Subject: [BEHAVE] Comments on draft-xu-behave-ivit-00

From: Dave Thaler <[email-masked]>
Date: Thu, 23 Jul 2009 00:19:53 +0000

I read this document and must admit I didn't understand it. :(

What I understood is that it seems to basically say you can
combine translation + encapsulation in the same  box, which is
what I believe the Dual-Stack Lite etc folks already say.

Attached is a marked up copy with my comments (mostly
illustrating my confusion).

-Dave

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From: Dave Thaler <[email-masked]>
Date: Thu, 23 Jul 2009 18:14:51 +0000

Mingwei Xu wrote:
> In host mode, an IPv6 host wants to communicate with a dual stack
> host in an IPv4 network. Yes, you are right. In this scenario,
> there need not translation, some tunnel mechanism can meet the
> requirement. However, in tunnel mechanisms, tunnel end point, e.g.
> a gateway between IPv4 and IPv6 networks, has to maintain a big
> tunnel mapping table if there are many dual stack hosts.

That's not true in general.  ISATAP and 6to4 are two examples
of tunneling protocols where the endpoints are stateless.
If you put a NAT64 on the same box as an ISATAP router,
the tunneling portion is still stateless and the NAT64 is
of course stateful but it is oblivious to the fact that there's
any tunneling.

> While,
> in IVIT, since IPv4 addresses are embeded in IPv6 addresses, the
> gateway can obtain the IPv4 addresses from IPv6 addresses without
> looking up the tunnel mapping table.

I still don't follow what scenario we're talking about.
If the host is IPv6-only it can't do tunneling.  If it can do
tunneling then it's IPv4-capable and you can just use IPv4,
right?

-Dave