Re: [AVT] Re: Comments on draft-ietf-avt-tfrc-profile-05

[Colin Perkins <csp at csperkins.org>]

Hi,

On 8 Dec 2005, at 22:20, Ladan Gharai wrote:
> > 2. Section 4. RTP data header extension: I think both of the  
> > SHOULDs in this paragraph needs to be MUST. Yes, I am arguing that  
> > AVP has to relaxed wording in regards to header extensions.
> >
> > 3. Section 4. RTP data header extension: Is the first 16 bits  
> > field values shared with the AVP profile or is this a new scope?
>
>     The text on RTP header extensions is verbatim from RFC 3551 -  
> and no this draft does not define new header extensions.

But the question was whether extensions defined for use with RTP/AVP  
can be used with RTP/AVPCC (i.e. do they share a common extension  
type namespace)?

> > 4. Section 4. RTCP report interval: "This profile is restricted to  
> > unicast flows, therefore at all times there is only one active  
> > sender      and one receiver." This formulation is a bit unclear.  
> > As there may only be unicast traffic but that doesn't present  
> > there from being multiple sources (SSRC).
>
>     Other than having a mixer involved, what scenarios exist where  
> unicast does not equate to a single SSRC?

An RTP/AVPCC receiver talking to an RTP translator that acts as a  
conference MCU which switches between sources, rather than mixing  
them. Or when talking to a translator with a multicast group behind  
it, perhaps.

> > 8. This draft is still not declaring the possibility to use AVPF  
> > RTCP feedback messages.
>
>     As it is possible to have multiple senders and receivers with  
> AVPCC, there is a basic conflict between AVPF and AVPCC - as AVPF  
> will suppress feedback packets to prevent implosion, and AVPCC  
> relies on receiving feedback packets for correct congestion  
> control.     Clearly this depends on the scenarios where it is  
> possible to have numerous senders and receivers with AVPCC?

Many of the feedback packets defined in RTP/AVPF are useful in point- 
to-point cases too (e.g. see draft-wenger-avt-avpf-ccm-01.txt).

Colin

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