may be due to early media as well , with the second ring back being played back by the remote end/pstn gateway , as Ben says , without the full scenario it's not possible to know exactly what causes this . IMHO , you should not really be playing a local ring back on receipt of an 183 .. 183 is just session progress , not really meant to start of a local ring back ...
-----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Franz Edler Sent: Thursday, January 20, 2005 9:56 AM To: 'Laura Meng'; [email protected] Subject: RE: [Sip-implementors] why 180 and 183 come back togather? From: Laura Meng Sent: Wednesday, January 19, 2005 1:59 PM > double ringback, it seem one from 180, another from 183, but why this two > response occure togather? is it because the proxy fork INVITE to a PSTN > phone as well as IP phone? Yes, this is due to forking. > if so, should the proxy forward all the 180/183 back? Yes. > if so, what a mass at the UA's end, it start a single phone to want > to talk to someone, but turn out maybe it could get a meeting there! In case of the first final response arriving at the forking proxy this proxy must cancel all other pending transactions. So in normal forking case the UAC will get more 18x responses but only one 200 (RFC 3261 16.7-10). I hope that helps Franz _______________________________________________ Sip-implementors mailing list [email protected] http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors _______________________________________________ Sip-implementors mailing list [email protected] http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
