Subject: SDP question: specification of media properties

From: Liming Wei <[email-masked]>
Date: Mon, 14 Jul 1997 16:04:45 -0700

Mark,

I have some questions on how flexible SDP can be in specifying the media
properties. Two scenarios are:
 (1) A session uses multi-layered encodings and each "layer" is sent
     on a different group address;
 (2) a "large tele-conference" application, needing to specify 5 out of
     1000 participants as the "primary" sites needing extra
     reliability (than the rest).

The questions are:

Is it possible to convey these in the current SDP ? or the next
revision of SDP ?

Is it possible to convey these with your SDR tool ?

-Liming Wei

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From: Mark Handley <[email-masked]>
Date: Mon, 14 Jul 1997 19:09:52 -0400

>     on a different group address;

If you don't mind consecutive addresses, SDP has no problem.  If you
want to use admin scoped addresses there is currently no convention
for how to use SDP.

>     reliability (than the rest).

I'm not convinced you want to do this in SDP - it sounds far more like
a conference control mechanism to me.  BUt if you really wanted to do
it in SDP, you could do so using attributes.

>Is it possible to convey these with your SDR tool ?

Sdr can always be extended to handle new attributes, but currently it
doesn't handle multiple addresses per medium.  This is a bug.

Mark

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From: Liming Wei <[email-masked]>
Date: Mon, 14 Jul 1997 16:27:09 -0700 (PDT)

> it in SDP, you could do so using attributes.

There is a long story (ommitted here). And yes I think the attribute
field is a good candidate.

> doesn't handle multiple addresses per medium.  This is a bug.

Right. Is there any intention/plan to let users enter multiple addresses
in SDR for each media type ?

 Thanks.
-Liming