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Re: Follow-up work on NAT-PT

On 2007-10-30 02:47, David Miles wrote:

Brian,
In the introduction I'd suggest we add some words to clarify that the scope of v4-to-v6 translation is not broadly "IPv4 to IPv6", but a specific case where a IPv6-only host is modified (with the inclusion of a shim and possibly DNS resolver changes) to allow it to leverage a separate device (the translator) to access the IPv4 Internet. 

Sure, that's the scenario (or possibly "to access a residual fragment
of the IPv4 Internet" at some much later stage).
Also consider the readability of the draft (your intro is very detailed) and adding a section about the placement of the translator? 

Agreed; this is a first cut rapidly transcribed from the whiteboard.
I'm afraid that we need to push the IPv6 component of your proposal much closer to the IPv4 host appreciating the dire situation with globally routable IPv4 addresses. As it stands SHANTI would most likely be deployed with both v6-host and translator in a closed administrative environment, 

I don't think that is required, but it seems likely that a network
wishing to support IPv6-only hosts would choose to deploy SHANTI
translators at its edge. However, the reason that only standard
IPv6 addresses are used is so that there are no topological
restrictions on where the translators are placed.
but I'd like to consider the bigger challenge of these v6-only hosts communicating with v4-only hosts over a IPv6 Internet (rather than an IPv4 one). I'm not sure you were trying to take on something that big, but I thought I'd shoot the question through. 

Well, in that case your translator, however it works, has to be
close to the fragment of IPv4 that the v4-only host is attached
to. That will apply even if the fragment is a single PPP link.
I wouldn't recommend SHANTI for that, probably.
I'm interested to hear your thoughts on IPv6-only hosts (as opposed to dual-stack hosts) during the IPv4-to-IPv6 transition period. The work I've been doing up till now has made a fundamental assumption that we would see only v4-only and dual-stack hosts, assuming that only post IPv4 shutdown would we see an emergence of IPv6-only devices. 

The IAB request specifically asks for a solution for IPv6-only
hosts. It's long been my view that the primary coexistence strategy
must be dual-stack, but I'm trying to answer the IAB's question.
Finally, from my reading the usefulness of SHANTI is only where the IPv6-only host has an application that appreciates IPv4 parameters (port and address) or the translation itself. Do we expect application developers to widely cater for this scenario, or to make the assumption that "if IPv4 matters we should use the IPv4 stack"? 

No, SHANTI will work out of the box for any application that runs
through a traditional NAT or NAPT without problems *and* has been
upgraded to AF_INET6 sockets. However, applications that require
an ALG with traditional NA(P)T will need to be tweaked, I think.
The question is whether that overhead is justified to get rid of
the problems of NAT-PT?

    Brian


Best Regards,

-David Miles

On 29/10/2007, at 10:48 AM, Brian E Carpenter wrote:


On 2007-10-14 06:28, Jari Arkko wrote:

Thanks for this, Olaf. Indeed, we are considering follow-up work,
and understanding the scenarios & possible need for producing
a revised version of NAT-PT is on the Vancouver agenda (currently
planned to be a discussion in V6OPS, with protocol work to fall
out to an INT area WG).


I realise this may be jumping the gun a bit, but since I won't be
in Vancouver, here is a sketch of one possible direction.

   Brian

-------- Original Message --------
Subject: I-D Action:draft-carpenter-shanti-00.txt
Date: Sun, 28 Oct 2007 18:20:01 -0400
From: Internet-Drafts@ietf.org
Reply-To: internet-drafts@ietf.org
To: i-d-announce@ietf.org
A New Internet-Draft is available from the on-line Internet-Drafts directories.
Title : Shimmed IPv4/IPv6 Address Network Translation Interface (SHANTI) 
    Author(s)       : B. Carpenter
    Filename        : draft-carpenter-shanti-00.txt
    Pages           : 12
    Date            : 2007-10-28

There is a pragmatic need for a packet-level translation mechanism
between IPv4 and IPv6, for scenarios where no other mode of IPv4 to
IPv6 interworking is possible.  The mechanism defined here uses a
shim in both the translator and the IPv6 host to mitigate the
problems introduced by stateless translation.

A URL for this Internet-Draft is:
http://www.ietf.org/internet-drafts/draft-carpenter-shanti-00.txt