Hi Dale, Thank you very much. Its clear now. I found one as well under 3261 under Paragraph 15.
On Fri, Jun 9, 2017 at 8:04 PM, Dale R. Worley <wor...@ariadne.com> wrote: > NK <nitinkapo...@gmail.com> writes: > > I am facing a strange scenario where my SBC is sending BYE before it > > received 200 OK for initial invite. > > > > A ========= INVITE ========> B > > A <=== 100 Giving a Try ========B > > A <==========100 Try ========B > > A <======183 w/SDP==========B > > A <======183 w/SDP==========B > > A <======180 w/SDP==========B > > A ========= *BYE* ==========> B > > A <=== *SIP 200 OK for Invite* ====B > > I take it that "my SBC" is the same as "A"? You really should use > consistent terminology, or explain this. > > > Anyone faced this problem earlier? Is that possible because i believe we > > should receive only CANCEL to terminate the call before the dialog > > establish. > > > > Can any one please help on this? And if there is any rfc can help me to > > understand this. > > It looks like the first paragraphs of section 15 of RFC 3261, > "Terminating a session", address this. The critical point is that while > the UAC sending CANCEL attempts to terminate the effect of the INVITE, > that is, all active forks of it, a BYE terminates only the *dialog or > early dialog* it is sent on. That is, a BYE has a to-tag, and it only > affects the (early) dialog with the UAC that sent the (provisional) > response(s) with that to-tag. > > So to address your case, you'd need to specify what to-tags are present > in the responses. I suspect that all of them have the same to-tag, so > there's one early dialog starting at the first 183 that would become > established with the 200 for INVITE, but it's terminated by A sending > the BYE. > > As always, when dealing with strange cases of the SIP protocol, it's > worth checking RFC 5407, "Example Call Flows of Race Conditions", which > is so significant it is sometimes referred to by just the name of its > primary author, "Hasebe". It gives more detailed state machines for the > UAS and UAC. In this case, I find "Appendix A. BYE in the Early > Dialog", whose text refers to section 3.1.3, "Callee Receives BYE (Early > State) While in the Moratorium State". > > Dale > _______________________________________________ Sip-implementors mailing list Sip-implementors@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
