Date: Wed, 2 Jun 2004 11:10:57 -0400 From: Barney Wolff <barney@databus.com> To: Andre Oppermann <andre@freebsd.org> Cc: freebsd-net@freebsd.org Subject: Re: net.inet.ip.portrange.randomized=1 hurts Message-ID: <20040602151057.GA39564@pit.databus.com> In-Reply-To: <40BDAEEF.2AECC3F0@freebsd.org> References: <20040602093940.N99493@atlantis.atlantis.dp.ua> <40BDAEEF.2AECC3F0@freebsd.org>
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On Wed, Jun 02, 2004 at 12:41:51PM +0200, Andre Oppermann wrote: > > have 16383 non-repeated port numbers before the first repeat). > > The random generator indeed works badly. If it was truely random it > should generate a collision only every (1/range) on average. Maybe > the arc4random function reuses the same or small number of initial vectors > all over again leading to the same small set of 'randomized' ports. I believe you're seeing the birthday paradox at work, and the expected number before collision is sqrt(N), not N. Is the problem that the two systems have different ideas of MSL? -- Barney Wolff http://www.databus.com/bwresume.pdf I'm available by contract or FT, in the NYC metro area or via the 'Net.
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