As required by RFC 4858, this is the current template for the Document
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?
A Proposed Standard RFC is being requested. The document describes normative multiplexing behavior for media-level SDP attributes when multiplexing media for those "m=" lines on the same media transport. The title page indicates "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:
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
For scenarios where SDP is used to negotiate the usage of single 5-
tuple for sending and receiving media associated with multiple media
descriptions, it is required to understand the semantic implications
of the SDP attributes associated with the RTP Media Streams
multiplexed over a single underlying transport layer flow.
The purpose of this specification is to provide a framework for
analyzing the multiplexing characteristics of SDP attributes. This
specification also categorizes the existing SDP attributes based on
the framework described herein.
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
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 document was extensively reviewed and discussed by a large number of MMUSIC members (listed in Acknowledgements section).
Who is the Document Shepherd? Who is the Responsible Area
The Document Shepherd is Bo Burman.
The Responsible AD 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 document shepherd read the submitted version of the document fully, with specific focus on IANA aspects, and found no issues.
(4) Does the document Shepherd have any concerns about the depth or
breadth of the reviews that have been performed?
There are no concerns. The document got good review from many MMUSIC members and all comments were addressed.
(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
(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
(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 that he does not know of any IPR disclosures that would be required.
(8) Has an IPR disclosure been filed that references this document?
If so, summarize any WG discussion and conclusion regarding the IPR
No IPR disclosures have 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?
A large number of key people have commented on the draft in MMUSIC, and all comments are addressed in the current draft.
(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 https://www.ietf.org/tools/idnits/ and the Internet-Drafts
Checklist). Boilerplate checks are not enough; this check needs to be
A few nits are identified, but all are intentional and should be OK:
* The supposedly non-RFC2606-compliant FQDNs are not FQDNs but references to existing 3GPP-defined SDP attributes.
* The use of "NOT RECOMMENDED" is intentionally not in the RFC 2119 boilerplate, because it is never used in regular RFC 2119 sense but instead a defined multiplex category defined in this document.
* Explicit reference to the obsoleted RFC 4091 instead of the replacing RFC 5245 is motivated by explicitly stating that the ANAT semantics from RFC4091 is obsoleted.
(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?
This document normatively references ietf-mmusic-sdp-bundle-negotiation, which has a normative reference back to this document. The ietf-mmusic-sdp-bundle-negotiation document has no other normative references to Internet Drafts, and has concluded 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.
(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 document shepherd made an extensive review of the IANA section and its relation to and consistency with the document body. The IANA registry reference is correct, and the requirements for the new first-come first-serve "Multiplexing Categories" sub-registry is well described. The addition of the new "Mux Category" column to several existing IANA SDP attribute sub-registries is also well described.
(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.