Subject: [MMUSIC] SDPCapNeg-06: Lack of bandwidth capabilities

From: Magnus Westerlund <[email-masked]>
Date: Thu, 19 Jul 2007 19:13:27 +0200

The current proposal total failes to discuss the bandwidth parameter in 
SDP. This is a serious shortcomming and will result in real issues for 
the profiles. Different profiles and usages will have different 
bandwidth parameters. Although media bandwidth may different for 
different potential configurations I think the major issue exist for the 
RR and RS attribute which really makes sense to configure differently 
for different profiles. For example AVPF with some feedback may require 
much more RTCP bandwidth than AVP. And in case one uses the TFRC 
addition one may have need for yet another configuration. Thus there is 
need to be able to connect different bandwidth configurations with 
specific potential configurations.

Cheers

Magnus Westerlund

IETF Transport Area Director & TSVWG Chair
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From: "Stach, Thomas" <[email-masked]>
Date: Fri, 20 Jul 2007 12:24:44 +0200

Magnus,

I agree that this is neither covered in the core spec nor in the media
capability extension.
Could that be left for an extension (either its own or media
capabilities) in order to keep the core spec simpler?

Regards
Thomas 

> -----Original Message-----
> From: Magnus Westerlund [mailto:[email-masked]] 
> Sent: Thursday, July 19, 2007 7:13 PM
> To: mmusic (E-mail)
> Subject: [MMUSIC] SDPCapNeg-06: Lack of bandwidth capabilities
>

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From: "Even, Roni" <[email-masked]>
Date: Fri, 20 Jul 2007 20:16:55 +0300

Thomas,
I think we may cover it in the media capabilities.
Still I think that we may decide that we can use RTCP CCM for flow
control to lower BW based on selected mode.
Roni

> From: Stach, Thomas [mailto:[email-masked]]
> Sent: Friday, July 20, 2007 1:25 PM
> To: Magnus Westerlund; mmusic (E-mail)
> Subject: RE: [MMUSIC] SDPCapNeg-06: Lack of bandwidth capabilities
> 
> Magnus,
>

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From: Flemming Andreasen <[email-masked]>
Date: Mon, 23 Jul 2007 11:49:27 -0400

Magnus Westerlund wrote:
> The current proposal total failes to discuss the bandwidth parameter 
> in SDP. This is a serious shortcomming and will result in real issues 
> for the profiles. Different profiles and usages will have different 
> different potential configurations I think the major issue exist for 
> the RR and RS attribute which really makes sense to configure 
> differently for different profiles. For example AVPF with some 
> feedback may require much more RTCP bandwidth than AVP. And in case 
> one uses the TFRC addition one may have need for yet another 
> configuration. Thus there is need to be able to connect different 
> bandwidth configurations with specific potential configurations.
>
We don't have a requirement for this currently, however your point is 
well taken. I think we have two options here:
1) Add a section noting the interaction issue.
2) Add a new requirement to address this and incorporate it (relatively 
straightforward: we define a "bandwitdh" capability and allow it to be 
referenced as part of the potential and actual configuration - the 
original "bandwidth" parameter from the actual configuration would be 
replaced automatically).

I'm open either way and look to the WG for further guidance on this.

-- Flemming

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From: Magnus Westerlund <[email-masked]>
Date: Mon, 23 Jul 2007 21:04:39 +0200

> capabilities) in order to keep the core spec simpler?

In my opinion, NO!

The reason is that different transport capabilities do need different 
bandwidth modifiers to make the work correctly. Thus, not providing this 
in the core will have serious effect for usage of some transport options 
for RTP.

Cheers

Magnus Westerlund

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From: Magnus Westerlund <[email-masked]>
Date: Mon, 23 Jul 2007 21:09:55 +0200

> control to lower BW based on selected mode.

Well, that is not really what CCM is intended to be used for. It also 
doesn't allow the answerer to determine if a potential configuration has 
a reasonable bandwidth configuration to be accepted.

I also think that we should consider the RTCP bandwidth configuration 
that is very much tied into the transport used. Difference between AVP 
and AVPF.

Cheers

Magnus Westerlund