IPv6

IPv6 is needed because IPv4 (the current IP protocol) has run out of room - all the available addresses have been allocated to the various regions, and ISPs are in the process of using them up. While NAT has allowed us to last this long, and to continue stretching it out for a while, IPv6 is a much better solution, and getting it up and running in parallel with IPv4 ("dual stacking") avoids doing under the gun when you *have* to. Granted, that's a long ways out, but the ball is rolling and the sooner everyone supports IPv6, the easier the transition will be. The one thing to watch out for is that with IPv6, you don't have the inherent basic firewall that NAT provides, so you have to make *sure* you are blocking incoming traffic you don't actually want at your firewall.