For (1), Proxy1 should re-transmit if it is a stateful proxy. For (2), the UAS is responsible for re-transmitting its response, proxies don't retransmit responses (unless the proxy generated them - ex 408). For (3), yes, the UAS should retransmit a response if it receives a re-transmitted request. -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] Sent: Saturday, August 04, 2001 2:45 PM To: Hearty, John Cc: [EMAIL PROTECTED]; [EMAIL PROTECTED] Subject: RE: [Sip-implementors] Query on tags in From field and Retransmis sion of INVITE responses in TCP !! Hi, I have similar questions on Retransmission over TCP, Section 14.4.2, bis-4. Suppose the following scenario. [A] --- TCP---- [Proxy1]------UDP ----- [Proxy2] ----TCP------[B] (1) A sends an INVITE which gets eventually proxied to B. B doens't send any response. Does Proxy1 retransmit INVITE following retransmission algorithms used for UDP? (2) A sends an INVITE which gets eventually proxied to B. B sends 200 OK which gets eventually forwarded to A. A doesn't send ACK. Does Proxy2 retransmit 200 OK following retransmission algorithms used for UDP? (3) Section 14.3,2, Reliable Transport Protocol, does not say anything about retransmission of responses for non-INVITE messages. Does the UAS using TCP need to retransmit a final response when receiving a retransmitted non-INVITE request? YoungSun [EMAIL PROTECTED] on 07/26/2001 01:41:05 PM To: [EMAIL PROTECTED], [EMAIL PROTECTED] cc: (bcc: Youngsun Song/Telcordia) Subject: RE: [Sip-implementors] Query on tags in From field and Retransmis sion of INVITE responses in TCP !! Here is the explanation in bis-04 for re-transmitting responses: 14.4.2 Reliable Transport Protocol A user agent using a reliable transport protocol such as TCP, SCTP or TLS MUST NOT retransmit requests, but uses the same algorithm as for unreliable transport protocols (Section 14.4.1) to retransmit responses until it receives an ACK. A client MAY give up on the request if there is no response within a client-defined timeout interval. It is necessary to retransmit 2xx responses as their reliability is assured end-to-end only. If the chain of proxies has an unreliable transport protocol link in the middle, it could lose the response, with no possibility of recovery. For simplicity, we also retransmit non-2xx responses, although that is not strictly necessary. -----Original Message----- From: Viswanathan, Sriram C (Sriram) [mailto:[EMAIL PROTECTED]] Sent: Thursday, July 26, 2001 11:16 AM To: [EMAIL PROTECTED] Subject: [Sip-implementors] Query on tags in From field and Retransmission of INVITE responses in TCP !! Hi, I have question on the RFC related to the "From" field. In the "From" field there is a requirement to define a "tag" parameter (MUST). I am unable to create a scenario wherein this would be required from the UAC perspective. Also, could anyone indicate as to why the retransmission of INVITE responses are done for a TCP connectivity. TCP itself is a reliable transport. Even if we have intermediate proxies or other carriers I am assuming that when they implement UDP on the way, they would have retransmission logic built in. The other thing is if a SIP message indicates that the transport is TCP and if any proxy on the way does not support this transport there is supposed to be an error code returned back. Is this correct? Would appreciate if anyone could throw some light on this or even if possible any web site which indicates a link to this kind of info. Thanks, Sriram _______________________________________________ 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
