[Kamailio-Users] 487 Request Terminated and BYE

Hi, I am facing problem with handling CANCEL/487 Request Terminated in a case of a call hunting. The problem is that the call terminating carrier doesn't process the ACK properly and keeps sending 487 messages. Here is an example. Let's say UAC1 has the following rules of call hunting : 1. call +33123456 for 10s 2. call +33789456 for 10s Let's say that an incoming call to UAC1 triggers the call hunting. Here is a diagram : openSER -> Terminating Carrier (TC) : INVITE +33123456 ... (time out : +33123456 didn't answer in 10s, so openSER sends an INVITE to +33789456 - and let's say to an other Terminating carrier TC2 - and CANCEL the current INVITE to TC) openSER -> TC2 : INVITE : +33789456 openSER -> TC : CANCEL TC -> openSER : 487 Request Terminated openSER -> TC : ACK The problem is now TC doesn't process the ACK correctly and keeps sending 487. So, in the case of +33789456 answering the call (a 200 OK is sent to openSER), openSER will keep relaying the 487 to TC2 and TC2 will then send a BYE a terminate the call : TC -> openSER : 487 openSER -> TC : ACK TC -> openSER : 487 openSER -> TC : ACK TC2 -> openSER : OK openSER -> TC2 : ACK <-- The call is taking place --> TC -> openSER : 487 openSER -> TC : ACK openser -> TC2 : 487 (openSER relays the 487 once the call has been established to TC2) TC2 -> openSER : ACK TC2 -> openSER : BYE <-- Call is ended but should not --> According to the RFC, once a call has been OKed and a 487 is received, TC2 may go on with the call or send a BYE (up to it). So it behaves the right way (chapter 15. end of 3rd paragraph : "If the INVITE results in 2xx final response(s) to the INVITE, this means that a UAS accepted the invitation while the CANCEL was in progress. The UAC MAY continue with the sessions established by any 2xx responses, or MAY terminate them with BYE."). My question is then : is there a way to prevent this behavior when a terminating carrier doesn't behave correctly, either by preventing relaying of the 487 once it has been ACKed or once the call has been OKed (but I guess we are not RFC compliant then) ? Thanks Bye, Guillaume