A Contact is required for dialog establishing requests (and their 2xx response) and in-dialog target refresh requests (and their 2xx response). REFER is a dialog establishing request (when it does not have a to-tag). Also, normally, REFER creates an implicit subscription and the Contact is needed by the UAS to know how to address the NOTIFY.
Cheers, (-:bob -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Iñaki Baz Castillo Sent: Wednesday, February 04, 2009 5:11 AM Cc: [email protected] Subject: Re: [Sip-implementors] [Sip] Is Contact Header mandatory in REFER message? 2009/2/4 Avasarala Ranjit-A20990 <[email protected]>: > Yes, Contact header is required for all SIP Messages. Not at all. Contact is just required for requests creating a dialog (INVITE, SUBSCRIBE) for registering a contact (REGISTER), for 3XX replies, for 2XX replies to a request creating a dialog (INVITE, SUBSCRIBE), 2XX from a registrar. There is also some confusion about the requeriment (or not) of Contact in a 1XX response (for an INVITE). If a 1XX (non 100) has no Contact then in-dialog messages (even if early dialog) from UAC to UAS wouldn't be possible (INFO, PRACK...). 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
