I've made good progress toward launching my VOIP service to customers of my ISP. I currently have my ATAs on internal IPs with the gateway router doing 1:1 NAT to static public IPs for each ATA. This is working well and I think should eliminate NAT traversal problems.

I did encounter one thing I wanted advice on. During my testing I was having problems with incoming calls ringing but no audio coming through. Packet sniffing I could see the inbound UDP audio stream but the ATA was sending icmp pings rather than audio which were not being returned by the voipo server. After a long time (1 hour +), the condition would correct and calls would work fine. I noticed that this happened only after the ATA was reset. Also noticed that in the voipo cpanel under connections, two connections from the same ATA would show up with different times when this problem occurred. After some time, it seemed like the earlier connection would go away and then the calls would work normally.

I found a setting in the ATA for "Unregister on Reboot" which I set to yes and it seems to have fixed this. The duplicate connections do not appear and calls are working fine immeadiately after rebooting the ATA. I am concerned however that if the ATA loses power or net connectivity rather than being rebooted through the web UI, could the unregistration not go through and cause this condition to appear?

Also, is this timeout window I was seeing related to the "Registration Expiration" setting in the ATA? Right now it's set to the default of 1 hour. Should I make this shorter, like 1 minute?