Subject: NAT-PT Applicability

From: Suresh K Satapati <[email-masked]>
Date: Wed, 22 Oct 2003 02:03:56 -0700 (PDT)

Comments are welcome !!!

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A New Internet-Draft is available from the on-line Internet-Drafts
directories.

        Title           : NAT-PT Applicability
        Author(s)       : S. Satapati, et. al.
        Filename        : draft-satapati-v6ops-natpt-applicability-00.txt
        Pages           : 17
        Date            : 2003-10-20

This document discusses the applicability RFC 2766, Network Address
Translation - Protocol Translation (NAT-PT) employing the Stateless
IP/ICMP Translation (SIIT) algorithm, as an IPv4-to-IPv6 transition
and co-existence mechanism. It highlights the NAT-PT/SIIT operational
principles and the network context for which NAT-PT was designed.
Known limitations of NAT-PT/SIIT are presented. Applicable scenarios

A URL for this Internet-Draft is:
http://www.ietf.org/internet-drafts/draft-satapati-v6ops-natpt-applicability-00.txt

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Sk

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From: "Christian Strauf (JOIN)" <[email-masked]>
Date: Wed, 22 Oct 2003 13:27:31 +0200

> Comments are welcome !!!
Here are my comments.

Para 3.2:
        If more than one box implementing NAT-PT is present, then the
        scalability problem may be circumvented by using e.g. DNS-ALGs
        that can do round-robin or some other form of load-balancing.
        
        Load-balancing also has its drawbacks as the majority of hosts
        cache answers to DNS queries. And additionally, if the NAT-PT
        box and the DNS-ALG are not one unit, failures of one or the
        other are diffcult to handle (due to the current lack of some
        form of communication/surveillance between the two).

It is probably worth to mention that it is to some extent possible to do
load-balancing. Apart from that, I think that the draft is very nice and
surely a good help to get an overview of what problems one can expect
when deploying NAT-PT.

Load balancing NAT-PT is quite a challenge. When using NAT-PT+DNS-ALG to
help IPv6 hosts to connect to the IPv4 world it is more complicated than
simply using a balancing DNS-ALG. It will work nicely until a NAT-PT box
dies or can't handle the amount of traffic anymore. When this is the
case, there have to be some means of notifying the DNS-ALG that this
NAT-PT box is unavailable and has to be left out when assigning IPv6
prefixes to converted IPv4 addresses (assuming that each NAT-PT box
handles the translation for one of those assigned IPv6 prefixes for
converted IPv4 addresses). The question is how this can be done
efficiently. Does the DNS-ALG have to check the NAT-PT boxes somehow? Do
the NAT-PT boxes have to send out notifications that they can't
translate traffic anymore (if there is only a partial failure like too
much traffic/too much CPU usage/...)? Just a thought.

Christian
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JOIN - IP Version 6 in the WiN  Christian Strauf
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From: [email-masked] (Jun-ichiro itojun Hagino)
Date: Thu, 23 Oct 2003 14:59:40 +0900 (JST)

> much traffic/too much CPU usage/...)? Just a thought.

	with a commercial implementation (from Yokogawa) DNS-ALG monitors
	live/dead status of NAT-PT box by some means (ping?) and returns
	fabricated AAAA response with NAT-PT prefix associated with live boxes.
	i don't think we need to go into such implementation details in this
	document.

itojun