[OpenSIPS-Users] Transfer issue

Bogdan-Andrei Iancu bogdan at voice-system.ro
Tue Nov 17 10:28:06 CET 2009

Hi Iñaki,

Iñaki Baz Castillo wrote:
> El Lunes, 16 de Noviembre de 2009, Bogdan-Andrei Iancu escribió:
>> I agree that a b2bua is more complex than a proxy, but I guess the idea 
>> is to identify all these buggy cases and fix them.
> A very important issue in most of the existing B2BUA's:
> Imagine the b2bua routes/generates the call to a proxy which does parallel 
> forking so b2bua receives two 183 with different To-tag and, of course, 
> different SDP (sess-id, sess-version...).
> The b2bua replaces the received To-tags in an *unique* new To-tag to be used 
> in the upstream leg.
> This is a bug since the UAC will receive two 183 with same To-tag but 
> different SDP so it must ignore the second SDP (a SDP cannot change during an 
> early-dialog).
are you sure about this behaviour ? is it stated by  RFC3261?
> I've issued this problem. The solution is "easy":
> For each received 1XX response (different To-tags) the b2bua must create so 
> many different To-tags for the 1XX it sends to the UAC.
> If the b2bua doesn't replace the To-tag then the problem automatically 
> dissapears, but then it's not a b2bua :)
it does change :)


Bogdan-Andrei Iancu

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