Concerning the lack of Contact within a dialog created by an INVITE 18x with To tag, it means that the UAS is non compliant to RFC 3261. The non compliance can be because of the following 3 reasons (and maybe more).
1) UAS is unintentionally being non compliant because a prior 18x creating the dialog and containing the Contact was not received by the UAC. Some vendors intentionally behave this way as an optimization or other reason; however it can cause interoperability issues and the potential non compliance. 2) RFC 2543 allowed the Contact to be optional within some situations. If assume that is the reason for missing Contact, you can follow RFC 2543. 3) UAS is non compliant because thinks RFC 3261 indicates that the INVITE 18x tag and Contact creates a dialog instead of just the INVITE 18x with To tag. If you assume number 2 is reason, you can build the BYE per RFC 2543. If you assume numbers 1 or 3 are the reason, you can basically do whatever you want; this includes potentially not attempting to send requests over the early dialog because the UAS was non compliant. ________________________________________ From: Iñaki Baz Castillo [[email protected]] Sent: Tuesday, July 26, 2011 5:50 PM To: Brett Tate Cc: Pavesi, Valdemar (NSN - US/Irving); [email protected] Subject: Re: [Sip-implementors] BYE before call answer 2011/7/26 Brett Tate <[email protected]>: > If your are still talking about early dialogs, the early dialog was created > by receiving a 18x with To tag. The caller can send BYE over an early dialog. If the 180 has no Contact header (and possibly it does not mirror the Record-Route headers added by proxies) how would the UAC construct the BYE for that dialog? Yes, I know that the UAC could construct it with the original INVITE RURI, the From/To tags and send it to the proxy. Then the proxy would do parallel forking.... for a request with To tag? Not at least any proxy configured by me. Regards. -- Iñaki Baz Castillo <[email protected]> _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
