Re: [dhcwg] Next step(s) for draft-ietf-dhc-stable-privacy-addresses -> abandon work? / IA_NA applicability

[Fernando Gont <[e-mail]>]

On 04/14/2015 02:49 PM, Bernie Volz (volz) wrote:
>> Ok. I will craft text along these lines. Among other things,
>> discuss DECLINES, note that collisions are expected to be virtually
>> impossible thanks to the address space, etc.
> 
> This is NOT true at all (collisions virtually impossible). In fact,
> the exact opposite will almost certainly be true.

May I ask that you provide a rationale for that assertion?

Mine is this: the subnet address space is so large that the problem is
essentially a birthday paradox.



> Also think of cases where much smaller spaces than a /64 are being
> used (such as when a server is configured for a start to end range (1
> to 100000)) or when a longer prefix length is being used (/96) for
> assigning addresses.

That is true. In the first version of the I-D we didn't support ranges.
Now we do, and we should certainly put a huge warning that the address
space should be huge, or things don't work as expected.

If you ask me, I'd say that the standard subnet size is /64. And if you
have a /64 but are assigning addresses from, say, a /110, that's where
the flaw relies. And if you just want to keep some part of the address
space for assigning static addresses to servers, then grab a small
address pool for that, and use the rest for the random/stable addresses
-- but not the other way around!

Thanks!

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