It isn't that simple. The fact that NAT exists and is seen as useful by many people (whether or not they are even aware of it) means services and applications need to be aware of it.
This is a hidden cost of NAT. Why hack many applications to work around a network layer problem ?
The best place to fix a problem is where it actually exists. The problem NAT tries to solve, but doesn't solve very well (see the earlier list), exists in the network layer. IPv6 fixes the network layer problem that IPv4 has, and it fixes it better than NAT does. IPv6 isn't perfect, but nothing ever is.
I think that you've misidentified where the problem really exists. I'd suggest that it exists at a higher layer. If I'm a resi broadband subscriber, and I buy an "Internet connection thingamajigger", I may want to hook up more than the one device I'm allowed, in a hypothetical IPv4- only world that works like the one we currently have. And yes, while SOME ISP's do allow you to obtain additional IP addresses, it is certainly not common, nor is it without a monthly cost. Smart end users WILL identify that things like "Internet Connection Sharing" or a NAT gateway will eliminate this cost. So, one of the real problems is that ISP's sell connections "for a single device" to end users. Another problem could be that these are dynamic IP, which makes ever less sense given the nature of always-on Internet access, and the increasing plethora of Internet-capable devices one finds in a home. I realize that these things have typically been differentiators in the service offerings of an ISP, but if you really want to be able to get rid of NAT and truly "go IPv6 native", you're going to have to get rid of the incentives to put a NAT device in, and give end users blocks of address space sufficient to the task. Most proponents of IPv6 seem to be operating under the assumption that an ISP will hand out a block (the latest I recall seeing is RFC 4779, which suggests a /64, IIRC). That would appear to be sufficient to the task, certainly. However, I am left wondering what is going to happen in the event that you're dealing with a service provider who really wants to spec out that a single client is allowed to attach? Because there's a loose correlation between the number of clients behind a connection and actual utilization, carriers have an incentive to limit this... To really encourage the avoidance of NAT, we really need to move to service models where Internet connection sharing is expected and allowed. Limited to within a household? Not technically possible, of course, but you can certainly /write/ such a restriction into the contract. ... JG -- Joe Greco - sol.net Network Services - Milwaukee, WI - http://www.sol.net "We call it the 'one bite at the apple' rule. Give me one chance [and] then I won't contact you again." - Direct Marketing Ass'n position on e-mail spam(CNN) With 24 million small businesses in the US alone, that's way too many apples.