Calls intermittently going directly to voicemail

[VOIPoTim]

The translated port number on the public side could be different depending on the router.

The problem is that the majority of new routers don't handle the negotiation correctly and the ports are mixed up. So if the router is not expecting a connection on a given port, it will reject the incoming connection. Some routers do this properly, but it's rare to see it.

In theory users should not need ports forwarded, but again 99% of the time when we see the issues like this in logs, the logs for the user show that the packets were rejected by the router which in turn sent an error code back and it was passed upstream generating a drop to fast busy, disconnected, etc.

So you're correct that in theory, the routers should be able to negotiate. Most new ones rewrite all packets though and don't do it correctly so the ports aren't correct. Since this changes even with router firmwares (and we've learned most new routes auto update themselves), we can't really track which routers handle it properly and which don't (especially since we'd have to track every single firmware version too).

We don't provide networking support and recommend using connect our devices directly to their modems and bypass their consumer router and use the router built into the adapters. When they have issues that are 100% caused by a consumer router, we have to take the most direct approach to resolve the issues for our service. In this situation, it's to forward the entire range since that is effective 100% of the time.

Should users need to do it? No. As long as router manufacturers continue on the path they are on with adding all this unnecessary stuff (like SIP ALG, filtering every single packet and rewriting incorrect, etc), forwarding will eventually be needed by everyone or someone is going to have to invent workarounds.

Here is a perfect example where the stock Linksys router firmware for a brand new router completely breaks VoIP service and the user experienced all the standard router issues commonly caused by a consumer router (things like dropped calls, no audio, disconnected messages, missed calls, etc). Swapping to a firmware that handled it correctly and 100% of the issues were gone.

http://www.dslreports.com/forum/r221...Linksys-router

Router manufacturers are making things more and more difficult every day. Today I actually tell our team that the #1 thing that can make or break a user's VoIP experience is their router. It's no longer the internet connection because nearly all of those are fine for VoIP, but the majority of new routers require tweaking.