[Users] call drop in a few seconds

Daniel-Constantin Mierla daniel at voice-system.ro
Thu Feb 2 17:00:35 CET 2006


On 02/02/06 17:28, unplug wrote:
> Thanks for explanation.  As a normal user behaviour, he will cancel
> the call when he noted that he has dialed a wrong number.  Then he
> will make another call for his desired destination immediately.
> As you said, UA1 needs to wait until the message cycle complete. 
> However, user have no idea when the message cycle will complete. 
The user should not be the one to solve the problem. The UA1 device has 
to behave properly, to keep the canceled dialog until the cycle 
completes. Moreover, it should match the BYE to the proper dialog or 
send back "call/leg transaction does not exist" when the call is no 
longer active.
>  For
> a long distance call, the time needed for completing the cycle will be
> much longer.
> Do you mean it can't be prevented in the voip/openser environment?
>   
I would say no. In similar case to UA1 may be a gateway or multi-line 
phone which can have several calls in parallel. The UA1 must follow 
dialog matching specifications as per RFC3261 and everything should go 
just fine.

Cheers,
Daniel

>
>   
>> such situation is hard to prevent from proxy side. In my opinion, the
>> UA1 does not behave correctly. After UA1 sends the CANCEL, it has to way
>> for 200OK of CANCEL and 487 for INVITE and then send the ACK for
>> INVITE's reply. Only after all these messages , it can close the dialog
>> to UA2 and not the one to UA3.
>>
>> Basically, the UA1 matches the wrong dialog for BYE (the From tag in BYE
>> (UA2) should be different than the tag of UA3).
>>
>> Cheers,
>> Daniel
>>
>>     
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