Subject: [MMUSIC] A comment re. draft-ietf-mmusic-rfc2326bis-06.txt

From: Ross Finlayson <[email-masked]>
Date: Tue, 23 Nov 2004 13:37:19 -0800

In section 16.4 ("Live Media Presentation Using Multicast") there's the 
following "Editor's Note"):

Is this example really valid? In what situations does it make sense to do a 
setup to a multicast distribution channel, and also issue PLAY requests?

Please remove this "Editor's Note".  As I noted in a message to this 
mailing list back in August:

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Why did this even arise as an issue?  RTSP *is definitely* useful for 
playing multicast sessions.  In particular, the RTSP "DESCRIBE" command is 
an excellent way for a client to get the SDP description for a multicast 
session (even though, in this case, the subsequent "SETUP" and "PLAY" 
commands turn out to be effectively no-ops).

A media player client can play a stream using a "rtsp://" URL, without 
having to know in advance whether the stream is multicast or unicast.  It 
would be silly to require that a media player use one mechanism for playing 
multicast streams, and another for playing unicast streams.

It baffles me that so many people seem to think that RTSP is for unicast 
streams only.  Please don't perpetuate this myth by removing the multicast 
example from the spec.

         Ross (who has implemented and deplayed several multicast streaming 
applications with built-in RTSP servers)

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From: Magnus Westerlund <[email-masked]>
Date: Thu, 25 Nov 2004 16:36:02 +0100

Hi Ross,

See below:

> mailing list back in August:
Yes, I don't see a big problem with removing the editors note. However 
the question was also on a more technical level rather than on the 
principle level.

So have you looked at the actual example and think it is correct?

I am also sorry that I didn't manage to edit the draft to the shape I 
have desired before the meeting. There are a number of open issues not 
edited in, and this editorial note, is clearly one things that needs to 
be concluded.

Cheers

Magnus Westerlund

Multimedia Technologies, Ericsson Research EAB/TVA/A
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