As per section 2.1 of rfc 3666, the softphone should open the rtp port to receive early media when the gateway responds with 183 + SDP.
On Sat, Mar 20, 2010 at 6:52 PM, Olle E. Johansson <[email protected]> wrote: > > 20 mar 2010 kl. 13.43 skrev Iñaki Baz Castillo: > >> 2010/3/20 Olle E. Johansson <[email protected]>: >>> >>> 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). >> > In the case of using early media just to send a ring tone, I would prefer > sending 180 with SDP, > or 180 first, then 183 with SDP. I don't like devices that only send 183 with > SDP for ring tone. > > /O > _______________________________________________ > Sip-implementors mailing list > [email protected] > https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors > _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
