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Re: Question about RFC6724

Brian E Carpenter <brian.e.carpenter@gmail.com> Mon, 02 May 2022 20:49 UTC

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Subject: Re: Question about RFC6724
To: Philip Homburg <pch-ipv6-ietf-8@u-1.phicoh.com>, ipv6@ietf.org
References: <m1nlQqC-0000IEC@stereo.hq.phicoh.net>
From: Brian E Carpenter <brian.e.carpenter@gmail.com>
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Date: Tue, 03 May 2022 08:49:25 +1200
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On 02-May-22 19:51, Philip Homburg wrote:
>> Excuse my ignorance, but I have a question about RFC6724. The rules depend on
>> longest prefix matching and therefore on the definition of CommonPrefixLen(S,
>> D).
>>
>> The way it's defined doesn't work for ::ffff:0:0/96, as far as I can see:
> 
> In the context of RFC 6724, can you give an example where limiting the
> CommonPrefixLen to 64 gives the wrong result?

If read that way, it means that all IPv4-mapped addresses match each other
at /64. I'm sure that isn't the intention and I very much doubt that any
implementation does that. See my reply to Fred Templin.

> If there is a choice between different IPv4 source or destination
> addresses, then the RFC allows implementations to have extra code.
> Aditionally, specifying the behavior of IPv4 implementations seems
> out of scope.

It's certainly not out of scope for the IETF ("make the Internet work
better") and this RFC was produced by 6MAN.

Regards
     Brian

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