But why bother modifying every application to try and work through NAT? Might as well invest that time once making it work with IPv6 - since this is going to be essential. The question of IPv6 is not if, but when it will be deployed everywhere. Remember, the consensus is that IPv4 exhaustion will occur within 3 to 7 years, and at that point in time if applications have not been modified to work with IPv6 they will not be usable by new customers. NAT is not the solution to solve IPv4 exhaustion. NAT merely extended the day it was going to run out. NAT was meant to be nothing more than a stop gap measure. -----Original Message----- From: Perry Lorier [mailto:perry(a)coders.net] ... This is becoming less true as every protocol under the sun tries to deal with "breaking through" NAT. Programs need to talk to someone that's not behind NAT to provide a temporary port forward. These machines they talk to are now high value targets as they contain lists of large numbers of computers that are running a particular piece of software and a way to connect back to them even through a connection tracking firewall or NAT box. ...