Subject: [Sipping] Forking and reliable provisionnal responses

From: "CHEVRIER SONIA" <[email-masked]>
Date: Tue, 13 Mar 2007 11:11:37 +0100

Hello,

In case an application works as a B2BUA and sends an INVITE with SDP to
a user B that is forked.
The first reliable provisional response from B that contains SDP answer
is sent by the application towards A that acknowledges it by a PRACK
request.
When another reliable provisional response that contains SDP answer is
received (from a user C because of forking), what must be the behaviour
of the application ?
Does it have to sent this reliable provisional response with C's SDP to
user A and wait for PRACK request ?
Or does it have not to sent this reliable provisional response to user A
but only acknowledge the reliable provisional response from C by a PRACK
request ?

Best regards,
Sonia Chevrier
_______________________________________________
Sipping mailing list  https://www1.ietf.org/mailman/listinfo/sipping
This list is for NEW development of the application of SIP
Use [email-masked] for questions on current sip
Use [email-masked] for new developments of core SIP

---

From: Paul Kyzivat <[email-masked]>
Date: Tue, 13 Mar 2007 08:56:03 -0400

> received (from a user C because of forking), what must be the behaviour 

This depends on the intentions of the B2BUA.

It must properly handle this as a UA for A, B, and C. This means that it 
must not send both answers to A using the same to-tag. It could use a 
single early dialog with A. In that case, having sent the answer from B, 
it cannot send the answer from C. It will have to answer C on its own 
and keep the results to itself.

Or, the B2BUA could pretend to be *two* UAs. Then it can send the answer 
from B using one to-tag, and the answer from C using a different to-tag. 
A will see this as forking and respond accordingly.

	Paul

> ------------------------------------------------------------------------
>