Re: IID length text

Fernando Gont <fgont@si6networks.com> Mon, 16 January 2017 22:10 UTC

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Subject: Re: IID length text
To: sarikaya@ieee.org
References: <148406593094.22166.2894840062954191477.idtracker@ietfa.amsl.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> <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>
From: Fernando Gont <fgont@si6networks.com>
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Date: Mon, 16 Jan 2017 19:09:52 -0300
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Cc: Alexandre Petrescu <alexandru.petrescu@gmail.com>, 6man <ipv6@ietf.org>
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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 :
>>>>>
>>>>> A modest suggestion:
>>>>>
>>>>> OLD
>>>>>    For all unicast addresses, except those that start with the binary
>>>>>    value 000, Interface IDs are required to be 64 bits long.  Background
>>>>>    on the 64 bit boundary in IPv6 addresses can be found in [RFC7421].
>>>>>
>>>>> NEW
>>>>>    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, consistent use of Stateless Address Autoconfiguration
>>>>>    (SLAAC)[RFC4862] requires that all interfaces on a link use the same
>>>>> length
>>>>>    of Interface ID. In practice, this means that to guarantee
>>>>> interoperability
>>>>>    of SLAAC, a fixed length of Interface ID is necessary. For all
>>>>> currently
>>>>>    allocated unicast addresses, except those that start with the binary
>>>>>    value 000, that length is 64 bits. Note that this value is an arbitrary
>>>>>    choice and might be changed for some future allocation of unicast
>>>>> address
>>>>>    space. Background on the 64 bit boundary in IPv6 addresses can be found
>>>>>    in [RFC7421].
>>>>
>>>>
>>>> I agree with the change suggestion.  The new text and references are enough
>>>> motivation to clarify that that 64bit limit is an arbitrary choice and might
>>>> change in the future.
>>>>
>>>
>>> 3GPP assigns 64 bit prefixes to each UE.
>>> Extended Unique Identifiers defined are EUI-48 and EUI-64.
>>
>> 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)

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