Scenario 2: A must send ACK to B since all transactions MUST be terminated. Then A can send BYE to B instead of CANCEL because the 200 has already be received.
----- Original Message ----- From: "James" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Tuesday, August 13, 2002 4:19 PM Subject: [Sip-implementors] Call Flow problem > Hello All, > > Think about the scenarios below : > > 1) User A calls User B , User B responses with 180, at the same time , User C calls > > User A, and User A does want to talk with User C ,what should User A do ? > > I think : User A should CANCEL User B first( the dialog between A and B is not >setup yet,the Three HandShake INVITE/200/ACK is incomplete), and response User C with >200 OK, right? > > +---------+ +-----------+ +--------+ > | User A | | User B | | User C | > +---------+ +-----------+ +--------+ > | | | > | 1. INVITE | | > |------------------------->| | > | 2. 180 | | > |<-------------------------| 3. INVITE | > |<-------------------------------------------------| > |User A want to talk with User C | > | 4. 180 | | > |------------------------------------------------->| > | 5. CANCEL | | > | ------------------------>| | > | 6. 200 | | > |<-------------------------| | > | 7. 487 | | > |<-------------------------| | > | 8. ACK | | > |------------------------->| | > | 9. 200 OK | > |------------------------------------------------->| > > 2) Comparing with 1) , User A calls User B , User B responses with 200 OK, and User >A has not sent ACK to User B, at the same time , User C calls User A, and User A does >want to talk with User C ,what should User A do ? > +---------+ +-----------+ +--------+ > | User A | | User B | | User C | > +---------+ +-----------+ +--------+ > | | | > | 1. INVITE | | > |------------------------->| | > | 2. 200 OK | | > |<-------------------------| 3. INVITE | > |<-------------------------------------------------| > | User A want to talk to User C > | What should User A do ? send BYE to User B ? > if User A sends BYE to User B , but the Three Handshake INVITE/200/ACK is >also > incomplete( no ACK). > I think , User A should send CANCEL to User B ,right? > > > Thank you to give me an answer! > > > _______________________________________________ > Sip-implementors mailing list > [EMAIL PROTECTED] > http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors _______________________________________________ Sip-implementors mailing list [EMAIL PROTECTED] http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
