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?
This matches the working group milestone, and is appropriate since the
proposed mechanisms have been evaluated in simulations and are believed
safe, but have not yet been widely tested in real networks. See Section
7 of the draft for discussion.
The intended status is mentioned 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:
The RMCAT working group is developing congestion control schemes for use
with RTP. When multiple such congestion controlled RTP flows traverse the
same network bottleneck, combining their controls can improve the total
on-the-wire behavior in terms of delay, loss and fairness. This document
describes such a method for flows that have the same sender, in a way
that is as flexible and simple as possible while minimizing the amount of
changes needed to existing RTP applications. It specifies how to apply
the method for the NADA congestion control algorithm, and provides
suggestions on how to apply it to other congestion control algorithms.
Working Group Summary
The draft has been under development in the working group for some years.
Much of the time was taken waiting for the candidate congestion control
algorithms to stabilise, mapping the algorithms to the mechanisms given
in this draft, and deciding which congestion control algorithms should be
supported. The coupled congestion control algorithm itself has proved
The draft discusses how to apply coupled congestion control to NADA and
Google Congestion Control. The mapping to NADA is in the main body of the
draft, since NADA is nearing working group last call and believed stable.
The mapping for Google Congestion Control is in an appendix, since Google
Congestion Control is not yet finalised. There is no mapping for SCReAM
at this time, but one could be added later if there was interest in doing
so (nothing in SCReAM should prevent this).
Overall, the working group process has been relatively smooth, although
not rapid. The main issue of contention was the choice of congestion
control algorithm to which the mechanism should be applied - based on
the maturity of the candidate congestion control algorithms, and the
relative importance the authors of the candidates placed on coupled
The algorithm has been implemented in simulations and emulated testbeds.
This is appropriate for an experimental protocol of this type, and meets
the usual community evaluation standards for transport protocol research.
The draft has been reviewed by some authors of each candidate congestion
control algorithm, with Xiaoqing Zhu and Stefan Holmer providing detailed
reviews and advice on integration with the congestion control proposals.
The draft is well written, and the mechanism is clearly specified.
There is no need for MIB Doctor, Media Type, or other expert review,
since the proposed mechanism relies only on common RTP features and
parameters that can be directly measured by the end-point using the
The document shepherd is Colin Perkins.
The responsible AS is Mirja Kuehlewind.
(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 shepherd conducted a detailed review to ensure consistency in
terminology, and to clarify a few points. See https://mailarchive.ietf.org/arch/msg/rmcat/H7E2agZrv-7BDqMrGyoWtZ_ZtbQ/?qid=b6b2bf182bd5a8c93a97c5695a6f0780
and the follow-up discussion. The draft was in good shape after working
group last call, and few issues were noted.
(4) Does the document Shepherd have any concerns about the depth or
breadth of the reviews that have been performed?
No - the reviews and evaluation have been appropriate for an
(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
This is a heavily transport related draft, being focussed entirely
on details of congestion control. Security considerations are adequate,
although they will likely need elaboration for a future standards-track
revision of this work in the light of operational experience. The draft
says little about operational complexity, and the risks of cheating and
poor quality implementations, but this will depend on the experiences
with the protocol, and cannot effectively be done without experimentation
and controlled deployment experience.
(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.
Yes - no disclosures 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 submitted.
(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 document been been widely reviewed. There seems general, but not
overwhelming, consensus from the working group that the mechanism is
useful and applicable to the candidate congestion control algorithms.
(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 such issues.
(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
Some references are to slightly outdated versions of other working group
documents (the changes in the latest version of those documents do not
Pseudo code is not surrounded by <CODE BEGINS> and <CODE ENDS>, but I
do not believe it appropriate to do this.
(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?
There is one reference to an Internet-draft (draft-ietf-rmcat-nada),
but this draft is in working group last call.
(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.
This does not update or change the status of any existing RFCs.
(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 shepherd agrees the draft makes no request to 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.
(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.