFC3261]. The working
group provided feedback on the ABNF. The Doc Shepherd inspected the ABNF
manually and found no issues.