If you have a Firebrick router, for example, why does one (possibly) need to use your Firebrick as a VoIP gateway ? Or is this not necessary? I wonder if this function is needed by those people who suffer from NAT, is that correct ? And since I don’t use NAT at all, I just have a hole in my firewall open towards my ISP, AA’s VoIP server and let traffic from there come in straight to my Siemens N300IP VoIP box. Is that a valid approach?