[Telepathy] Media API redesign for SIP SOA and ICE

Olivier Crête olivier.crete at collabora.co.uk
Tue Jun 12 13:09:49 PDT 2007


I'm sorry I didn't take the time to read earlier, but I was kind of busy
with other things.

I kind of like the whole idea of a transactional object (I've always
wanted to implement some kind of transactional system), but I'm afraid
that in the current timeframe, it would require too many changes to
farsight's API to be implementable, although it is probably a good idea
to think about it for Farsight 2.

Anyways, I have a few questions.

On Mon, 2007-04-06 at 00:06 +0300, mikhail.zabaluev at nokia.com wrote: 
> I've been thinking over the mapping of the StreamHandler and related
> APIs to semantics required for SDP Offer-Answer and ICE.
> There are a few problems with the current interfaces:
> - There is no good way to change the effective set of codecs and
> effective transport addresses all at once for a stream, which is
> required by SOA specification on session updates.
> - Similarly, there is no good way to roll back the stream state if an
> update offer gets rejected by local or remote party.

Do you know if there is any requirement for the stream to keep its RTP
properties when the candidates is changes? (ie, can't we just create a
completely new stream?).

> - No clear way to implement forking with several provisional responses
> arriving from different endpoints, each potentially carrying an SDP
> answer. Until a 200 response arrives, the implementation cannot assume
> which session will finally be accepted, but it must at least respond
> to incoming ICE checks for every session. 

My reading of the SDP Offer-Answer stuff was that there could be a
single negotiation going on at one time. As for the SIP provisional
responses, can't you just create multiple streams with remote candidates
but no remote codecs and set_sending to false (so the streams don't try
to send anything). And maybe something to prevent them from actually
receiving any data.

Olivier Crête
olivier.crete at collabora.co.uk
Collabora Ltd
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