Eric Rescorla writes: > I said I was done with this discussion, but I think Melinda > deserves a response here. > > Melinda Shore <mshore@cisco.com> writes: > > > > I'm not sure what you mean by routing above. Are you suggesting there's > > > some negative externality in that NAT makes the routing infrastructure > > > more complicated? If so, what is it? > > > > If you're multihomed and your route changes, your address > > changes. (Yes, this happens). > Agreed. > > > I am profoundly weirded out by reading an IAB member argue > > that something that's got broad market acceptance is > > tautologically okay. I agree that there's a real problem > > here that NAT is trying to solve, but I certainly wouldn't > > treat it as a given that NAT is the best, or even a good, > > solution. > I can understand how this would bother you, and I think > part of the problem is that I haven't been writing as clearly > as I could have. A series of e-mail replies isn't a good > way to elucidate your position. > > Here's what I mean to be arguing: > > (1) There are some set of problems that users have or > believe they have. > > (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. (Here's > where the invocation of revealed preference comes in). > > (4) It may well be the case that some other solution S > would have some other costs Cs and benefit Bs such > that (Bs - Cs) > (Bn - Cn). It may be that S doesn't > exist yet, in which case it would be good for us > to design and build it. > > (5) It's also possible that at some time in the future > Cn will exceed Bn, in which case I would expect people > to stop using NAT and (probably) demand something else. > > (6) The argument that I thought I heard people (though not > you) making is that Cn > Bn. I don't think that this > is likely to be the case. In that sense, I think > NAT is OK. I think that if we believe this, it will likely > lead to us designing a long series of S'es that are > inferior to NAT (in the sense that users do not > prefer them because (Bs - Cs) < (Bn - Cn). That's a waste > of time. > > Does this seem like a weird position for an IAB member to take? > I don't think so. The problem here is that your cost functions are averages when what is far more interesting are the trends. Voice is one trend and it pretty fundamentally challenges one of the base assumptions of NAT: private-client/public-server. But instead of realizing that NAT is architecturally incapable of dealing with private servers and switching back to the model that does accommodate that model fine, we're being driven as a community to do both with the ensuing insanity of two broken models being forced to cohabitate, all the while neither meeting the actual requirements. So just saying that NAT is here get used to it is, architecturally, not helpful. The split of effort is to put it mildly a huge drain on engineering talent, but more importantly the net is becoming more and more incomprehensible because of it, both intellectually as well as operationally. That strikes me as a profound architectural issue, one that should scare anybody who cares about the net. So yes, to my mind saying "get used to it" is a weird position because it discounts the problems of the status quo and doesn't really express any vision for what the architecture *ought* to be, or drive us in a direction which will make that determination possible. What NAT's are telling us is that there are requirements that aren't being met with the current Internet. But that's really the only thing they should be telling us because we already know that NAT's fail miserably on other requirements. We want an architecture that meets all of the requirements, not a hodgepodge of half solutions which fall over in the first stiff breeze.