Subject: [BEHAVE] About Integrating Dual Stack and v4/v6 Translation...

From: Christian Vogt <[email-masked]>
Date: Sun, 16 Nov 2008 09:48:07 -0600

Translation and Dual-Stack Fans,

I was thinking of integrating dual stack and v4/v6 translation in an
effort to get the combined benefits of both interworking techniques.
Since it would be interesting to hear what the people on this list think
about the idea, I will briefly motivate and describe it here:

An advantage of dual stack relative to v4/v6 translation is that it
provides support for both IP versions to applications.  This comes at
the cost of having to provide both IP versions also in the network,
which implies two disadvantages:  (i) A dependency of the host on the
network, and (ii) a source of extra administration costs for the network
operator.  Network support for one IP version can be minimized through
tunneling, as in dual stack lite, but it cannot be eliminated.  Vice
versa, v4/v6 translation reduces the cost of network administration
because it works with a single-stack network, but it requires
applications to support a specific IP version.

The idea now is to perform v4/v6 translation in hosts in cases where the
network does not support the IP version required by an application.
Hosts in addition have a dual stack, so as to avoid v4/v6 translation in
cases where the network does support the IP version required by the
application.  This would provide support for both IP versions to
application, as in dual stack; and it would still work with only one IP
version in the network, as in v4/v6 translation.  We would therefore
combine the advantages of dual stack with the advantages of translation.

Since the above idea seems straightforward and benefitial to me, I
wouldn't be surprised if it had been proposed before.  Apologies in that
case for re-inventing the wheel.

- Christian

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From: "Eric Klein" <[email-masked]>
Date: Mon, 17 Nov 2008 10:22:16 +0200

On Sun, Nov 16, 2008 at 5:48 PM, Christian Vogt <[email-masked]
> wrote:

> Christian,

How is this compared to the dual stack lite draft?
Eric
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From: Christian Vogt <[email-masked]>
Date: Mon, 17 Nov 2008 14:05:45 -0600

> How is this compared to the dual stack lite draft?

Eric,

dual stack lite uses tunneling, whereas the integrated dual-stack/
translator that I am describing uses translation.  Hence, in dual stack
lite, the host depends on a remote tunnel endpoint being provided in the
network (or possible in the peer host).  This dependency does not exist
for an integrated dual-stack/translator.

- Christian

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From: Iljitsch van Beijnum <[email-masked]>
Date: Mon, 17 Nov 2008 14:15:10 -0600

> for an integrated dual-stack/translator.

So this is only for the benefit of applications that don't support the  
IP version that is available, right?

You're not talking about NAT464, or are you?
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From: Brian E Carpenter <[email-masked]>
Date: Tue, 18 Nov 2008 09:28:52 +1300

Christian,

Have you looked at Bump in the Stack (RFC 2767) and
Bump in the API (RFC 3338)?

   Brian

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From: Christian Vogt <[email-masked]>
Date: Mon, 17 Nov 2008 14:35:10 -0600

Iljitsch -

> IP version that is available, right?

It is of benefit for both applications and network operators:  For
applications, because they will continue to work anywhere even if they
support only one IP version.  For network operators, because they don't
break application if they provide only one IP version in their networks.

> You're not talking about NAT464, or are you?

Right; I am not talking about NAT464.

- Christian

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From: Christian Vogt <[email-masked]>
Date: Tue, 25 Nov 2008 14:05:09 +0200

Brian E Carpenter wrote:

> Have you looked at Bump in the Stack (RFC 2767) and Bump in the API
> (RFC 3338)?

Brian -

sorry for the long delay, and thanks for the pointers.  Yes, RFC 3338
describes the type of technique I was having in mind.

However, one thing that surprised me when reading RFC 3338 is that the
document does not explicitly address the scenario where two dual-stack
hosts are connected by only an IPv6 path, and at least one of the hosts
is RFC-3338-capable.  Instead, the document is tailored to the scenario
where an RFC-3338-capable host communicates with a peer that is
IPv6-only.  Clearly, the API translator should be used in both cases.
If the former case is omitted, we rely on the availability of an IPv4
path, so we lose the benefit of enabling IPv6-only networks.

- Christian