Re: Updated IID length text

Lorenzo Colitti <lorenzo@google.com> Thu, 19 January 2017 03:04 UTC

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From: Lorenzo Colitti <lorenzo@google.com>
Date: Thu, 19 Jan 2017 12:04:09 +0900
Message-ID: <CAKD1Yr2vmDkUTvSw7-GtKNeMDm1xtAppj+EW9X=-TeKZ6qkXrg@mail.gmail.com>
Subject: Re: Updated IID length text
To: "Manfredi, Albert E" <albert.e.manfredi@boeing.com>
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On Thu, Jan 19, 2017 at 11:46 AM, Manfredi, Albert E <
albert.e.manfredi@boeing.com> wrote:

> Now that we have moved away from using the MAC address for SLAAC, it's not
> clear to me why a host cannot wait for a RA, and then decide on how many
> IID bits to use, based on the prefix length(s) advertised by the router.
>

The reason it can't do that is that in practice SLAAC only works well if
the probability of collision is negligible. Even reducing that from 64 bits
to 48 bits impacts that substantially.