Hi, The 2xx is transmitted through the Proxy while the ACK for this 2xx will be sent/recv directly between the UAC and UAS. So to ensure the correct behavior on stateful proxy, the transaction layer should be destroyed once the Transaction goes to "Terminated". The TU (Core) will be responsible for the 2xx retransmission.
And for the retransmitted Invite, the TU should be responsible for discarding this message with the same "CALLID + From tag" as an established dialog. Alex Zhang ESN: 6-554-8782 -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of I?aki Baz Castillo Sent: Monday, March 10, 2008 6:04 PM To: [email protected] Subject: [Sip-implementors] Why 2XX retransmissions for INVITE ServerTransaction is handled by TU? Hi, please, could someone explain me why the server transaction MUST be destroyed when TU passes a 2XX to it? What is the benefict? I read "this is needed to ensure reliability of the 2xx responses to INVITE" but can't understand why. In fact, if UAS receives an INVITE and accepts it by passing a 2XX, and inmediately the server transaction is destroyed, what would occur if a retransmited INVITE arrives? the server transaction has been destroyed so will the INVITE arrive to the TU? is it? how to drop it since it's obviously a retransmission but the server transaction (the entity which handles retransmissions) has been destroyed? ------------------------------------------------------------------- 17.2.1 INVITE Server Transaction If, while in the "Proceeding" state, the TU passes a 2xx response to the server transaction, the server transaction MUST pass this response to the transport layer for transmission. It is not retransmitted by the server transaction; retransmissions of 2xx responses are handled by the TU. The server transaction MUST then transition to the "Terminated" state. [...] Once the transaction is in the "Terminated" state, it MUST be destroyed immediately. As with client transactions, this is needed to ensure reliability of the 2xx responses to INVITE. ------------------------------------------------------------------- Thanks a lot for any explanation. Best regards. -- Iñaki Baz Castillo [EMAIL PROTECTED] _______________________________________________ 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
