Subject: A Transition architecture where neither ISP-NATs nor CPE-NAT64s are neeeded

From: Rémi Després <[email-masked]>
Date: Mon, 07 Apr 2008 15:23:03 +0200

The following draft has just been posted.

http://www.ietf.org/internet-drafts/draft-despres-v6ops-apbp-00.txt

It presents an approach whereby:
- The IPv4 to IPv6 transition period needs neither NATs in ISP
infrastructures, nor NAT64s in CPE routers (only NAT44s, plus an
address-port-borrowing-protocol similar to that presented by Brian
Carpenter in SHANTI).
- It also revives and improves the DSTM idea that duly augmented dual
stack hosts can establish pure IPv4 E2E transport connections (more E2E
transparency by augmenting the number of configurations where no NAT at
all is necessary).

Regards.

Rémi

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From: Brian E Carpenter <[email-masked]>
Date: Mon, 14 Apr 2008 10:41:22 +1200

Rémi,

I think this  is a very interesting approach.
We could summarise in two phrases, I think:

1. Tunnel to NAT
2. Borrow Address/Port

However, it doesn't solve the case of a genuine "unistack"
IPv6 host, and we have to decide whether that case is of real
concern.

I was also wondering whether the work in SOFTWIRE already
covers at least part of this solution?

     Brian

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From: Rémi Després <[email-masked]>
Date: Mon, 14 Apr 2008 12:16:49 +0200

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From: Rémi Després <[email-masked]>
Date: Mon, 14 Apr 2008 13:20:13 +0200

Brian E Carpenter wrote :

> I think this  is a very interesting approach. We could summarise in
> two phrases, I think:
> 
> 1. Tunnel to NAT 2. Borrow Address/Port
What about:
- Tunnel to Address/Port server
- NATv4 before tunnel if the client is v4-only

> However, it doesn't solve the case of a genuine "unistack" IPv6 host,
> 
> 
Right.

> and we have to decide whether that case is of real concern.
I agree.
My view on this has changed from "We should do something" to "We can
specify simple enough dual-stack solutions. The need is no longer
clear".

Some may judge however that there is such a need, and may wish to
standardize for this a NAT64, with all its ALG iplications.
At least, their approach should not preclude simpler and more
powerful solutions for more basic transition needs.

> I was also wondering whether the work in SOFTWIRE already covers at
> least part of this solution?

You are right. The draft should probably have discussed it.
- The Softwire solution is however such that dual-stack hosts, or CPE
routers, can borrow *addresses*, NOT *address-port combinations*. This
IMO is a major functional difference (public-IPv4 address space is used
much less efficiently than with NATs or with APBP).
- It imposes that all connections of a client host traverse the same
softwire server (less scalability).
- It implies substantially more complexity in dual stack hosts.

Regards.

Rémi