Re: [Fecframe] request for pub draft-ietf-rtp-raptor-04

["Luby, Michael" <[e-mail]>]

Hi Vincent,
Some comments inline.
Best, Mike


On 3/18/11 7:18 AM, "Vincent Roca" <[e-mail]> wrote:

> Greg, Mike, everybody,
> 
> We had a discussion last month on the topic:
>          "Managing losses between the sending application
>           and the FECFRAME instance"
> as part of the framework I-D (see the bottom of page 41 for
> the agreed text).
> 
> The RTP Raptor I-D is of course concerned by this discussion
> and unfortunately this -04 version is from November 2010,
> before the discussion.
> 
> Unless I missed some key sentence, I have the feeling that this
> I-D implicitly assumes there CANNOT be any RTP packet loss
> before reaching the Fecframe encoder, i.e. the RTP SN are always
> in sequence.
*** Yes, makes sense.
> 
> (NB: the only text I've found that discusses RTP SN is in
> section 3 and does not mention this requirement at all)
> 
> It's a critical requirement that MUST be clearly stated. If there is
> any risk this requirement does not hold, the I-D MUST define an
> appropriate behavior. So it's worth a quick fix (it's fairly easy) IMHO.
> Note that it might also be an attack (in specific deployment
> scenarios, not all of them of course), so it's also worth saying a
> few words in section 12 as well (BTW, we should do the same in
> the FEC Framework I-D, I didn't realize that before, sorry).

*** There seems to be a couple of ways to solve this.  One, as you suggest,
is to mandate that the solution must have all source packets arrive at the
FEC encoder.  Another way is to have logic at the FEC encoder that detects
if there are missing packets (easy to do in this case because of the RTP
sequence numbers), and if so, for FEC encoding purposes (not transmission
purposes), creates a dummy packet of all zeroes for each missing sequence
number (or whatever the receiver is going to interpret as a valid packet but
with no real audio/video info inside), and encode the source block including
the dummy packet(s).  Probably best to point out the problem and then
mention some possible ways to solve it.

*** It should be noted that in any system where not all the source packets
containing video/audio data get to the FEC encoder is pretty badly designed,
as no matter how you overcome it, you are still going to be missing
video/audio at all the clients that receive the stream.  At least if you
have RTP sequence numbers in the source packets you will know this at the
FEC encoder (may not be true of other solutions, i.e., it may even be hard
to detect that not all the video/audio source packets get to the FEC
encoder, and this probably should be pointed out for other solutions).
  
> 
> Cheers,
> 
>    Vincent
> 
> On 11/03/11 13:13, Greg Shepherd wrote:
>> *,
>> 
>> The document draft-ietf-fecframe-rtp-raptor-04 is now ready for
>> publication. Please see the Document Shepherd Write-up below.
>> 
>> Thanks,
>> Greg
>> 
>> ---
>> 
>> Document Shepherd Write-up for draft-ietf-rtp-raptor-04 as per RFC
>> 4858, template dated September 17, 2008
>> 
>> (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?
>> 
>> I, Greg Shepherd as the document shepherd have personally reviewed
>> this document and believe it to be ready for forwarding to the IESG.
>> 
>> (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 document has had adequate review both from within and from outside
>> the FECFrame working group.
>> 
>> (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?
>> 
>> There are no concerns regarding the need for additional expanded review.
>> 
>> (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 with this document.
>> 
>> (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?
>> 
>> There is solid WG consensus for this document.
>> 
>> (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 is no discontent.
>> 
>> (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?
>> 
>> Only two miscellaneous warnings  and one outdated reference which can
>> be addressed with editor's notes:
>> 
>>    == The copyright year in the IETF Trust and authors Copyright Line does
>> not
>>       match the current year
>> 
>>    -- The document date (November 25, 2010) is 46 days in the past.  Is this
>>       intentional?
>> 
>>    == Outdated reference: A later version (-04) exists of
>>       draft-ietf-fecframe-raptor-02
>> 
>> (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].
>> 
>> Normative and informative references are split with two reference to
>> drafts that are currently in the editor's queue or will be soon.
>> 
>> (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?
>> 
>> Section 12 describes the IANA considerations, which refers to Section
>> 5 for a comprehensive registration description. The document itself is
>> primarily a document of media registrations/definitions.
>> 
>> (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 xml code validates correctly
>> 
>> (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
>> This document specifies an RTP payload format for Forward Error
>> Correction /  (FEC) repair data produced by the Raptor FEC schemes.
>> Raptor FEC schemes are specified for use with the IETF FEC Framework
>> which supports transport of repair data over both UDP and RTP. This
>> document specifies the payload format which is required for the use of
>> RTP to carry Raptor repair flows.
>> 
>> Working Group Summary
>> There were no seriously contentious issues during the WG process.
>> 
>> Document Quality
>> The Working Group feedback covered both the quality of the document
>> itself as well as the technical issues with the content of the
>> document.
>> 
>> Personal
>> Document Shepherd - Greg Shepherd
>> Responsible Area Director - David Harrington<[e-mail]>
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