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.
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.
Solved! Go to Solution.
Well, it seems to be firmware bug. If you wish a Cisco employee will catch your report, then you should report it for latest firmware. Even in such case, your chances are not so high. But with bug report related to 7.5.1a, your chances are void ...
So many changes are not mentioned in Release Notes ...
Just my $0.02 ...
Is there some "reason header" in your CANCEL message?
I had a similar issue with don't stop ringing of SPA504. In my case the issue was caused from proprietary Microsoft reason header contained in SIP messages.
My suggestion is upgrade the firmware, test the scenario again and open a case to the STAC.
Yes, there is a reason header present in the cancel request. The reason header is, however, correct according to the SIP RFC. We use kamailio for SIP routing, not proprietary software.
To be certain, I reproduced the error, while having all reason headers removed, and the same problem occured.
We have retried the scenario with newest firmare (7.5.5), and the problem persist. I have also opened a case to the STAC as you suggested!
Thanks for you suggestion and feedback!
By the way, it would be nice if someone will report the regression of CDET CSCty82148 to SMB TAC. Unfortunately, I'm unable to do it by self as they don't accept written reports and I can't speak online with them.