Re: Objection to draft-ietf-6man-rfc4291bis-07.txt

Lorenzo Colitti <lorenzo@google.com> Thu, 02 March 2017 14:03 UTC

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From: Lorenzo Colitti <lorenzo@google.com>
Date: Thu, 2 Mar 2017 23:02:34 +0900
Message-ID: <CAKD1Yr1cNihxMVHjY2j7mcCNU2TE0X6-0p2mDNCBVVUcUbU20Q@mail.gmail.com>
Subject: Re: Objection to draft-ietf-6man-rfc4291bis-07.txt
To: Tore Anderson <tore@fud.no>
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On Thu, Mar 2, 2017 at 8:11 PM, Tore Anderson <tore@fud.no>; wrote:

> > So really, you can't express this type of configuration using only an
> > IPv6 address and a prefix length, because they don't provide enough
> > information to do that. "2001:db8:0:c0:2:100::/80" by itself is not
> > enough: you need one more piece of information, which is the length
> > of the NAT64 prefix.
>
> I'm not exactly sure what you're saying here? RFC7915 does currently
> work, and hosts participating in a network using RFC7915 do not need to
> know the length of the translation prefix.
>

Oh, I see. It works if you ensure that all the hosts and translators agree
on how to calculate the suffix, and no two hosts have IPv6 addresses that
differ only in the suffix. IPv6 addresses that don't have this property
experience unidirectional connectivity to IPv4, and can cause packets to be
sent by third parties to the host that has the correct suffix. Fair enough.


> > As I said before, I think we should have an exception for IPv6
> > addresses where the only non-zero bits in the IID are an IPv4
> > address. Those aren't really IPv6 addresses anyway, they're just
> > convenient representations for IPv4 addresses.
>
> Well, the point is that in order to ensure compatibility with SIIT such
> an «exception» would need to _always_ apply, and then it's not really
> much of an exception anymore.
>

How about an exception for IPv6-translatable addresses, then? I don't think
it's essential that the host know that the addresses are IPv6-translatable.