Disallow 180 Ringing after 183 Session Progress?

Hi, I’m using Asterisk 11.13.1.

I’ve got an issue with Asterisk and Cisco/Linksys phones.

To explain:

My setup: IP-Phone -> Asterisk -> Mediant2000 -> PSTN

Let’s say that this Cisco SPA504G IP-Phone places a call to a mobile number which is currently switched off. In this case, the carrier sends a voice message in early media “The subscriber’s phone is switched off or out of the coverage…”

Asterisk sends 183 Session Progress with SDP to Cisco SPA504G offering to establish an audio path for the carrier’s message. But then, immediately after that it sends 180 Ringing which confuses Cisco SPA504G and instead of playing the carrier’s message to the caller, it plays local ringing to the caller, which is not acceptable.

Also Linksys SPA922 exhibits the same kind of behavior.

I tested a few softphones and a Fanvil phone and they seemed to not care about the 180 Ringing, but Linksys/Cisco do. Afaik we have like 500 such IP-Phones and it really annoys users to hear generic ringing instead of meaningful messages.

Is there any way to suppress 180 Ringing after 183 with SDP? It doesn’t make much sends to send 180 after 183 at all if the early media path has been established.

Could anybody help with this? I am really struggling to find a solution.

Don’t receive them on the incoming side!

This is happening either because of something you have done in the dialplan, or something the upstream system is sending, but you haven’t provided your dialplan or a trace of what the upstream system is sending.