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Re: Access to the IPv4 net for IPv6-only systems, was: Re: WG Action: Conclusion of IP Version 6 (ipv6)

  • From: Iljitsch van Beijnum
  • Date: Mon Oct 01 05:04:27 2007

On 30-sep-2007, at 5:10, John Curran wrote:

The irony is that the I* rationale for moving NAT-PT to historic
was "to restore the end-to-end transparency of the Internet"
and yet the only real chance we have to restore end-to-end
transparency is to first have a transition to the IPv6 (using
dual-stack, NAT-PT, and every other tool at our disposal) and
then over time let present IPv4 destination sites add IPv6 for
end-to-end transparency based on their actual need for it.
Instead, central planning may have effectively killed the very
tool that's needed to allow providers to provision new Internet
customers over a pure IPv6-only model, and create the right
motivation for existing Internet sites to go dual-stack and
actually gain "end to end transparency" via IPv6.

In my opinion, the mistake the IETF made was to "deprecate" NAT-PT without coming up with an alternative first.

Originally, my thinking was "sure, NAT-PT doesn't work with everything unless you have ALGs for a good number of protocols, but it gives you 80% of what you need so it's a good start". But I've come to see how having IPv6 applications expect end-to-end IPv6 connectivity and then have that rug pulled from under them will inevitably lead to the same lack of end-to-end transparency in IPv6 that we currently have with IPv4. And once that can is open, it's unlikely we can get the worms to crawl back inside later.

But proxying can be that 80% solution and tunneling IPv4 over IPv6 can be a 100% solution so we don't have to raise NAT-PT from the dead.