v4 NAT vs NAT-PT models [Re: 3gpp-analysis: IMS/SIP transition [RE: NAT-PT Applicabilty for 3GPP]]

[Pekka Savola <pekkas@netcore.fi>]

On Tue, 18 Nov 2003, Suresh Satapati wrote:
> > Again, it is not required.  Many NAT boxes do implement this, but many
> > others do not.  IPv4 NAT is fully functional without a DNS ALG.
> >
> > > This has been extended to v6<->v4, where an IPv6 address is being
> > > replaced w/ an IPv4 one.
> >
> > Right, but you cannot implement NAT-PT without DNS-ALG, or something to
> > replace the functionality (whereas with v4 NAT, there is no need for the
> > functionality).
> 
> Just like you can make a v4NAT work, you can make NAT-PT work without
> a DNS-ALG. The model is the same.

I do not know why you insist on that, because it's clearly wrong, or 
you have a lot of assumptions about what you mean with "make NAT-PT 
work".

If I am behind a v4 NAT without DNS-ALG, and I try to connect to 
www.google.com, the connection succeeds and it works.

If I am behind NAT-PT, without DNS-ALG, have v6-only host, and I try 
to connect to www.google.com, the connection fails because the NAT-PT 
cannot find the AAAA record for www.google.com.

These models are NOT the same.

You probably assume some other mechanism for providing similar mapping
than DNS-ALG for NAT-PT.  For example, manual assignment could be OK
for "inbound" services.  But that's completely unspecified.

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings