I prefer method 4. This is also the requirement of some big service provider's application(e.g. China Telecom CRBT application). Note the media attibute in 183 should be set to "sendonly". Regards, Zhifeng
-----Original Message----- From: Christer Holmberg (JO/LMF) [mailto:[EMAIL PROTECTED] Sent: 2006年10月2日 20:57 To: [EMAIL PROTECTED]; [email protected] Cc: [email protected] Subject: RE: [Sip] Early media query Hi, You can use Method 2, assuming the 18x and 200 have different To tag values. Otherwise you can use Method 3 or 4 (message 9 in Method 3, and message 7 in Method 4, seem to go in the wrong direction, though). Regards, Christer _____ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Sent: 2. lokakuuta 2006 12:57 To: [email protected] Cc: [email protected] Subject: [Sip] Early media query Hi, I want to made an application where we can use early media for playing initial in-band announcements, and then finally connecting the caller to actual callee (eg prepaid card application). I want to know which is the correct way to support this as per SIP RFC. Method 1: Caller Callee | | | | |(1) INVITE with offer | |---------------------------->| | | | | |(2) 183 with answer 1 | |<----------------------------| | | | | |(3) 200 OK with SDP | |<----------------------------| | | | | |(4) ACK | |---------------------------->| | | (2) contains SDP of announcement server (3) contains SDP of callee Method 2: Caller Callee | | | | |(1) INVITE with offer | |---------------------------->| | | | | |(2) 183 with answer 1 | |<----------------------------| | | | | |(3) PRACK | |---------------------------->| | | | | |(4) 200 PRACK | |<----------------------------| | | | | |(5) 200 INVITE with sdp | |<----------------------------| | | | | |(6) ACK | |---------------------------->| | | | | | | | | (2) contains SDP of announcement server (5) contains SDP of callee Method 3: Caller Callee | | | | |(1) INVITE with offer | |---------------------------->| | | | | |(2) 183 with answer 1 | |<----------------------------| | | | | |(3) PRACK | |---------------------------->| | | | | |(4) 200 PRACK | |<----------------------------| |(5) 200 OK | |<----------------------------| | | |(6) ACK | |---------------------------->| | | |(7)Re-INVITE with SDP | |<----------------------------| | | | | |(8) 200 OK with SDP | |---------------------------->| | | |(9) ACK | |---------------------------->| (2) contains SDP of announcement server (5) contains no SDP (7) contains SDP of callee (8) contains answer of caller for callee offer Her, UDATE can also be used instead of Re-invites. Method 4: Caller Callee | | | | |(1) INVITE with offer | |---------------------------->| | | | | |(2) 183 with answer 1 | |<----------------------------| | | | | |(3) PRACK | |---------------------------->| | | | | |(4) 200 PRACK | |<----------------------------| |(5) UPDATE (callee offer) | |<----------------------------| | | |(6) 200 UPDATE (answer) | |---------------------------->| | | |(7) 200 INVITE | |---------------------------->| | | |(8) ACK | |---------------------------->| In this case, when callee answers, UPDATE is sent to caller to negoitate audio with caller, and then 200 OK is sent for the initial INVITE. Regards, Udit _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
