[address-policy-wg] 2007-05 New Policy Proposal (IPv6 ULA-Central)

Geoff Huston wrote:

> On 5/4/07, Gert Doering <gert at space.net> wrote:
> 
>>
>> Hi,
>>
>> On Fri, May 04, 2007 at 11:54:22AM +0200, Shane Kerr wrote:
>> > The motivation for a version with a central registry however is not so
>> > obvious to me. The only justification I can think of is that you can
>> > be sure not to pick the same /48 as someone else has picked. But the
>> > chances of that are *billions* (that's "thousands of millions" to
>> > British folk) to one!
>>
>> Take the "birthday paradoxon" into account.  Chances for a clash with
>> "someone else in the room" are actually much higher than the chance
>> for a clash with "a *specific* number out of the ame pool".
> 
> 
> 
>   The general solution of
>   the probability of a collision after d draws from n possible values
>   is given by:
> 
>      P = 1 - ((n!) / ((n**d)((n-d)!)))
> 
>   Given that the value for n is 2.199,023,255,552, then the objective
>   is to find the lowest value of d for which P is greater than or equal
>   to 0.5. In this case the value for d  is some 1.24 million.

That formula does apply under the assumption(s) that the draws
will be evenly distributed across the value space, correct?

> http://draft-huston-ipv6-local-use-comments.potaroo.net
> 
>  Geoff
> 
Wilfried.