Christina, See RFC3261, section 14.2, page 89. To quote...
If a UAS generates a 2xx response and never receives an ACK, it SHOULD generate a BYE to terminate the dialog. So UA Y should have BYEd the session. It is possible that for some reason the BYE never reached X in which case Y believes the session is gone. For the second re-INVITE I would therefore have expected a 481 not a 400. So to answer your questions, in step 7, the UA (X) can reINVITE because it has no way of knowing that the ACK didn't reach UA Y. In step 8, I would have expected a 481 error, but a 400 might occur - I would need to see the actual messages exchanged to comment further. FYI, if the UA (Y) believed that the reINVITE of step 4 were outstanding, it should have sent a 491 response to the reINVITE of step 7 (as per RFC3261, 14.2). Paul D.Smith Network Protocols Group Data Connection Ltd (DCL) Tel: +44 20 8366 1177 Email: [EMAIL PROTECTED] Fax: +44 20 8363 1039 Web: http://www.dataconnection.com -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Christina Zhao Sent: 15 July 2004 17:31 To: SIP (E-mail) Subject: [Sip-implementors] question for re-re-invite I met a problem when I study the SIP Spec. Can anyone give me his/her advice for that? Thanks a lot. The scenario is: 1. UA Y invited UA X. 2. UA X 200ed UA Y. 3. UA Y acked UA X. (SIP Session is established) 4. UA X re-invited UA Y. 5. UA Y 200ed UA X. 6. UA X acked UA Y. (It seems that UA Y doesn't get it because UA X receives retransmission of 200 in step 9) 7. UA X re-invited UA Y AGAIN (Is it valid?) 8. UA Y 400ed UA X. (Is it valid?) 9. UA X received retransmission of step 5. Q1: For UA X, we think step 7 is valid because the first re-invite transaction is already over, is that true? Q2: We are not very clear about step 8. For UA Y, the 2nd re-invite comes before it receives ack of 1st re-invite. What should UA Y do? Regards _______________________________________________ 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
