Subject: Re: Stupid NAT tricks and how to stop them.

From: [email-masked] (Noel Chiappa)
Date: Tue, 28 Mar 2006 09:40:44 -0500 (EST)

> From: Keith Moore <[email-masked]>

    > NATs do harm in several different ways 

It's not just NAT's that are a problem on the fronts you mention, though:

    > they block traffic in arbitrary directions

My ISP blocks incoming SMTP and HTTP connections. Has nothing to do with
NAT.

    > these days they often destroy transparency. 

Some ISP's trap outgoing HTTP requests and silently divert them to caches.
Again, it's not just NAT that's doing this.

    > NATs started with a simple design, pretended it would work well
    > without doing the analysis,

Actually, I think the people who started NAT's (mostly Paul T) understood
quite well what the problem were going to be. It's just that NAT was such
a simpler/cheaper solution in the short term that it was too attractive.

Realistically, the last chance to avoid NAT was when variable-length
addresses were removed from IP somewhere in the TCP 2.5 -> TCP 3.0 -> TCP
3.1 transition (I don't know exactly which stage it was). In other words, a
*loooonnnnggg* time ago. We've just been along for the ride ever since.

	Noel

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From: Keith Moore <[email-masked]>
Date: Tue, 28 Mar 2006 13:33:46 -0500

> It's not just NAT's that are a problem on the fronts you mention, though:

yes, there are other things that do harm besides NATs.  
however, that's not a justification for NATs.