Re: IID length text

[Fernando Gont <[e-mail]>]

On 01/16/2017 06:22 PM, Behcet Sarikaya wrote:
> On Mon, Jan 16, 2017 at 2:46 PM, Fernando Gont <[e-mail]> wrote:
>> On 01/16/2017 05:42 PM, 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.
>>
>> 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: [e-mail]
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