Subject: RE: [Sip] Playing media message on unanswered call

From: "Rayees Khan" <[email-masked]>
Date: Thu, 18 Oct 2007 18:26:59 +0100

The AS can play media straightway only if it is in the media path and it
supports the negotiated codec. 
In other case, AS needs to change the media path/capabilities. One of
the ways to do that is use UPDATE method, though this would work only if
the UA supports UPDATE.

regards

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]

Sent: Thursday, October 18, 2007 3:42 PM
To: [email-masked]
Subject: [Sip] Playing media message on unanswered call

Hello all,

I am thinking about one problem, consider following message flow:

1. UE A sends SIP INVITE message with SDP offer to EU B 2. On
originating call leg there is application server announced about the
call.
3. 180 Ringing message with SDP answer is sent from UE B to UE A (AS is
announced that the call is in progress) 4. Time frame allocated to
establish the call passed at AS and the message needs to be played ...

Can now the AS make use of negotiated media paths and play some "called
party not available" message without sending 200 OK message first?

My assumption here is that media paths are negoiated (UE A claims
sendrecv audio channel so it must be prepare to receive media) so AS
"can" send this message.

Consider also little complication, AS is not able to play media in a
codec claimed in the answer. Can AS send another 180 ringing message
where the appropriate codec will be issued?

I will appreciate any clarification on this issues.

br, Martin

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