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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. The title page shows Standards Track as the Intended Status,
which is appropriate given the impact on other standards track documents.

(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.

This specification defines a new Session Description Protocol (SDP) Grouping
Framework extension, 'BUNDLE'.  The extension can be used with the SDP
Offer/Answer mechanism to negotiate the usage of a single transport (5-tuple)
for sending and receiving media described by multiple SDP media descriptions
("m=" sections).  Such transport is referred to as a BUNDLE transport, and the
media is referred to as bundled media.  The "m=" sections that use the BUNDLE
transport form a BUNDLE group.

To assist endpoints in negotiating the use of bundle this specification defines
a new SDP attribute, 'bundle-only', which can be used to request that specific
media is only used if bundled.  The specification also updates RFC 3264, to
allow assigning a zero port value to a "m=" section without meaning that the
media described by the "m=" section is disabled or rejected.

When RTP-based media is used, there are multiple ways to correlate bundled RTP
packets with the appropriate "m=" section.  This specification defines a new
Real-time Transport Control Protocol (RTCP) source description (SDES) item and
a new RTP header extension that provides an additional way to do this
correlation by using them to carry a value that associates the RTP/RTCP packets
with a specific "m=" section.

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 mechanism has been worked on since 2011, and it has been a WG document
since 2012. Originally, there were different approaches to solving the problem
which resulted in significant disagreements and discussion in the WG about the
best way forward. Ultimately, a compromise proposal agreeable to all parties
was reached (as reflected in the document), and it has been in place for quite
a while with very solid consensus. There has been a number of technical details
to sort out, and the document has also received a lot of editorial feedback.
The current version addresses all known technical issues as well as editorial
comments that can reasonably be addressed (while respecting previous WG
discussions/consensus and also considering sometimes conflicting editorial

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 protocol is an important part of the RTCWeb suite of specifications and
there are existing implementations of earlier versions of the specification.


  Who is the Document Shepherd? Who is the Responsible Area

Flemming Andreasen is the Document Shepherd
Ben Campbell is the Responsile 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.

I have reviewed the current version(s) and several earlier versions of the
document in detail. A number of WG participants have done the same. The
document is ready to proceed.

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

No such concern.

(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.


(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.

Each author has confirmed.

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

No IPR disclosure.

(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?

As described above, there is solid WG concensus behind the document, especially
as it relates to the technical contents. There has been some editorial comments
related to overall readability, however we believe those have been addressed at
this point. The recent version(s) of the document were out for review by the WG
(once again) and did not receive any further feedback.

(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

The document contains a disclaimer for pre-RFC5378 work since it includes
material from RFC 3264.

ID-nits checks produces 2 comments related to references, both of which are
false positives.

(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?

[I-D.ietf-ice-rfc5245bis] was recently submitted for publication.
[I-D.ietf-mmusic-sdp-mux-attributes] is in the RFC Editor's Queue
[I-D.ietf-mmusic-mux-exclusive] is in the RFC Editor's Queue
[I-D.ietf-mmusic-ice-sip-sdp] has completed WGLC

(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.

The document updates RFC 3264, which is indicated on the title page and called
out in the abstract and the 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).

IANA considerations have been reviewed. Registrations are consistent with the
main body of the document and the relevant registry requirements.

(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.