2009/2/23 Vito Korleone <[email protected]>: > Hi everybody! I 'm a new member in this group of SIP people :-). > > So, here's my question, > > Why "we" need a B2BUA?? Can't we just have the same functionality if > we replace him with a proxy and insert the Record Route field to trace all > messages between the subscribers?? > > thanks, > > Nikos > >
Depends upon the application. A b2bua puts state "in the network" (logically) which is against the end to end design principle of SIP. In particular, it breaks the three way handshake as the ACK cannot go directly end to end. The ACK has to routed through the Back to Back Dialogs. There is no way for the UAS to know that the UAC did not get the OK. In practical terms, this means that an element in the middle of the network can fail and one end (i.e. the end that sent the ACK ) can have the mistaken impression that the other end saw it and thereby "imagine" that the call has been successfully set up whereas in fact it has not thus leaving the system in a "hung" state. Of course, if there is a human answering the call, he will notice something bad and hang up so many do not consider it such a big deal. On the other hand, there are several perfectly good reasons for wanting to have a B2BUA. It appears that people have pointed out several such applications later in this thread and hence I will refrain from adding to the list. Ranga. > > ___________________________________________________________ > Χρησιμοποιείτε Yahoo!; > Βαρεθήκατε τα ενοχλητικά μηνύματα (spam); Το Yahoo! Mail > διαθέτει την καλύτερη δυνατή προστασία κατά των ενοχλητικών > μηνυμάτων http://login.yahoo.com/config/mail?.intl=gr > > > _______________________________________________ > Sip-implementors mailing list > [email protected] > https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors -- M. Ranganathan _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
