Re: IID length text

[Brian E Carpenter <[e-mail]>]

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 <
> [e-mail]> wrote:
> 
>> On 17/01/2017 09:42, Behcet Sarikaya wrote:
>>> On Mon, Jan 16, 2017 at 2:27 PM, Alexandre Petrescu
>>> <[e-mail]> 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
>>>>> [e-mail]
>>>>> Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6
>>>>> --------------------------------------------------------------------
>>>>>
>>>>
>>>> --------------------------------------------------------------------
>>>> IETF IPv6 working group mailing list
>>>> [e-mail]
>>>> Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6
>>>> --------------------------------------------------------------------
>>>>
>>> .
>>>
>>
>> --------------------------------------------------------------------
>> IETF IPv6 working group mailing list
>> [e-mail]
>> Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6
>> --------------------------------------------------------------------
>>
>