Can the UDP timeout value be changed? The MX does have a simple UDP timer function, which will drop a traffic flow after an extended period of inactivity. This timer cannot currently be changed. However, a timeout would require both peers to be completely silent for an extended period of time in order to take effect. UDP communication between peers on an active call, for example, is highly unlikely to be dropped due to a timeout.
A packet capture on the SIP trunk reveals the carrier sending a bye message because after X amount of time they are getting no response.
Re: VoiP calls being dropped after 30 minutes, UDP Timeout / NAT Pinhole timer causing the issue?
I personally never use UDP for VoIP because of issues like this (with lots of vendors kit). I personally use SIP/TCP/TLS - so everything is encrypted, but at a minimum, I would change to using SIP/TCP to get rid of your headaches.