[SIPForum-discussion] 481 Transction Does not Exist & ACK for 200 OK

[Raghul Prasanna]

Hello All,
 
I have the following scenario.
 
Application Server Sends ACK to 200 OK from an SBC.  But due to network delay, the ACK took several mins to reach the SBC and the SBC in the meantime crashed and rebooted, so lost its session.
 
When it received the ACK for the 200 OK it sent before the crash, it didnt relate to any of its session as it had crashed and recovered a min ago.
 
I expected the SBC to return 481 Transaction\Dialog does not exists or some of form of indication to the App Server, stating it doesnt understand, but nothing came back. So as far as the App server was concerned, the call got established.
 
What can be done in this situation? Is it true that 481 message will be returned only for SIP message, that requires a response and in this scenario ACK doesnt trigger any response, so we shouldnt be expecting any message from SBC that it doesnt understand the transaction? 
 
If someone thinks that its wrong and SBC should have responded with a message clearly saying I dont understand what you are saying to me, then please lemme know and if any rfc points to this, let me know that as well please?
 
Any input will be really helpful.
 
Thanks,
Raghul


      
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