Avasarala Ranjit-A20990 wrote: > Can u give me a use case where UAS wants to send both 183 and 180 one > after the other?
With different To-Tags there are lots of use cases: [UC1] Multiple "stacked" proxies / gateways: UAC GW1 PSTN-GW | | | |- INVITE->| | |< - 100 - |- INVITE->| | |< - 100 - | |< - 180 - | | | |< - 183 - | |< - 183 - | | [UC2] Parallel forking: UAC1 GW1 UAC2 UAC3 | | | | |- INVITE->| | | |< - 100 - |- INVITE->| | | |- - - - INVITE - - >| | |< - 100 - | | | | |< - 100 -| | |< - 180 - | | |< - 180 - | | | | | |< - 183 -| | |< - 183 - | | |< - 183 - | | | Therefore it could also happen that SDP in 200 OK differs from SDP in 183. And you could get multiple different 183 replies. And 180 AFTER 183. Even with the very same To-Tag there are reasons for doing so: [UC3]: Consider a call to a B2BUA. It sends 180, UAC starts playing RBT. B2BUA makes part of a large application, does some database lookup, discovers who you are - and sends out 183 "We are sooooo sorry..." [UC4]: UAC with integrated Voicemail. It starts sending one or more 180 replies, after a timeout the 183 announcement starts "The number you have dialed..." Best regards, Thomas Gelf
_______________________________________________ Sip-implementors mailing list Sip-implementors@lists.cs.columbia.edu https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
