[OpenSER-Devel] [Serdev] Possible bug in the tm module in the presence of packet loss/branches

[Klaus Darilion]

Dan Pascu schrieb:
> That is not the case. If a 200 OK happens to come at the same time with 
> the CANCEL and there is a race condition and the call does get setup and 
> charged, I can explain my subscriber that he happened to put the call on 
> hook at the same time it was answered by the other side and it was just 
> the fact that it was answered while he was placing it on hook. He can 
> understand that.
> 
> But if I tell my subscriber that he has put the phone on hook effectively 
> canceling the call, but a 200 OK came out of nowhere 10 seconds later and 
> did setup a session despite the user indicating it has no intention to 
> carry on with it, that there was no race condition, but simply the system 
> ignored his request because there was packet loss and the RFC mandates 
> that it has to wait for some timers to expire, that he won't understand.

You are right!

> Try to tell your subscribers that your wonderful next generation VoIP 
> system takes away their ability to cancel a call, that it may randomly 
> (based on network packet loss) decide to setup a call at a later time 
> despite the user canceling it, and do this based not on an understandable 
> race condition situations, but on purpose, and see how many of them would 
> want to use your system.

Dan, you should post this example on the SIP-implementors mailing list. 
I wonder what the SIP experts will say to this examples.

regards
klaus