I guess the original question was 'When does a UA send an OPTIONS message in an established session ?'
Anyway, the SIP specification does not put any limits on sending the OPTIONS message with in/ outside the dialog. Typically, a UAC can send an OPTIONS message after it has recieved a 200 OK response form the UAS but before sending the ACK. Another possible scenario is that the UAC might require to enquire capabilities before it sends a RE-INVITE message with in the established session. E.g. A CODEC preference change. Some UAC implementations even send the OPTIONS message on a periodic basis to the proxy as a keep-alive mechanism to ensure that the link to proxy is still active. Hope this information helps. regards, Gaurav -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Vijay Shanmugam Sent: Tuesday, December 21, 2004 4:48 AM To: edison Cc: [EMAIL PROTECTED] Subject: Re: [Sip-implementors] Hello!A question about OPTIONS. Hi, The SIP method OPTIONS allows a UA to query another UA or a proxy server as to its capabilities. This allows a client to discover information about the supported methods, content types, extensions,codecs, etc. without "ringing" the other party. For more details refer section 11 in RFC 3261. Thanks & regards, Vijay Shanmugam 2476, Swedesford Road, Malvern, PA 19355. Ph: 610 648 4547 [EMAIL PROTECTED] wrote: ----- To: <[EMAIL PROTECTED]> From: "edison" <[EMAIL PROTECTED]> Sent by: [EMAIL PROTECTED] Date: 12/20/2004 02:23AM Subject: [Sip-implementors] Hello!A question about OPTIONS. Hi!! First,I apologized for my poor English. Two UAs are established a session already.Rtp packages are send end-to-end.But ,sometimes one of the UAs will send a OPTIONS. I just don't understand they send OPTIONS packages in what situations? Thanks for reading. _______________________________________________ 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
