Hello Hemanth, According to RFC3262 section 5 the below statement
"If a reliable provisional response is the first reliable message sent back to the UAC, and the INVITE did not contain an offer, one MUST appear in that reliableprovisional response." UAS MUST send Offer in 183 response In your scenario I suggest the B2BUA to terminate the call by sending CANCEL to UE2 and 487 response to UE1. Thanks & Regards, Sreenath ________________________________ From: "Kumar, Hemanth" <[email protected]> To: "[email protected]" <[email protected]> Cc: Paul Kyzivat <[email protected]> Sent: Friday, 6 January 2012 1:52 PM Subject: Re: [Sip-implementors] Expected UAC behavior when a reliable/non-reliable 18x without SDP is recieved for an INVITE sent without an offer and require 100 rel Hi All, This is a B2BUA scenario. This issue is as shown below UE1 ----- INVITE [no SDP, Require:100 Rel] ------------ > B2BUA ------- INVITE [no SDP, Require:100 Rel] -----------> UE2 B2BUA <------- 183 [no SDP] ------------- UE2 When an INVITE is sent with require 100rel and without an offer, misbehaving UE2 sends 18x without SDP. RFC 6337 does not define the behavior of UAC in this case. There could be 2 possible solutions: 1. Tear down the call by sending CANCEL on egress leg and 420 Bad extension response on ingress leg as shown below UE1 ----- INVITE [no SDP, Require:100 Rel] ------------ > B2BUA------- INVITE [no SDP, Require:100 Rel] -----------> UE2 UE1 <----- 420 Bad extension ------------------------------ B2BUA<------- 183 [no SDP] ---------------------------------- UE2 B2BUA ------- CANCEL ------------------------------------------> UE2 2. Ignore 18x received and wait for reliable response containing SDP on the egress leg. On receiving the response, send 18x reliably with SDP followed by 200 OK with the same SDP on the ingress leg. This ensures backward compatability. UE1 ----- INVITE [no SDP, Require:100 Rel] ------------ > B2BUA ------- INVITE [no SDP, Require:100 Rel] -----------> UE2 B2BUA <---------- 183 [no SDP] ---------------------------------- UE2 UE1 <----- 183 [with SDP] --------------------------------- B2BUA <----------- 200 [with SDP] ------------------------------ UE2 UE1 <----- 200 [with SDP] --------------------------------- B2BUA I would appreciate if you could share your comments on both the solutions and propose alternate solution if any. Regards Hemanth -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Kumar, Hemanth Sent: Wednesday, January 04, 2012 8:39 PM To: [email protected] Cc: Paul Kyzivat Subject: [Sip-implementors] Expected behavior for an INVITE sent without an offer Hi, What should be the behavior of UAC when an INVITE is sent without offer and Require 100rel and it receives non-reliable/reliable 18x response without SDP? Should the transaction be terminated by sending CANCEL? The same scenario was given as comment which has not been addressed in offer/answer draft-ietf-sipping-sip-offeranswer-03 http://www.softarmor.com/sipping/process/wg-review/reviews/draft-ietf-sipping-sip-offeranswer-03-seth.txt " 3. Section 1.1 : Comment :- We should define the behavior for a UAC which sends out an INVITE without SDP and receives the first non-failure reliable response without an Offer, due to the UAS not conforming to the draft. As this being an open point can lead to multiple different implementations. Does the UAC clear the call or send a PRACK and wait for the offer in subsequent reliable responses." _______________________________________________ Sip-implementors mailing list [email protected]<mailto:[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 _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
