Re: Objection to draft-ietf-6man-rfc4291bis-07.txt - textual representation of prefixes

Alexandre Petrescu <alexandre.petrescu@gmail.com> Sun, 05 March 2017 12:39 UTC

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Subject: Re: Objection to draft-ietf-6man-rfc4291bis-07.txt - textual representation of prefixes
To: Brian E Carpenter <brian.e.carpenter@gmail.com>
References: <20170223134026.GI5069@gir.theapt.org> <ae35b45a-0398-840f-fc0d-1f64dd2fcc58@gmail.com> <37851ee3-03be-8bee-6190-f4d28df86305@gmail.com> <alpine.DEB.2.02.1703012051590.30226@uplift.swm.pp.se> <b5784622-c24e-a531-4e68-249b03701941@gmail.com> <CAAedzxrSTFe0GgYuvtXPNE=R_ZCXotxL7HbKdj5A4-869rncmw@mail.gmail.com> <ba025be6-709d-87b4-f388-d6f143408277@gmail.com> <alpine.DEB.2.02.1703021029010.30226@uplift.swm.pp.se> <4e17a9f4-6daf-787f-0321-3327fe601d70@gmail.com> <bead3cd8-f7f9-37b3-66f9-e76ae94056d1@baanhofman.nl> <63d98caf-ab70-088f-ff6b-ad27a11619e0@gmail.com> <CAJE_bqcOLSK061p_biSD3GK1y464Ld=8Zp3-hAuJqQ2R2t3JRw@mail.gmail.com> <68803ac3-97f4-838c-ffd2-a294d7fb6d0d@gmail.com> <CAJE_bqc7cFrhCaiGMGeSUf1zMsXpcoDUVvYQ13L-Soe4Rwf6RA@mail.gmail.com> <a630f8b8-e6ed-885a-a909-6c75dfd79892@gmail.com> <49C3F649-FEC9-430E-B716-D5608E00D385@gmail.com> <23d0ed53-918f-dec0-1914-57f2e31bccc9@gmail.com> <401d81b3-f8e5-d38c-826b-167ca6b1f917@gmail.com>
From: Alexandre Petrescu <alexandre.petrescu@gmail.com>
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Date: Sun, 5 Mar 2017 13:39:47 +0100
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Le 04/03/2017 à 20:29, Brian E Carpenter a écrit :
> On 05/03/2017 01:09, Alexandre Petrescu wrote:
>> Fred,
>>
>> I think the problem I have - agreed, on my side - is that
>> "fe80::/10" is sometimes read as a link-local address, other times
>> as a prefix configured on a computer, other times as just the first
>> 10bits of an LL address.
>
> It's a prefix. ("Point, à la ligne.", comme on dit en francais.)
>
> The problem isn't there. It's that in a router, a prefix is the
> thing you perform longest match against. In a host, it's what you use
> in source address selection, next-hop router selection, and on-link
> determination, and during address auto-configuration. So it has many
> roles.

YEs, it has many roles.  An additional role is that of recognising an
address based on its X leading bits.  Even though the prefix of that
address is not only its X leading bits.

This is in itself confusing.

> And fe80::/x is just a special case. No way round that.

...there are so many special cases: fc00 an fd00 meaning the same, the 
::/0, the 1::1/128 meaning an address _and_ a prefix, and so on.

> Also, it's meaningless without an interface, but we don't write
> fe80::/10%eth0.

I think that %iface should be mandatory in notation of LLs.  Otherwise 
there can be collision.

Alex

>
> Brian
>
>