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Re: draft-bourbaki-6man-classless-ipv6-00

Fernando Gont <fgont@si6networks.com> Fri, 09 June 2017 04:19 UTC

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Subject: Re: draft-bourbaki-6man-classless-ipv6-00
To: Lorenzo Colitti <lorenzo@google.com>, Brian E Carpenter <brian.e.carpenter@gmail.com>
Cc: IETF IPv6 Mailing List <ipv6@ietf.org>
References: <20170602141112.x64nleqclygz7dwd@Vurt.local> <20170602141259.GD30896@gir.theapt.org> <CAKD1Yr0DtQYvCYLQexhXe_nhb5rjeyhnB4bCveqyO5Xbuwdg1A@mail.gmail.com> <CAKFn1SEdjhsQ3tKPZdbdfF4ArDzw-FZfjQT68gV55Fc-5vzBvw@mail.gmail.com> <CAKD1Yr3ppM0UF8HoN8PgS7F0iEmK26ebiuJK=tkAdZnuLWpkZg@mail.gmail.com> <CAKFn1SHASt34ihJmGN0iRFQQzLTMspZfxXHgBjBatXXcRYF4cw@mail.gmail.com> <20170604093119.nt733rb3ymmjssww@Vurt.local> <m1dHTLx-0000DcC@stereo.hq.phicoh.net> <CAKD1Yr0ZZwRar6D-2bkXBKPYehqqW99+BMtDOjyovR8WDXKzxw@mail.gmail.com> <CAD6AjGTjikAWutcenW8qn7OW8kPM9c_x_yDUy5vQxJmXKL85dg@mail.gmail.com> <91c3c0f4-eb8b-cdf7-b9c9-7d1eecb7fe64@gmail.com> <CAKD1Yr0_WR_TB+OC0U1Qt2h6WzUp9EGvrqC1ZKW2mwFeBd3bCQ@mail.gmail.com> <4021a559-5b6d-b3fb-19cd-afbe9041e8f2@gmail.com> <CAKD1Yr1wmY3O9Uxe=KRxzCidpyhn3e0zSnikY0K6LK9ue4OzwA@mail.gmail.com> <71c7286c-0e86-5dbe-f9c2-7d473d1de728@gmail.com> <CAKD1Yr3SUOPd+5H66WPc2ikxauVWVG2ZBjFTHoFOQPCEYTBdiA@mail.gmail.com>
From: Fernando Gont <fgont@si6networks.com>
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Date: Fri, 09 Jun 2017 07:19:06 +0300
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On 06/08/2017 02:56 PM, Lorenzo Colitti wrote:
> On Wed, Jun 7, 2017 at 8:24 AM, Brian E Carpenter
> <brian.e.carpenter@gmail.com <mailto:brian.e.carpenter@gmail.com>> wrote:
> 
>     "Interface Identifiers should be 64 bit long except
>     when the addresses are manually configured,
> 
> 
> In order to publish that text we need to agree on what it means. Can you
> explain the semantics of the the interface identifier of a manually
> configured IPv6 address? What are they used for?
> 
> Note: the semantics are *not* the same as the prefix length of an IPv4
> address. The prefix length of an IPv4 address implies that that subnet
> is reachable on, but the IID implies nothing about reachability.

The semantics are exactly the same. An address is an address.

The IID only comes into play when you specify prefixes: when you know
that a given subnet employs a given prefix, the 128-prefix bits are what
differentiate among nodes within such subnet (although such distinction
is not even necessary).

The only reason why we care abut IIDs is because with SLAAC, that's the
part each host has to generate. -- e.g., in a DHCPv6 world you only care
about whole addresses, and prefixes in your routing table.

Thanks,
-- 
Fernando Gont
SI6 Networks
e-mail: fgont@si6networks.com
PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492

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