> From: Eric Rescorla <ekr(_at_)rtfm(_dot_)com>
> (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.
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
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