Re: [AVT] Non-compound RTCP

["Ingemar Johansson S" <ingemar.s.johansson at ericsson.com>]

Hi

I guess there is a preference to allow for mutiple messages and I guess
I can live with this, however with some disclaimer that small feedback
packets are to be preferred atleast in the "wireless optimized radio
bearer world" that I come from. Guess that this preference does not
apply to all usage scenarios and access types. 

One problem is maybe that as applications should preferrably not care
about the access type, problems may arise if large feedback packets from
eg. a UA connected to a wireline access enter a system that is optimized
for transmission of small packets (e.g 3GPP HSPA optimized for VoIP). In
the latter wireless system there is a potenial risk that the feedback is
lost due to eg lower layer fragmentation and the following increased
sensitivity to poor channel conditions.
The scenario above is one of the main reasons to why this non-compound
RTCP stuff was brought up.  

Comments welcome

Regards
/Ingemar
 

> -----Original Message-----
> From: Randell Jesup [mailto:rjesup at wgate.com] 
> Sent: den 11 mars 2008 23:41
> To: Ingemar Johansson S
> Cc: David R Oran; avt at ietf.org
> Subject: Re: [AVT] Non-compound RTCP
> 
> "Ingemar Johansson S" <ingemar.s.johansson at ericsson.com> writes:
> >> > Personally I am more in favor or version 2) above as it 
> is more in 
> >> > line with how the feedback messages can be stacked in 
> RFC4585 and 
> >> > in the codec control messages draft... with the disclaimer that 
> >> > single messages are preferred.
> 
> I prefer 2 also, though I can certainly live with either.
> 
> >> The words "single messages are to be preferred" could mean 
> that you 
> >> prefer to have only 1 RTCP packet per UDP packet, or that 
> you prefer 
> >> to have as many RTCP packets per UDP packet as you can given space 
> >> and timing constraints. I certainly hope you mean the latter.
> >
> >Sorry for the very weak formulation, actually I my preference is for 
> >single messages in each RTCP with the purpose to keep the 
> total size of 
> >the non-compound RTCP as small as possible. The reasons behind this 
> >preference is to be found in section 3 in
> 
> >http://tools.ietf.org/html/draft-ietf-avt-rtcp-non-compound-03
> 
> >That said, I am not a very religious guy, I believe that it may be 
> >possible to allow for multiple messages in a non-compound 
> RTCP but then 
> >one must keep in mind that the whole idea with non-compound RTCP 
> >diminishes as the size ratio between compound and non-componud RTCP 
> >decreases with the number of feedback messages.
> 
> Right. The idea behind non-compound is to reduce the size of 
> the messages by not sending items you don't *need* to send.  
> If you have multiple things to send, then (maybe) it makes 
> more sense to send one packet with multiple things than N 
> packets with one thing.  You still don't want to send stuff 
> that there's no purpose for, and SR/RR/SDES don't need to be 
> sent more often than in RFC 3550/etc.
> 
> --
> Randell Jesup, Worldgate (developers of the Ojo videophone), 
> ex-Amiga OS team rjesup at wgate.com "The fetters imposed on 
> liberty at home have ever been forged out of the weapons 
> provided for defence against real, pretended, or imaginary 
> dangers from abroad."
> 		- James Madison, 4th US president (1751-1836)
> 
> 
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