Matt,
Your point is good, but there must be something wrong with your math.
Christian's point is (I assume) that with a number space of 2^36, when you
select 2^19 random values you start running into a reasonable risk of two of
those random values being the same.
Your equation (N^2/2^18) doesn't seem to take into account the 2^36 number,
and concludes with a probability (0.1%) that strikes me as very high. It
would mean that of Christian's 1,000,000 sites, 1000 of them would have this
problem, which is a lot of sites...
Am I not getting something?
PF
----- Original Message -----
From: "Matt Crawford" <[EMAIL PROTECTED]>
To: "Christian Huitema" <[EMAIL PROTECTED]>
Cc: "Paul Francis" <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]>
Sent: Tuesday, February 20, 2001 8:37 AM
Subject: Re: Wade through the archives (was Re: another renumbering
question)
> > 1) Picking numbers at random is easy, but you need a good random
> > generator, and besides you hit the birthday paradox with 2^^19 entries,
> > i.e. less than a million. There are way more than 1 million potential
> > sites.
>
> You don't care about the existence of any pair of duplicates -- only
> about a duplication with a site you eventually expose your private
> address space to. If everyone picks an unbiased random site id, and
> you connect in that way to N sites, the chance of a duplication is
> only around N^2 / 2^19.
>
> If you reserved half the space for the number-tsar to allocate
> uniquely and half for random picks, the chance of hitting a
> duplication problem (including by connecting to someone with the same
> site id as your site and connecting to two which chose the same) is
> not more than about N^2 / 2^18 -- 0.1% if you connect 16 sites -- and
> far less if you and they are mostly from the unique-numbered camp.
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