Subject: RE: (ngtrans) NAT-PT DNS ALG issues

From: "Christian Huitema" <[email-masked]>
Date: Fri, 22 Feb 2002 11:45:19 -0800

> note also that there are other areas that require a  translation
> mechanism to operate in IPv4 only, dual stack and IPv6 only mode.
> DNS is a case (see draft-ietf-ngtransdns-ops-req-03),  SMTP is
another...
> As one day itojun pointed out, it would be nice if we could rely on a
> generic translation mechanism for all those applications.

The DNS and SMTP transitions both become much simpler if we can assume
that every IPv6 node can do an UDP transaction or set a TCP connection
to an arbitrary IPv4 node -- what I would call "one way" access to IPv4.
NAT-PT is an easy to implement solution to this problem, IF it is made
simple to use and configure:

* an IPv6 only host that want to access a DNS record from an IPv4 only
server can access it through NAT-PT (if indeed NAT-PT remains
transparent);

* an IPv6 only hosts that want to forward mail to an IPv4 only domain
can set up a TCP connection to that domain through NAT-PT.

Indeed, there is the little detail of providing access from IPv4 to the
DNS records of an IPv6 only domain, or of sending mail from IPv4 to an
IPv6 only domain. For that, we have to use application proxies. The good
part is that in both the DNS and SMTP case, we can use DNS records to
document these proxies: a secondary server that has IPv4 capability and
can forward the request to IPv6; a mail relay that has IPv4 capability
and can forward the mail over IPv6. 

The "green field" network provider that you hypothesize would have to
compare the respective costs of maintaining a dual infrastructure versus
having a pure IPv6 infrastructure complemented by a set of mail and DNS
relays, as well as NAPT servers. If we do a good job of defining the
transition tools, many will choose the IPv6 path. I believe that the key
here is the ease of configuration + the attention to operation issues.

-- Christian Huitema

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From: Keith Moore <[email-masked]>
Date: Fri, 22 Feb 2002 16:05:44 -0500

> I believe that the key

I believe that the key issue is the harm to IPv6 applications if
transition mechanisms like NAT-PT are invisible to applications.

Keith