2010/3/20 Olle E. Johansson <o...@edvina.net>: > > 18 mar 2010 kl. 12.34 skrev Iñaki Baz Castillo: >> Nothing special, the UAC should b able to receive such RTP (real >> audio) and render it to the human via the phone speaker. >> It's really common and 200% valid. > > As a best current practise, I would recommend first sending a 180 Ringing, so > that all involved applications can change state. The 183 could very well mean > an error message, so you can not assume that it means ringing. Not sending > 180 makes life very hard for gateways. You are also allowed to include sdp in > an 180 message and both send your preferred ring tone and change state in the > same message.
Who should send such 180 prior to the 183? This is, if Alice calls Bob (who after so many calls already hates Alice) and Bob's phone is down, then provider would reply an early-media message "the person you are calling hates you and has switched off the phone". This audio would come into a 183. Why should be a 180 required before? Also, there are cases in which the PSTN gateways reply a 183 followed by a 180. This makes crazy some phones which don't know what to render (real audio of 183 or artificial ringing requested by the 180). -- Iñaki Baz Castillo <i...@aliax.net> _______________________________________________ Sip-implementors mailing list Sip-implementors@lists.cs.columbia.edu https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
