A Real-time Transport Protocol (RTP) Header Extension for Mixer-to-Client Audio Level Indication
draft-ietf-avtext-mixer-to-client-audio-level-06

[Ballot discuss]
This is a companion to my DISCUSS position on draft-ietf-avtext-client-to-mixer-audio-level. This document takes text from RFC 3389. Should it use the pre5378 boilerplate?

[Ballot discuss]


According to the IETF's TLP you need to put:



/*

  Copyright (c) 2011 IETF Trust and the persons identified
  as authors of the code. All rights reserved.

  Redistribution and use in source and binary forms, with
  or without modification, is permitted pursuant to, and subject
  to the license terms contained in, the Simplified BSD License
  set forth in Section 4.c of the IETF Trust’s Legal Provisions
  Relating to IETF Documents (http://trustee.ietf.org/license-info).

*/

code goes here



in A.1.



[Ballot comment]
Same comments as for client-to-mixer

(1) If vad can expose encrypted vbr, then why don't the security
considerations here say "if encrypting vbr and doing vad then you
MUST use apply commemsurate protection to both"? I don't get the
logic in the current section 6 where it says "if encrypting vbr
and doing vad then you SHOULD use some additional mechanism" -
what's the exceptional case that justifies the SHOULD there and
why would you ever do something appreciably weaker or stronger?

(2) Is the alternative to srtp-encrypted-header-ext to use IPsec
or TLS or what? It'd be better to reference those since if you
don't then I don't get how srtp-encrypted-header-ext isn't a
normative reference? I'd suggest adding a reference to either TLS
or IPsec, whichever is more likely to be used.

[Ballot comment]
1. Lionel Morand made in his OPS-DIR review a number of comments which I suggest to be taken into consideration by the authors or RFC Editor:

* Overall comment: the document defines a new optional RTP header extension to support a new service capability. However, it should be clarified somewhere (e.g. in the protocol description) the condition of service applicability e.g. all the entities involved need to support this extension.

* In section 1, figure 1: even if it is just for illustration, please indicate what would be the meaning of (S) and (M)

* In section 3: I'm not a specialist of RTP and use of mixers. However it might be desirable to extend the section dealing with the possible cascade of mixers. It is not obvious how each mixer will be involved along the path. Especially, it is not clear what is the rational that leads to the conclusion:
"it is likely that in such situations average audio levels would be perceptibly different for the participants located behind the different mixers."

* In section 5, it is said:
  "Conferencing clients that support audio level indicators and have no
  mixing capabilities would not be able to provide content for this
  audio level extension and would hence have to always include the
  direction parameter in the "extmap" attribute with a value of
  "recvonly".  Conference focus entities with mixing capabilities can
  omit the direction or set it to "sendrecv" in SDP offers.  Such
  entities would need to set it to "sendonly" in SDP answers to offers
  with a "recvonly" parameter and to "sendrecv" when answering other
  "sendrecv" offers."

Question: Is the setting of the direction parameter purely informative (sorry for my ignorance)? If not i.e. there are associated requirements, the above text is not appropriate (e.g. "would have to always", "would need") and "MUST" should be used instead.

* Figure 4 and 5: The description of each example should be put above the figures. Even if obvious, please indicate for clarification "SDP Offer:" and "SDP Answer:" on top of the lists of SDP parameter.

* Figure 4:
  "A client-initiated example SDP offer/answer exchange negotiating an
  audio stream with one-way flow of of audio level information."

s/one-way flow of of audio/one-way flow of audio

2. Please expand CSRC at first occurence

3. Please replace the conditional language in the first paragraph of the IANA considerations section.

IANA understands that, upon approval of this document, there is a single
IANA Action which must be completed.

In the RTP Compact Header Extensions sub-registry of the Real-Time
Transport Protocol (RTP) Parameters registry, located at:

http://www.iana.org/assignments/rtp-parameters

a new registration will be made as follows:

Extension URI: urn:ietf:params:rtp-hdrext:csrc-audio-level
Description: Mixer-to-client audio level indicators
Contact: emcho@jitsi.org
Reference: [ RFC-to-be ]

IANA understands that this is the only actions required to be completed
upon approval of this document.

State changed to In Last Call from Last Call Requested.

The following Last Call Announcement was sent out:

From: The IESG
To: IETF-Announce
CC:
Reply-To: ietf@ietf.org
Subject: Last Call:  (A Real-Time Transport Protocol (RTP) Header Extension for Mixer-to- Client Audio Level Indication) to Proposed Standard


The IESG has received a request from the Audio/Video Transport Extensions
WG (avtext) to consider the following document:
- 'A Real-Time Transport Protocol (RTP) Header Extension for Mixer-to-
  Client Audio Level Indication'
  as a Proposed
Standard

The IESG plans to make a decision in the next few weeks, and solicits
final comments on this action. Please send substantive comments to the
ietf@ietf.org mailing lists by 2011-10-04. Exceptionally, comments may be
sent to iesg@ietf.org instead. In either case, please retain the
beginning of the Subject line to allow automated sorting.

Abstract


  This document describes a mechanism for RTP-level mixers in audio
  conferences to deliver information about the audio level of
  individual participants.  Such audio level indicators are transported
  in the same RTP packets as the audio data they pertain to.




The file can be obtained via
http://datatracker.ietf.org/doc/draft-ietf-avtext-mixer-to-client-audio-level/

IESG discussion can be tracked via
http://datatracker.ietf.org/doc/draft-ietf-avtext-mixer-to-client-audio-level/


No IPR declarations have been submitted directly on this I-D.

Proto writeup for "A Real-Time Transport Protocol (RTP) Header
Extension for Mixer-to-Client Audio Level Indication", draft-ietf-
avtext-mixer-to-client-audio-level-05 as proposed standard

  (1.a) Who is the Document Shepherd for this document? Has the
        Document Shepherd personally reviewed this version of the
        document and, in particular, does he or she believe this
        version is ready for forwarding to the IESG for publication?

Keith Drage is the document shepherd. The document has had extensive
review and is ready for forwarding to the IESG for publication.

  (1.b) Has the document had adequate review both from key WG members
        and from key non-WG members? Does the Document Shepherd have
        any concerns about the depth or breadth of the reviews that
        have been performed? 

The history of the document is as follows:

- draft-ivov-avt-slic-00 was submitted 15th June 2009 and
expired 17th December 2009.
- draft-ivov-avt-slic-01 was submitted 19th October 2009 and
expired 22nd April 2010.
- draft-ivov-avt-slic-02 was submitted 26th October 2009 and
expired 29th April 2010.
- draft-ivov-avt-slic-03 was submitted 11th July 2010 and
expired 12th January 2011.
- draft-ivov-avt-slic-04 was submitted 16th January 2011 and
expired 20th July 2011.
- draft-ietf-avtext-mixer-to-client-audio-level-00 was
submitted 18th February 2011 and expires 22nd August 2011.
- draft-ietf-avtext-mixer-to-client-audio-level-01 was
submitted 14th March 2011 and expires 15th September 2011.
- draft-ietf-avtext-mixer-to-client-audio-level-02 was
submitted 9th May 2011 and expires 10th November 2011.
- draft-ietf-avtext-mixer-to-client-audio-level-03 was
submitted 5th July 2011 and expires 6th January 2012.
- draft-ietf-avtext-mixer-to-client-audio-level-04 was
submitted 27th August 2011 and expires 28th February 2012.
- draft-ietf-avtext-mixer-to-client-audio-level-05 was
submitted 5th September 2011 and expires 8th March 2012.

The document was originally targetted at the AVT working group, and
with the split of the charter of AVT into 4 new groups, fell within
the scope of the AVTEXT working group.

The document was adopted by the AVTEXT working group on 14th February
2011. WGLC was initiated 6th July 2011 to complete 20th July 2011 on -
03 version as proposed standard. Working group last call comments
were received from Keith Drage, Magnus Westerlund, Kevin Fleming.
Indications were received from the following that they had read the
document and that it was ready to go: Stephan Wenger, John Elwell,
Peter Musgrave. An indication was also taken in the AVTEXT face to
face meeting and 10 - 15 people identified they had read and were OK
with the WGLC version.

There are no concerns about the depth or breadth of review.

  (1.c) Does the Document Shepherd have concerns that the document
        needs more review from a particular or broader perspective,
        e.g., security, operational complexity, someone familiar with
        AAA, internationalization or XML?

The document contains an SDP extension that has been reviewed by
experts from the MMUSIC working group (specifically Miguel Garcia).
Some comments were made which have been addressed to the satisfaction
of the reviewer.

  (1.d) Does the Document Shepherd have any specific concerns or
        issues 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. Has an IPR disclosure related to this document
        been filed? If so, please include a reference to the
        disclosure and summarize the WG discussion and conclusion on
        this issue.

There are no specific concerns or issues with this document.

No IPR disclosures have been made against this document or its
predecessors.

  (1.e) 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 has WG concensus and appears to be well supported.

  (1.f) 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
        entered into the ID Tracker.)

There has been no issues for appeal or otherwise discontent
identified during the discussion.

  (1.g) Has the Document Shepherd personally verified that the
        document satisfies all ID nits? (See the Internet-Drafts
Checklist
        and http://tools.ietf.org/tools/idnits/). Boilerplate checks
are
        not enough; this check needs to be thorough. Has the document
        met all formal review criteria it needs to, such as the MIB
        Doctor, media type and URI type reviews?

Apart from the MMUSIC review already mentioned, no other external
reviews have been identified as necessary for this document.

The document was checked with idnits 2.12.12 and no issues were
identified.

  (1.h) Has the document split its references into normative and
        informative? 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
        strategy for their completion? Are there normative references
        that are downward references, as described in [RFC3967]? If
        so, list these downward references to support the Area
        Director in the Last Call procedure for them [RFC3967].

The document has split its references into normative and informative
references, and these references have been checked to be in the
appropriate group.

There is an informative reference to an unpublished document, draft-
lennox-avtcore-srtp-encrypted-header-ext, and the final publication
of this document should be held until this document receives an RFC
number. Similarly draft-ietf-avtext-client-to-mixer-audio-level
should also receive an RFC number before this document is published.
Publication should not wait for other unpublished documents.

  (1.i) Has the Document Shepherd verified that the document IANA
        consideration section exists and is consistent with the body
        of the document? If the document specifies protocol
        extensions, are reservations requested in appropriate IANA
        registries? Are the IANA registries clearly identified? If
        the document creates a new registry, does it define the
        proposed initial contents of the registry and an allocation
        procedure for future registrations? Does it suggest a
        reasonable name for the new registry? See [RFC5226]. If the
        document describes an Expert Review process has Shepherd
        conferred with the Responsible Area Director so that the IESG
        can appoint the needed Expert during the IESG Evaluation?

The document makes one entry to the RTP Compact Header Extensions
subregistry of the Real-Time Transport Protocol (RTP) Parameters
registry and this is defined in the document in an IANA
considerations section. The registration requirement for this
registry is Expert Review which may be considered to have already
occurred, AVTEXT being the appropriate expert working group.

  (1.j) Has the Document Shepherd verified that sections of the
        document that are written in a formal language, such as XML
        code, BNF rules, MIB definitions, etc., validate correctly in
        an automated checker?

The document contains no formal language to validate.

  (1.k) 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.
    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
        rough?
    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?

This document describes a mechanism for RTP-level mixers in audio
conferences to deliver information about the audio level of
individual participants.  Such audio level indicators are transported
in the same RTP packets as the audio data they pertain to.

The document is a product of the AVTEXT working group.

Jitsu has a working and deployed implementation of this internet-
draft.