Re: IID length text

Fernando Gont <fgont@si6networks.com> Wed, 18 January 2017 01:42 UTC

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Subject: Re: IID length text
To: sarikaya@ieee.org
References: <148406593094.22166.2894840062954191477.idtracker@ietfa.amsl.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> <fcf580ec-3617-ca5f-5337-37acb6e928ba@gmail.com> <32121fe2-85d5-4849-d77d-edda5825d8e7@gmail.com> <CAC8QAccN_=x9sTgTM71XFSYfUmSyaMHw_tFEw2QSr5iwi2wcGw@mail.gmail.com> <525a97ff-4314-676a-3ee2-7f1fb6c3bf82@si6networks.com> <CAC8QAcebfUyq49HoiG3-dO-VjHs0ztt6J6T4c31foRuSOjzZxQ@mail.gmail.com> <b683564b-a9a0-6596-a6b1-881d71f390f3@si6networks.com> <CAC8QAcfHMPP4HcC+VadXWZpTNZPtD0gixvHy7HDJFDqNF=zyQQ@mail.gmail.com> <bb9f0d2a-d4f7-fb84-1ca8-daf5cb761c08@si6networks.com> <CAC8QAcddXrjHEvLhAwsVKwHks9jQP9eU=6WCy-u7VtdxQ_GJ+Q@mail.gmail.com>
From: Fernando Gont <fgont@si6networks.com>
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On 01/17/2017 06:31 PM, Behcet Sarikaya wrote:
> On Tue, Jan 17, 2017 at 2:55 PM, Fernando Gont <fgont@si6networks.com> wrote:
>> Hello, Behcet,
>>
>> On 01/17/2017 02:39 PM, Behcet Sarikaya wrote:
>>> On Mon, Jan 16, 2017 at 4:09 PM, Fernando Gont <fgont@si6networks.com> wrote:
>>>> On 01/16/2017 06:22 PM, Behcet Sarikaya wrote:
>>>>> On Mon, Jan 16, 2017 at 2:46 PM, Fernando Gont <fgont@si6networks.com> wrote:
>>>>>> On 01/16/2017 05:42 PM, Behcet Sarikaya wrote:
>>>>>>> On Mon, Jan 16, 2017 at 2:27 PM, Alexandre Petrescu
>>>>>>> <alexandru.petrescu@gmail.com> wrote:
>>>>>>>> Le 14/01/2017 à 20:49, Brian E Carpenter a écrit :
>>>>>>>>>
>> [....]
>>>>>>
>>>>>> What does a layer-2 EUI have to do with a layer-3 address?
>>>>>
>>>>> I don't know, you tell me :-)
>>>>
>>>> Answer: Nothing. The fact that we've been embedding layer-2 "addresses"
>>>> into layer-3 addresses should not be taken as a reason for the two of
>>>> them of having to do anything with each other. So, yes, the 64-bit IID
>>>> length is, in reality, arbitrary. They could have been e.g. 32-bits or
>>>> 48-bits (yes, multiples or 64 or 32 tend to be nicer)
>>>>
>>>
>>> I don't think you know much about MAC addresses and its history.
>>
>> I don't know much about elephants, either. Whatever the history (which
>> you imply I don't know), it is irrelevant, because it doesn't change the
>> fact that you don't need to screw your layer-3 protocol with your
>> layer-2 IDs/"addresses".
>>
> 
> Good luck then running SLAAC or ARP :-)

SLAAC: Yes, mac addresses used to be embedded in the IID, That's an
artifact of history, not a design principle. And we're heading towards
replacing that with RFC7217 (which, for many implementations, is already
the case) -- and has always been the case for, e.g., RFC4941.

Neighbor Discovery: NS/NA messages employ link-layer address options,
which essentially convey the link-layer address as an opaque value.
That's used for learning the layer-2 address when sending a packet on a
link, which is a totally different thing from exposing such layer-2
address at layer-3.

There's no reason or requirement that I communicate my layer-2 address
in my layer-3 protocol when, e.g., I connect with a web server. That has
been an artifact of history (which may have happened as such for
multiple (possibly valid) reasons), but please don't confuse that with a
design principle or some sort of law from nature.

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