Re: Issues Raised in Chair Review of <draft-ietf-6man-rfc4941bis-05 >

[Fernando Gont <[e-mail]>]

On 27/1/20 20:24, Brian E Carpenter wrote:
> On 28-Jan-20 10:31, Fernando Gont wrote:
>> Hello, Bob,
>>
>> On 27/1/20 14:17, Bob Hinden wrote:
>>> Ole and I did a chairs review of <draft-ietf-6man-rfc4941bis-05>.   Our comments are below.
> 
> <snip>
> 
>>>>     2.  The Interface Identifier is obtained by taking as many bits from
>>>>         the random number obtained in the previous step
>>>>         as necessary.  Note: there are no special bits in an Interface
>>>>         Identifier [RFC7136].
>>>>
>>>>            We note that [RFC4291] requires that the Interface IDs of all
>>>>            unicast addresses (except those that start with the binary
>>>>            value 000) be 64 bits long.  However, the method discussed in
>>>>            this document could be employed for generating Interface IDs
>>>>            of any arbitrary length, albeit at the expense of reduced
>>>>            entropy (when employing Interface IDs smaller than 64 bits).
>>>
>>> It get’s a lot worse if the IID is much smaller, for example, an 8 bit IID is not very useful.   Suggest removing this paragraph or expand it.   The current text doesn’t add very much value.
>>
>> This text was pretty much borrowed from RFC7217. The motivation for it
>> is to keep the hardcoded value of "64" where it belongs (RFC4291
>> ), rather than explicitly repeat "64" here which wuold be a suboptimal
>> spec approach. So the text essentially means "You are going to pick 64
>> bits because that's what rfc4291 requires for unicast addresses that
>> start with binary 000, but you could actually use this algorithm for any
>> IID length).
> 
> I think that is a useful point. We did discuss the privacy implications of very short IIDs in https://tools.ietf.org/html/rfc7421#section-4.5 if you want a reference.

How about adding "The privacy implications of the IID length are 
discussed in [RFC7421]" at the end of that para?

Thanks!

Cheers,
-- 
Fernando Gont
SI6 Networks
e-mail: [e-mail]
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