It's a very different circumstance that we have today with NAT and it only gets worse as utilization increases.
Does it really get worse? Or do the ISPs with the eyeballs point at their 6to4, Teredo, ALG installations and happy customers with IPv6 access lines? And do the ISPs with the content point at their native IPv6 servers, and 6to4 relays and ALG installations? And do the people making the purchasing decisions cut short the NAT over NAT party before it has barely begun? Let's face it, this is not a technical problem. IPv4 is running out soon. IPv6 does not suffer from this "brick wall" problem and makes future network design/deployment easier to do without contortions. The economic imperative is for companies to go with whatever is simpler in the long run because that is how they recover costs. Spend some capital to build something, rake in recurring fees for a few years, and either profit from it or lose. The capital cost is less important than the operating cost because operating cost eats into margins. Simpler is better when it comes to operating costs. It is true that telcos have, in the past, been able to warp the market economics and get away with very high recurring fees that could cover the high operating costs of complex infrastructure. But does anyone believe this will happen again within the lifetimes of those people who wielded their purchasing power and pushed recurring fees down, down, down? Fact is, that IPv6 is more of a known quantity than IPv4 super NAT with ever longer prefixes and scraping the barrel for reusable IP addresses. And IPv6 is a more constraint-free environment to play in than the IPv4 endgame. If everybody had to play with the same constraints it would be different. But the fact is that some companies have already made the decision to shift their activity to IPv6 along with rising market demand for IPv6. They are hoping to get some of *YOUR* choice customers when contract renewal time comes around because those choice customers are beginning to fear that your company will go bankrupt in 2010/2011 when the demand for IPv6 goes through the roof. Of course it is better for everybody if there are only a few such shortsighted companies because the shift to IPv6 will be enough work without an exponential increase in customers fleeing from other providers. And even an IPv6 network needs peers so it is in everyone's interests that most of us get IPv6 up and running very soon now. --Michael Dillon