Subject: [MMUSIC] RTSP: Usage of RTP and RTCP Muxing with RTSP media sessions

From: Magnus Westerlund <[email-masked]>
Date: Tue, 11 Sep 2007 16:22:45 +0200

Hi,

draft-ietf-avt-rtp-and-rtcp-mux-07 is currently in the RFC-editor queue.
If we allow for RTP and RTCP muxing with RTSP we can half the port
consumption for a RTSP based streaming server. Or at least avoid RTCP
using additional ports which has been a major complaint from vendors of
high capacity servers. As I can see this can be introduced in the
following ways:

A. Mandate that RTCP MUX shall be supported by RTSP 2.0 servers and
clients supporting RTP transport. A flag indicate may be used to
indicate if RTCP is to be used or not instead of the extra port.

B. Allow RTP and RTCP muxing to be optional to support. Include a flag
to negotiate this usage. Only when both side indicate support is muxing
performed.

I think A is easier and more interoperable in the long run. However it
increase the burden in the transition period from RTSP 1.0 to 2.0.

Please provide feedback on which proposal you favor and why.

Cheers

Magnus Westerlund

IETF Transport Area Director & TSVWG Chair
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Multimedia Technologies, Ericsson Research EAB/TVM/M
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From: Rémi Denis-Courmont <[email-masked]>
Date: Tue, 11 Sep 2007 17:48:19 +0300

Le Tuesday 11 September 2007 17:22:45 Magnus Westerlund, vous avez écrit :
> high capacity servers.

And possibly leverage RTCP-RR as a way to keep the firewall binding open. I 
have not checked if the maximum interval between RTCP-RR is short enough 
though.

> As I can see this can be introduced in the 
> following ways:
>

Actually, I see no problems with B. The server can simply put "a=rtcp-mux" in 
the SDP if it supports it. Then (and only then) the client can specify 
a "port range" of a single port in the SETUP client_port, and the server 
replies accordingly.

A would indeed make clients implementation slightly easier - no need to check 
for server support. However, I would expect implementors to do implement 
various even more complicated tricks as a result of the lack of RTCP mux in 
RTSP/1.0. As such, I would prefer B.

-- 
Rémi Denis-Courmont
http://www.remlab.net/