[EMAIL PROTECTED] wrote:
If I understand the description below correctly, sequential ring service
is sequentially forkinging to different destinations. Dialog with
B(sequential ring server) is different from dialog established with C
(with a different To-tag).
Hence 200 OK from C can contain a different SDP.
and then Nathan Ning answered:
Ramakrishna,
You are right.
Which from the view of A side, there is only one dialog.
Since the service is on B side, and the call request is forward
by B to C, and A don't know that the final 200 OK is from C.
It is a interesting thing. :)
I agree with Ramakrishna. Responding to Nathan, no this doesn't appear
as one dialog to A. The 183 response from B will have one to-tag, and
the 200 response from C will have a different to-tag. This makes them
different dialogs from A's perspective. When A receives the final
response from C it abandons the early dialog with B. (It assumes it was
cancelled by the forking proxy.)
It is *wrong* to send different SDP in an unreliable provisional
response and then in a reliable final response *on the same dialog*.
The situation changes if you introduce reliable provisional responses
and UPDATE. So that is another way for you to achieve what you seem to
be looking for:
B could send a *reliable* 183 with an answer. Later, when C is ready, a
new offer can be sent in an UPDATE. These would be in a single dialog.
That probably only works if B acts as a B2BUA between A and C.
Paul
-----Original Message-----
From: Nathan Ning [mailto:[EMAIL PROTECTED]
Sent: Tuesday, October 11, 2005 12:26 PM
To: Ramakrishna Adukuri (WT01 - Voice & Next Generation Networks)
Cc: [EMAIL PROTECTED]; [email protected]
Subject: Re: [Sip-implementors] 183 Early Media with SDP
While there is real case that the UAC receives different SDP in 1XX and
200 OK, and should not ignore the SDP in 200 OK. Following is the case
I met.
A, B, C are sip UE.
B owns sequential ring service(to C).
A calls to B, B rings but not to answer B, timer expires, and C rings, C
off hook.
A talking to C.
In the above case, when Invite request reach to B, B may response with
183(SDP) firstly to connect A to a media server to hear announcement.
While the first call attempt will be cancelled, and when C off hook, A
will got a 200 OK (SDP) related to C.
thanks,
Nathan
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