P�ter,
Such questions should be discussed on the sip implementors list, so I am posting the reply there rather than the sip list.
P�ter Barta wrote:
Dear All,
as I understood from RFC 3261 and from various posts of this list, a B2BUA is basically two SIP UAs with no clear definition of how they interact or work together to manage sessions through the B2BUA.
Yup.
Does the B2BUA terminate sessions completely, so sessions are completely independent on the two session legs?
Maybe, maybe not. Both kinds are possible and useful.
If yes, it means that all session related descriptors have to be changed. How does the B2BUA then match the two legs?
There are some attributes that can't be kept synchronized on the two sides. CSeq is one of them. Unlike a proxy, in general a B2BUA must be dialog stateful. So it can keep a table of values for each side, and correlate based on dialog id.
You can do the exercise of trying to find a way to make a stateless B2BUA. I think you will find that no matter how hard you try you can't do it.
Is there some parameter that remains unaltered? If, e.g., Call-ID would remain the same then it were easy to correlate the signaling legs, but otherwise the B2BUA has to maintain some kind of mapping to identify that certain legs belong to the same session.
Is this behavior specified somewhere?
No. At least not in the IETF.
Paul _______________________________________________ Sip-implementors mailing list [email protected] http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
