Re: IID length text

Lorenzo Colitti <lorenzo@google.com> Tue, 17 January 2017 01:44 UTC

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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> <94dffda9-0a88-cfa1-6281-5d788a7ca121@gmail.com> <CAKD1Yr1QTbLsbzxwy4-MCWeAxr0rRvDe5v-6DbA9aYaK48BaZw@mail.gmail.com> <eec38f90-3751-6f74-12a0-321c3dce163a@gmail.com>
From: Lorenzo Colitti <lorenzo@google.com>
Date: Tue, 17 Jan 2017 10:44:00 +0900
Message-ID: <CAKD1Yr18QWOR3_jFHEQ2M0jhgkOwxhbm+SFK3jZF6XU3WtWVGQ@mail.gmail.com>
Subject: Re: IID length text
To: Brian E Carpenter <brian.e.carpenter@gmail.com>
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Cc: 6man <ipv6@ietf.org>, Alexandre Petrescu <alexandru.petrescu@gmail.com>
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But your text does change this arbitrary choice, by removing it.

On Tue, Jan 17, 2017 at 10:36 AM, Brian E Carpenter <
brian.e.carpenter@gmail.com> wrote:

> Nobody is saying we should change it in the foreseeable future.
> As for the unforeseeable future, I don't know ;-)
>
>     Brian
>
> On 17/01/2017 14:10, Lorenzo Colitti wrote:
> > Yep. It's an arbitrary choice, just like the choice to make IPv6
> addresses
> > 128 bits long, or the choice to make the header 40 bytes long. That
> doesn't
> > mean we should change it.
> >
> > On Tue, Jan 17, 2017 at 7:23 AM, Brian E Carpenter <
> > brian.e.carpenter@gmail.com> wrote:
> >
> >> 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
> >>>>>
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> >>> .
> >>>
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>
>