You're missing several messages in the flow below. If the UPDATE extension is supported by User A and the AS then you can have User A send its media to User B using UPDATE. Otherwise, the AS needs to reINVITE User A. But both INVITE transactions below need to complete with the AS. No ACKs go directly between User A and B. Have a look at draft-ietf-sip-update-02.txt, draft-ietf-sipping-3pcc-00.txt, draft-ietf-mmusic-sdp-offer-answer-02.txt, and of course draft-ietf-sip-rfc2543bis-09.txt.
Regards, Bert JayH. Kim wrote: Hi, all According to the SDP handling rules described in section 13.2.1 [Creatingthe Initial INVTE] of bis-09, the UAC must treat the first SDP it receives as the answer, and must ignore any subsequent SDP answers. But If I consider the case of Prepaid Card Service, the description in section 13.2.1 make me some confusion. 1. User A dial the Prepaid Card Serivce number 2. The session is directed to the application server(AS). 3. The AS propmt to get the destination information. 4. The User A says the destination number. (TTS) 5. The AS direct the session to the destination. If the AS actively collect the destination information, the audio data in RTP should be transfered to the AS. So, I think, the AS can add the SDP for its own to collect the information. But this SDP can be different that of the UAS, destination. User A AS User B | INVITE with SDP_A | | |-------------------------->| | | | | | 183 with SDP_AS | | |<--------------------------| | | | | |<== 'Give me your destination' | | | ==> 'amazon.com' | | | | INVITE with SDP_A | | |--------------------------->| | | | | 200 with SDP_B | 200 with SDP_B | |<--------------------------|<---------------------------| | | | ACK | |------------------------------------------------------->| | | Could anybody tell me is there any misunderstanding or wrong assumption in my thought? Thanks forward. Regards, Jay --------------------------------------------------------- Jay H Kim R&D Center XENER Systems Inc. Office: +82-2-3482-4900. ext.411 Fax: +82-2-3483-4902 +mailto:[EMAIL PROTECTED] Homepage: www.xener.com -------------------------------------------------------- _______________________________________________ Sip-implementors mailing list [EMAIL PROTECTED] http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
