Re: on NAT-PT

[Keith Moore <moore@cs.utk.edu>]

> >       it looks that you mean something else, like avoiding the use of
> >       DNS-ALG from NAT-PT (= alter NAT-PT spec).  i don't see real
> >       technical ground for that.
> 
> There is some ground: the possibility to use NAT-PT when the remote
> address is learned outside of the DNS channel.

more generally, the possibility to selectively enable NAT-PT for specific 
services while leaving it disabled for others, regardless of how the 
application learns which address(es) to use.

e.g. to support IPv6 access to a domain's v4-only SMTP servers I would 
like to be able to set up MX records for that domain that point to DNS 
names that resolve to v6 addresses of NAT-PT boxes that will forward
the SMTP traffic to the v4-only SMTP servers.  the primary MX records 
can point to v4 addresses, secondary MX records can point to NAT-PT 
boxes.  that way the mail will be accepted even from v6-only clients.

similar techniques can be used with SRV records, or with other protocols
that do referrals.

what I do not want is to have those NAT-PT boxes try to intercept all
traffic to a particular domain, because this will break some apps.
I'd much rather be able to specify handling on a per-port or per-service
basis, even if that means returning 'connection refused' for some ports.