RTP Control Protocol (RTCP) Extension for a Third-Party Loss Report
draft-ietf-avtcore-feedback-supression-rtp-17

[Ballot comment]
moved from DISCUSS to COMMENT after emails from authors:

(1)

"screwed up" in Section 6.5 is not very technical; please say what is really wrong (loss, corruption, reordering, etc.)


(2)

Section 1 lists a number of *BUGS* in implementations as the motivations for this.  It starts by saying that a use case for this is people not implementing RFC 4585 dithering correctly, then says that another use case is that there are other poor designs causing implosions of FIRs.

It seems silly to write this new RFC adding a new mechanism rather than just applying pressure to fix those implementations; it would be useful to discuss why that isn't the right answer, since receivers have to implement reactions to this new report anyways, they should be fixing their bugs.  I think this is an especially relevant question given the lack of implementation noted in the writeup and Pete's ballot.

[Ballot discuss]
(1)

"screwed up" in Section 6.5 is not very technical; please say what is really wrong (loss, corruption, reordering, etc.)


(2)

Section 1 lists a number of *BUGS* in implementations as the motivations for this.  It starts by saying that a use case for this is people not implementing RFC 4585 dithering correctly, then says that another use case is that there are other poor designs causing implosions of FIRs.

It seems silly to write this new RFC adding a new mechanism rather than just applying pressure to fix those implementations; it would be useful to discuss why that isn't the right answer, since receivers have to implement reactions to this new report anyways, they should be fixing their bugs.  I think this is an especially relevant question given the lack of implementation noted in the writeup and Pete's ballot.

[Ballot comment]

Just checking: there's no way that a 3rd party loss report
could cause a flood of re-transmitted data (that hadn't
actually been lost) to be (re-)sent to a target is there? If
so, that might constitute a new DoS vector. Its not clearly
the case that that can't happen. If it could, then
that'd be another reason to authenticate these messages.

nits/typos:

- s/to pose/pose/
- s/message,which/message, which/
- maybe s/the distribution source will not/if the
  distribution source will not/ in 6.1? (and some
  missing spaces there too)o
- I like "badly screwed up" as a descriptive phrase!

[Ballot comment]
The document writeup says, "There are not yet any reported implementations." Are you really saying that for a protocol that appears to have serious congestion control effects, nobody has written a line of code yet? Has there been any testing of this at all? Are there any planned implementations (perhaps by more than one independent implementer)? If not, perhaps this should be published as Experimental first.

[Ballot comment]
I just have a few questions on this draft:

1. The Protocol Overview section states : "Intermediaries in the network that receive a RTCP TPLR SHOULD NOT send their own additional Third-Party Loss Report messages for the same packet sequence numbers."  Why is this not a MUST?  Is it simply to handle intermediate devices that don't support this function?  If there is another scenario where a device may send a TPLR that overlaps, it would be good to spell that out.

2. There are two places (Sections 4.1 & 4.2) where the length field in the feedback message is set to "2+1*N".  Should I interpret that to mean the value is really just N+2?  Or is there something I am missing?

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:  (RTCP Extension for Third-party Loss Report) to Proposed Standard





The IESG has received a request from the Audio/Video Transport Core

Maintenance WG (avtcore) to consider the following document:

- 'RTCP Extension for Third-party Loss Report'

  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 2012-03-26. 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





  In a large RTP session using the RTCP feedback mechanism defined in

  RFC 4585, a feedback target may experience transient overload if some

  event causes a large number of receivers to send feedback at once.

  This overload is usually avoided by ensuring that feedback reports

  are forwarded to all receivers, allowing them to avoid sending

  duplicate feedback reports.  However, there are cases where it is not

  recommended to forward feedback reports, and this may allow feedback

  implosion.  This memo discusses these cases and defines a new RTCP

  third-party loss report that can be used to inform receivers that the

  feedback target is aware of some loss event, allowing them to

  suppress feedback.  Associated SDP signalling is also defined.









The file can be obtained via

http://datatracker.ietf.org/doc/draft-ietf-avtcore-feedback-supression-rtp/



IESG discussion can be tracked via

http://datatracker.ietf.org/doc/draft-ietf-avtcore-feedback-supression-rtp/ballot/





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

WG Shepherd writeup for "RTCP Extension for Third-party Loss Report"
draft-ietf-avtcore-feedback-supression-rtp-13 to be requested to be
published 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?
       
        The Document Shepherd is Magnus Westerlund. He has completely
        reviewed 09, and has reviewed all the changes of all the
        following versions. He does believe that the document is ready
        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? 
       
        This document has gotten adequate review by WG members, including
        key ones. There has not been seen any need for WG external review.
        The shepherd has no issue with the amount of review
        although more would never hurt.

  (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?
       
        No such issues.

  (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.
       
        No concerns. There are no IPR disclosures against the WG
        document nor, the indiviudal document which the WG one is
        based on.

  (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 WG consensus is strong among a small group of WG participants.
         

  (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.)

No such opinions voiced.

  (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?
       
        Yes, the shepherd has checked the document. There is no formal
        review criteria required on this document.

  (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 references are split. No down-refs appear to exist.
       

  (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 IANA sections appears to be consistent and uses existing
        regestries to add the extension into them.

  (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?
       
        No formal language used.

  (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
        In a large RTP session using the RTCP feedback mechanism defined in RFC
        4585, a feedback target may experience transient overload if some event
        causes a large number of receivers to send feedback at once. This
        overload is usually avoided by ensuring that feedback reports are
        forwarded to all receivers, allowing them to avoid sending duplicate
        feedback reports.  However, there are cases where it is not recommended
        to forward feedback reports, and this may allow feedback implosion. 
        This memo discusses these cases and defines a new RTCP third-party loss
        report that can be used to inform receivers that the feedback target is
        aware of some loss event, allowing them to suppress feedback. 
        Associated SDP signalling is also defined.

    Working Group Summary
        There is strong consensus among an adequate number of WG
        participants on this solution.
       
    Document Quality
    There are not yet any reported implementations. The document
    has had reasonable review.