[arin-ppml] V6 address allocation policy
mysidia at gmail.com
Sun Jan 17 22:37:52 EST 2010
On Sun, Jan 17, 2010 at 9:02 PM, Henry Yen <arin-mail at aegisinfosys.com> wrote:
> On Sun, Jan 17, 2010 at 10:46:03AM -0500, William Herrin wrote:
>> Not exactly... The analysis in RFC 4193 (ULA addressing) section 3.2.3
>> is technically correct but it may be an example of "lies, damn lies
>> and statistics."
> Is it shorthand for the Birthday Paradox
And the RFC accounts for that, by using the formula
Exp[-N^2 / 2^41]
However... I wonder how 'random' the 40-bit global ID will
actually be in practice.
I realize the RFC suggests a robust procedure for generating it..
But something tells me many sites will be tempted to ignore those
recommendations, and treat ULA much like they treat RFC-1918
That is, they might confuse "random id", for just pick whatever
number occurs to them. Statistically more than should will probably
pick all-bits zero, or 'some convenient numbers' for the global id
Or even, a human picking the global ID might _avoid_ numbers
like 0 or 1234, such that the number has less than a 1/2^40
chance of being picked.
If the actual entropy behind 'global id creation' in practice
turns out to be less than true randomness, then the results
regarding probabiliity of collision are also fallible.
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