Re: [AVTCORE] [straw] STRAW WG document review request: draft-ietf-straw-b2bua-rtcp-00

I do not believe that the document even accurately describes a two person video call intermediated by a MANE/SFU. 

> On Feb 4, 2014, at 2:01 AM, "Lorenzo Miniero" <lorenzo@meetecho.com> wrote:
> 
> Colin, Bernard,
> 
> thanks for this feedback, this is exactly what we were waiting for!
> 
> I agree the draft is pretty rough and simple right now. We started this
> way to gather some feedback on whether or not we were heading the right
> direction in the first place, before delving in some more complex use
> cases and scenarios.
> 
> Just as a clarification, it is indeed focused on the simpler two-person
> case right now, but not only audio, actually: the same principles
> described in the draft can be effectively used for a video call between
> two people as well (I'm using them in some implementations as well),
> or at least they should. If you feel this is unclear right now, we can
> try and fix the text to make this clearer.
> 
> We'll definitely address the scenarios you both mentioned in the next
> versions of the draft.
> 
> Thanks,
> Lorenzo
> 
> 
> Il giorno Mon, 3 Feb 2014 08:39:39 -0800
> Bernard Aboba <bernard_aboba@hotmail.com> ha scritto:
> 
>> I agree with Colin that this draft appears focused on a single use
>> case:  a two-person voice call. It does not appear to apply to video
>> use cases, such as those involving a  MANE or Selective Forwarding
>> Unit. For example, the advice in Section 3.2 on processing of
>> feedback messages would not necessarily apply for the case of a
>> MANE/SFU. For example, the MANE/SFU might consume feedback messages
>> sent from a client and not forward them on to the source, instead
>> choosing to address the feedback itself.  For example, in the case
>> where the client reports loss, a MANE may respond by reducing
>> bandwidth going to the client, by for example, dropping one or more
>> extension layers in SVC, or switching to a lower resolution simulcast
>> stream.  
>>> -----Original Message-----
>>> From: Colin Perkins [mailto:csp@csperkins.org] 
>>> Sent: 3. helmikuuta 2014 12:32
>>> To: Christer Holmberg
>>> Cc: avt@ietf.org
>>> Subject: Re: [AVTCORE] STRAW WG document review request:
>>> draft-ietf-straw-b2bua-rtcp-00
>>> 
>>> Christer,
>>> 
>>> From a quick glance, this draft looks okay as far as it goes,
>>> although it seems to assume the B2BUA is processing a call with
>>> only two parties and a single media flow. For example, Section 3.2
>>> has several mentions of "the SSRC" for packets that can contain
>>> multiple SSRCs. With RTCWEB and CLUE both supporting multiparty
>>> calls with multiple media flows, I would suggest that this draft
>>> needs to consider those use cases more fully. 
>>> 
>>> I see no mention of the rewriting the CSRC list, which is straight
>>> forward but necessary if an RTP mixer is in use.
>>> 
>>> The list of RTCP packet types in Section 3.2 is incomplete. The
>>> draft should certainly discuss rewriting RTCP XR packets, and
>>> should probably consider the other RTCP packet types registered
>>> with IANA (even if only to explicitly list them as being for future
>>> specification).
>>> 
>>> There are several cases where that draft says to "properly replace"
>>> a changed sequence number. It might be helpful to be specific what
>>> that means. If the goal is that the B2BUA forwards all packets, but
>>> rewrites the RTP sequence number, then the modifications are
>>> straight forward. If the B2BUA discards, combines, or splits RTP
>>> packets, then the modifications needed get much more complex, and
>>> are not obvious in many cases. Defining the scope clearly, and
>>> explaining what modifications are possible and what need more
>>> complex rules than described, is important here.
>>> 
>>> Some of the discussion in the topologies draft is relevant, but
>>> that draft isn't cited. 
>>> 
>>> There's no mention of media path security (SRTP, etc.), keying, and
>>> how this impacts B2BUAs operating on the media traffic. 
>>> 
>>> Regards,
>>> Colin
>>> 
>>> 
>>> 
>>> On 29 Jan 2014, at 12:27, Christer Holmberg
>>> <christer.holmberg@ericsson.com> wrote:
>>>> Hi,
>>>> 
>>>> In the STRAW WG we are working on the following document:
>>>> 
>>>> http://tools.ietf.org/html/draft-ietf-straw-b2bua-rtcp-00
>>>> 
>>>> The STRAW WG chairs think it would be very useful, and we would
>>>> deeply appreciate, if some people from the AVTCORE community
>>>> would have some time and interest in reviewing and providing
>>>> comments on the document (on the STRAW list). Please let me know
>>>> if you are willing to do such review :) Thanks!
>>>> 
>>>> Regards,
>>>> 
>>>> Christer
>>>> STRAW WG co-chair
>>>> _______________________________________________
>>>> Audio/Video Transport Core Maintenance avt@ietf.org 
>>>> https://www.ietf.org/mailman/listinfo/avt
>>> 
>>> 
>>> 
>>> -- 
>>> Colin Perkins
>>> http://csperkins.org/
>>> 
>>> 
>>> 
>>> _______________________________________________
>>> Audio/Video Transport Core Maintenance
>>> avt@ietf.org
>>> https://www.ietf.org/mailman/listinfo/avt
>>                         