Re: IID length text

Brian E Carpenter <brian.e.carpenter@gmail.com> Mon, 16 January 2017 22:23 UTC

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Subject: Re: IID length text
To: sarikaya@ieee.org, Alexandre Petrescu <alexandru.petrescu@gmail.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> <fcf580ec-3617-ca5f-5337-37acb6e928ba@gmail.com> <32121fe2-85d5-4849-d77d-edda5825d8e7@gmail.com> <CAC8QAccN_=x9sTgTM71XFSYfUmSyaMHw_tFEw2QSr5iwi2wcGw@mail.gmail.com>
From: Brian E Carpenter <brian.e.carpenter@gmail.com>
Organization: University of Auckland
Message-ID: <94dffda9-0a88-cfa1-6281-5d788a7ca121@gmail.com>
Date: Tue, 17 Jan 2017 11:23:47 +1300
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On 17/01/2017 09:42, 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.
> I don't think 64 bit limit is that arbitrary?

It's a parameter, which we happened to set initially to 48
and then changed to 64 because of FireWire. I don't know
why 3GPP chose the same value. But indeed we (the IETF) chose
it because of our now old-fashioned decision to copy Novell
Netware by embedding layer 2 addresses in layer 3. A bad
choice, as it turned out.

The first two definitions of "arbitrary" in Merriam-Webster seem
to fit, especially the second.

"existing or coming about seemingly at random or by chance
or as a capricious and unreasonable act of will"
"based on or determined by individual preference or convenience
rather than by necessity or the intrinsic nature of something"

Regards
    Brian

> 
> Behcet
> 
>> Alex
>>
>>>
>>> Regards
>>>    Brian
>>>
>>> --------------------------------------------------------------------
>>> IETF IPv6 working group mailing list
>>> ipv6@ietf.org
>>> Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6
>>> --------------------------------------------------------------------
>>>
>>
>> --------------------------------------------------------------------
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>> ipv6@ietf.org
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>>
> .
>