[arin-ppml] Why are ISPs allowed?

[michael.dillon at bt.com]

> Basically there are a lot of protocols that have been kludged 
> to support one layer of NAT at the edge of the enterprise or 
> home network, but if you add another layer of NAT somewhere 
> things get really squirrelly, really fast.  Also, from a more 
> philosophical standpoint, I'm opposed to any furthering of 
> "oh, they're just consumers; a bit of web surfing, a bit of 
> e-mail, a bunch of the video pap we want to sell them...what 
> on earth would they need to do anything more for?" mindset 
> that already
> taints many consumer offerings.   Let's keep the Internet a 2-way
> medium.  ;-)

The biggest problem is not the NAT (Network Address Translation), 
it is the extension of the network address space by using port
numbers as well. Pure one-to-one NAT is less of a problem.

> Hasn't this topic been beaten to death in many slightly more 
> pertinent venues?

Not only that, but some of those venues have developed NPAT and
NAT64 to allow the use of NAT to be reduced to only enable access
of those sites which have not yet switched to IPv6. This kind of
NAT is far less of a problem than v4 NAT and double NAT. Basically
if you are going to the trouble and expense of using NAT as a 
hedge against IPv4 exhaustion, you get more bang for the buck
with NPAT and/or NAT64.

--Michael Dillon