Subject: [MMUSIC] RTSP: ETag

From: Magnus Westerlund <[email-masked]>
Date: Fri, 03 Mar 2006 13:43:13 +0100

Hi,

I have found a issue with ETag. As currently defined in version 11 draft 
there is not clear how one uses ETag and successfully provide the tags 
in all cases. The issue boils down to how ETag should work in RTSP. I 
currently see two cases.

A. One Tag for everything. One uses the same ETag for the session 
presentation and all the media streams.

B. We use individual tags for each component of a presentation and bind 
them together in the session description. Thus the session description 
itself will have one tag, then each media stream will have one tag. The 
ETags are introduced in the session description for each media stream if 
used.

As I see it A will be simpler to implement. The benefit of B is that it 
avoids having a cache to discard streams unnecessary. If one change a 
single aspect of a presentation A will force one to update all parts as 
the caching entity can't determine what has changed, which B would.

Unless someone speaks up I will change the ETag to work as A.

Cheers

Magnus Westerlund

Multimedia Technologies, Ericsson Research EAB/TVA/A
----------------------------------------------------------------------
Ericsson AB                | Phone +46 8 4048287
Torshamsgatan 23           | Fax   +46 8 7575550
S-164 80 Stockholm, Sweden | mailto: [email-masked]

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