Subject: RE: [Sipping] Conference speaker control

From: "Even, Roni" <[email-masked]>
Date: Sat, 4 Dec 2004 16:04:20 +0200

Magnus,
The whole discussion is about the SIP conference package that suggests
that a SIP user will know the source of the stream based on SSRC. So if
there are media sessions that are not RTP is a SIP call then SSRC does
not work. 
Roni

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On
Behalf Of Magnus Westerlund
Sent: Friday, December 03, 2004 11:11 AM
To: Even, Roni
Cc: sipping; David R Oran
Subject: Re: [Sipping] Conference speaker control

Even, Roni wrote:
> Hi,
> This is from the comedia draft, is it RTP, it does not say so.
> 
>            m=image 54111 TCP t38
>            c=IN IP4 192.0.2.2
>            a=setup:passive
>            a=connection:new
> 
> Roni

No, that is clearly T38 over TCP which has a mode that is not RTP, 
however if you look in the RTP over TCP draft:
http://www.ietf.org/internet-drafts/draft-ietf-avt-rtp-framing-contrans-
03.txt

You can find the following SDP:
v=0
o=first 2520644554 2838152170 IN IP4 first.example.net
s=Example
t=0 0
c=IN IP4 192.0.2.105
m=audio 9 TCP/RTP/AVP 11
a=setup:active
a=connid:1

It is also this draft that register the RTP over TCP SDP protocol 
identifier.

Cheers

Magnus Westerlund

Multimedia Technologies, Ericsson Research EAB/TVA/A
----------------------------------------------------------------------
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---

From: David R Oran <[email-masked]>
Date: Sat, 4 Dec 2004 17:15:16 -0500

> there are media sessions that are not RTP is a SIP call then SSRC does
While this is strictly true, that's not the point. The point is whether  
the conferencing work ought to rely on a "correlator" in or associated  
with the media stream, and have arrivals on the media stream trigger  
any UI behavior, in order to identify the  
source(s)/speakers/arm-wavers/typers/gas-emitters.

I believe it should. In the case of RTP, this is the SSRC or the CNAME  
or both.

If the conferencing system wishes to accommodate a media session  
without this identification capability there has to be some way to do  
the correlation. I'm suggesting that emulating the media session by  
actually always having one to the UA is a good way to do this rather  
than sending speaker identification messages in realtime over the  
conferencing control protocols.

What do others think? This is important enough that other folks ought  
to weigh in here.

Dave.

> Multimedia Technologies, Ericsson Research EAB/TVA/A
David R. Oran
Cisco Fellow
Cisco Systems
7 Ladyslipper Lane
Acton, MA 01720 USA
Tel: +1 978 264 2048
Email: [email-masked]