I have a client who receives remote video from approx 1300 security cameras via DSL. The video comes in via UDP (ports 15000-15200). He has a Fortigate firewall and a Cisco 800 series router at the head of the network. The video connection stops working after 5 minutes of inactivity (i.e. no use of the relevant software) but can reconnect immediately. This happens on all connections whether instigated locally or remotely. If he connects from a standalone DSL line with modem only no timeout occurs. He also has some transmitters that don't use UDP ports and no timeout occurs with these.
I need to discover what is causing the timeout and either increase the interval or preferably disable it completely.