Re: Updated IID length text

Lorenzo Colitti <lorenzo@google.com> Fri, 20 January 2017 04:39 UTC

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From: Lorenzo Colitti <lorenzo@google.com>
Date: Fri, 20 Jan 2017 13:38:55 +0900
Message-ID: <CAKD1Yr1no52iZ2NwfKse6tXi0QpOP+Qe-vU68M4g1ZhmsgQadg@mail.gmail.com>
Subject: Re: Updated IID length text
To: Brian E Carpenter <brian.e.carpenter@gmail.com>
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On Fri, Jan 20, 2017 at 4:41 AM, Brian E Carpenter <
brian.e.carpenter@gmail.com> wrote:

> However, correct use of Stateless Address Autoconfiguration
>    (SLAAC)[RFC4862] requires all interfaces on a link to use the same
> length
>    of Interface ID. Furthermore, to guarantee robust interoperability of
> SLAAC,
>    a consistent length of Interface ID is desirable. For this reason,


I object to the text "for this reason", because SLAAC is not the only
reason. There are many reasons, many of which are written in 7421, and two
sentences in this paragraph are not sufficient to describe them. I propose
the following alternative, which I believe to be normatively identical:

   IPv6 routing is based on prefixes of any valid length up to 128 [BCP198].
   For example, [RFC6164] standardises 127 bit prefixes on point-to-point
   links. However, the Interface ID of all currently allocated unicast
addresses,
   except those that start with the binary value 000, is required to be 64
bits
   long. The rationale for the 64 bit boundary in IPv6 addresses can be
found in
   [RFC7421].

Cheers,
Lorenzo