Re: Updated IID length text

Fernando Gont <fgont@si6networks.com> Thu, 19 January 2017 03:52 UTC

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Subject: Re: Updated IID length text
To: Lorenzo Colitti <lorenzo@google.com>, "Manfredi, Albert E" <albert.e.manfredi@boeing.com>
References: <148406593094.22166.2894840062954191477.idtracker@ietfa.amsl.com> <m2fukqbbwv.wl-randy@psg.com> <F6953234-3F85-4E28-9861-433ADD01A490@gmail.com> <m2wpdzhncn.wl-randy@psg.com> <82245ef2-cd34-9bd6-c04e-f262e285f983@gmail.com> <m2d1frhjfn.wl-randy@psg.com> <18e6e13c-e605-48ff-4906-2d5531624d64@gmail.com> <CAKD1Yr1cvZ8Y3+bHeML=Xwqr+YgDspZGnZi=jqQj4qe2kMc4zw@mail.gmail.com> <m2lguffnco.wl-randy@psg.com> <CAKD1Yr1TrTiPRdyutobmb_77XJ7guNzLrg=H_p7qi4BfQ8V=GA@mail.gmail.com> <m2d1frfm6m.wl-randy@psg.com> <CAKD1Yr2Njjd8_Mr+6TRFF6C5pdcX4yFgpFVyEkykDuytu2B8mg@mail.gmail.com> <2A5073777007277764473D78@PSB> <4596c3d4-a337-f08e-7909-f14270b7085f@gmail.com> <CAN-Dau06R3iYRpYLADhvHox4C9qdsJCuxFsJapRhOQcWT4qk_g@mail.gmail.com> <CAO42Z2weZcoHiBzN94QAQ9WGhWR16PmMMFNg=5YLmr_dhPjjpA@mail.gmail.com> <fcc7f136-b5da-527e-b495-5a2d7f7a3ce8@gmail.com> <55bb8bdbfbf4439da0aa702e5bc03e2c@XCH15-06-11.nw.nos.boeing.com> <CAKD1Yr2vmDkUTvSw7-GtKNeMDm1xtAppj+EW9X=-TeKZ6qkXrg@mail.gmail.com>
From: Fernando Gont <fgont@si6networks.com>
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On 01/19/2017 12:04 AM, Lorenzo Colitti wrote:
> On Thu, Jan 19, 2017 at 11:46 AM, Manfredi, Albert E
> <albert.e.manfredi@boeing.com <mailto: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.

Oh, I love this. So you are a fan of still doing modified EUI-64 with
randomized MAC addresses (which wastes 18 bits, including the 16 bits
that are wasted with embedding 0xfffe), and now you say that using /48
would impact things substantially?

This can't possibly make sense.

If you do /48 + RFC7217, you get even two ore bits of entropy than if
you do Modified EUI-64 with random MAC addresses (a flowed scheme that
you've been fighting for for a while now)

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