My thoughts are below. Hope it helps. Regards,
Indresh -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Yong Xin Sent: Wednesday, March 28, 2007 1:34 PM To: [email protected] Subject: [Sip-implementors] SIP Contact header Hi, As per RFC 3261, the UAS MUST add a Contact header field to the 2xx response to the INVITE. The Contact header field contains an address where the UAS would like to be contacted for subsequent requests in the dialog (which includes the ACK for a 2xx response in the case of an INVITE). My questions are: 1) Would the ACK for a non-2xx response be using this contact address? (I assume not. My understanding is that UAC must send ACK for a non-2xx response using the same destination address as the INVITE) >> No. Your understanding is correct. ACK for 3xx-6xx responses are sent to the same address where original request was sent. For e.g consider the redirection case where the contact would be different, but the ACK should go to the original destination which redirected the call for him to cease retransmission. 2) How about PRACK or UPDATE request which is sent from UAC to UAS before the dialog is established (i.e.: 200 ok to INVITE is not sent by UAS yet)? (I assume same as the ACK for non-200 response). >> PRACK/UPDATE would be sent after an early dialog is established. >> In that case the dialog layer "remote-target-URI" information is used to send the requests. >> Dialog layer remote-target-uri for the UAC will contain the address where the original INVITE >> was sent and later after receiving the 200OK the remote target URI MUST be updated ( Page 75 RFC-3261 ) >> Now based on this PRACK/UPDATE on early dialog would go to same address where original INVITE was sent. Your comments are appreciated. Thanks, Yong _______________________________________________ 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
