Re: IPv10.

Brian E Carpenter <> Fri, 11 November 2016 22:45 UTC

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Subject: Re: IPv10.
To: Emily Shepherd <>, Khaled Omar <>
References: <> <20161111145124.rqqecqquea7ckj7s@emily-tablet>
From: Brian E Carpenter <>
Organization: University of Auckland
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Date: Sat, 12 Nov 2016 11:45:29 +1300
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On 12/11/2016 03:51, Emily Shepherd wrote:
> On Fri, Nov 11, 2016 at 01:38:34PM +0000, Khaled Omar wrote:
>> You can find the latest version of the IPv10 draft attached in this e-mail.
> This looks fairly similar to just using a IPv4-mapped IPv6 address 
> within an IPv6 packet [RFC4038]; is there a nuance I'm missing here?

Not a big one. Using version number 10 isn't necessary; these could
be standard IPv6 packets. But of course it doesn't solve the basic problem
that makes dual-stack or a middlebox of some kind essential: an unmodified
IPv4 host can't talk to an IPv6 host, or an IPv10 host, because it doesn't
understand the new packet format. So this solution does nothing for backwards
compatibility, unfortunately.

There is a nuance, but a minor one. In the addressing architecture,
"IPv4-mapped" address are under the prefix 0:0:0:0:0:ffff::/96
and are used *internally* in a dual stack host to allow an IPv6
application to use the IPv6 (INET6) socket API to talk to a remote
IPv4 host *via IPv4*.

The deprecated "IPv4-compatible" addresses were under ::/96, which
is the format used in this IPv10 document.

Before we deprecated this, it was all described in RFC 2893 at Unfortunately it
didn't help much, for the reason above.

So Khaled - the good news is that basically you reinvented an idea that
was part of the orginal transition plan for IPv6. The bad news is that we
found out some years ago that it doesn't really help, so we dropped it.

The worse news, slightly embarrassing for me as it happens, is that
RFC 4213 explains that IPv4-compatible addresses were deprecated
in favour of "a much more general mechanism ...specified in RFC 3056"
which has also been largely deprecated due the problems it caused (RFC 7526).

The actual deprecation was discussed at IETF 62 in March 2005 and confirmed
on the IPv6 WG mailing list during that month. The most recent discussion of
the topic that I found is at

    Brian Carpenter

> Emily
> [RFC4038] Shin, M-K., Ed., Hong, Y-G., Hagino, J., Savola, P., and
>           E. Castro, "Application Aspects of IPv6 Transition",
>           RFC 4038, DOI 10.17487/RFC4038, March 2005,
>           <>.
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