[Serusers] 408 to Caller UA when CANCEL to Callee

[Tulika Pradhan]

hi,

i am facing the following situation.

UA1 calls a user(UA2)  who does not answer. the control comes to 
failure_route where i try another UA (UA3). but as UA3 rings, SER sends 408 
Request timeout to UA1 and call gets disconnected.

this is the SIP message flow.

UA1                     SER                      UA2                        
UA3
INVITE---------------->
                               INVITE-------------->
                                <----------------TRYING
                                <----------------RINGING
<------------------RINGING


                              CANCEL-------------->
<---------------------408
                              
INVITE---------------------------------------->
                               <---------------------487
                              ACK------------------->
                                <-----------------------OK
                                 
<-------------------------------------------TRYING
                                
<--------------------------------------------RINGING

(but UA already has got the busy tone) and does not hear this ringing.

if 408 was not sent to UA1, then the call could have been established.

what is going wrong,

regards,

tulika