Session timers can be used as keep alive mechanisms for FW's and possibly as a way to detect stale connections (ie. no response to reinvite means the session is stale). For these reasons a UA may want to send session refreshes to a UA that doesn't support it.
Note: All UA's must respond to reINVITE messages (RFC3261). If a UA doesn't support session timers, they should still respond to a session refresh normally. -----Original Message----- From: ira kadin [mailto:[EMAIL PROTECTED] Sent: Wednesday, December 08, 2004 4:48 AM To: [EMAIL PROTECTED] Subject: [Sip-implementors] RE: Session timer Hi All, I have a question regarding supporting the session timer (draft from July 18, 2004). >From one side it's written that "A UAC that supports the session timer extension defined here MUST include a Supported header field in each request (except ACK)" >From other side on page 18 there is a table, indicating the UAS behavior UAC supports? refresher parameter refresher parameter in request in response ------------------------------------------------------- N none uas N uac NA N uas NA Y none uas or uac Y uac uac Y uas uas >From line N1 we can see that if "timer" supported header doesn't exist in INVITE, the UAS may include it in 200 response. And visa versa. It is possible that the UAC requested session timer (and thus included a Session-Expires header field in the request), but there was no Require or Session-Expires header field in the 2xx response. This will happen when the UAS doesn't support the session timer extension, and only the UAC has asked for a session timer (no proxies have requested it). In this case, if the UAC still wishes to use the session timer (they are purely for its benefit alone), it has to perform them. Does it mean, that UAS or UAC has to send UPDATE/RE-INVITE to the non-supported timer side and "cut" the session if 200 reply is not received (why should it be received if other side doesn't support it) ? I hope I explained the problem Thanks in advance Ira _______________________________________________ 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
