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Problem when sending CANCEL before 180 Ringing is received

We're experiencing a problem with Cisco SPA504 and SPA525, which causes SPA phones to keep ringing, when a call is initiated and cancelled directly after. The problem is described in the SIP flow chart below, one working flow and one which causes problems.

cisco-sip-flow.png

Whenever a CANCEL request is dispatched before a "180 Ringing" respond, the phone respond with a "481 Call Legg/Transation Does Not Exist". And even though the PBX resends the CANCEL request after the "180 Ringing", it still get the reply "481 Call Legg/Transation Does Not Exist".

According to the SIP RFC, I understand that, a dialog can be cancelled after the first informational response (1xx), which obviously isn't the case for Cisco SPA phones.

We're running firmware 7.5.1a. I know there are newer versions, but we have not seen anything regarding this in the change logs.

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ffacilities
Beginner

Has anybody been able to see whether the problem can be reproduced in the newer 7.5.7 FW?

Thanks,

Jack

Jack,

I've been able to reproduce the issue with 7.5.7 firmware, so yes it has not yet been fixed.

At least I've had confirmation from Cisco that they are able to reproduce the issue.. now the wait on the fix.