> From: Eric Rescorla <[EMAIL PROTECTED]> > (2) NAT solves at least some of those problems, at some > cost (say Cn), both financial and operational and > that solution has benefit Bn.
> (3) The fact that a large number of people have chosen > to use NAT is a strong argument that B>C. Ah, I think your model has a fatal oversimplification here - but it's one I'm glad you made, since it has given me a clue to a deeper understanding of why NAT's are doing so well. Here goes... The problem with your analysis is that there's no single value of C and B for everyone; those numbers depend on what you're trying to do. So for *some* people, B>C (we'll call this group NAT-Users, or N-U for short) - but for *other* people, C>B (and we'll call them NAT-Avoiders, or N-A). We've heard from a number of the latter group - people who want to run voice (not over tunnels), people who want to run IPSEC (not over tunnels), etc. However... The interesting point that I get from thinking about this is that we need to think about the size of the two groups - and in particular, how large the N-U group is likely to be down the line. That group has no reason to deploy any new technology - what they have already works fine for them. So if there is a very large population of N-U, especially if they are a big enough group to be a majority of the Internet user base, then I think we're going to have to continue to interoperate with those people. That means that i) NAT+v4 is here to stay, permanently, as the packet-forwarding substrate on which we have to live, and ii) many "solutions" to the "NAT problem" have a badly faulty key premise - which is that the solution will fix IPv4's problems by replacing it. The notion of a system with a single, globally unique namespace at the lowest level is a really nice one, one we had for a while - and *one we think we can reclaim*. I now think we've been deluding ourselves; that past (like so many others, e.g. the one where we didn't have spam) is gone for good. I think the IETF needs to face that painful reality, or become increasingly irrelevant. Noel