I haven't dug too deep into NAT-PT, but an obvious question comes to mind: Why would an ISP deliver an IPv6-only connection plus NAT-PT (and all the likely problems) with a surcharge for IPv4 instead of delivering RFC1918 IPv4 + NAT with a surcharge for routable IPv4?
Why is it an either/or situation? Given the fact that PC's have supported IPv6 for quite a while now, an IPv6 Internet access service is workable, *IF* an ISP can support something that allows the IPv6 user to get to the IPv4 Internet. That is a transition product that will reduce the requirement for IPv4 addresses at the same time as it enables the ISP to market themselves as "Ready for the Future" or whatever. Obviously, the ISP can offer the same old IPv4 service with potentially, double NAT but then they are just making do until some future point in time when they have to deal with IPv6. At that point in time, they may need to offer the NAT-PT solution which means they need to learn about it, do some trials, etc. I'm not suggesting that people should rush out and make dumb business decisions to offer IPv6 services today. I *AM* suggesting that people need to start educating themselves on the intricacies of IPv6, trialing IPv6 in a lab environment, and planning how they will introduce IPv6 services WHEN IT MAKES BUSINESS SENSE TO DO SO. IPv4 exhaustion is close enough that people can't afford to keep their heads in the sand any longer. --Michael Dillon