On Thu, Feb 13, 2020 at 10:26:09AM -0500, Tom Talpey wrote: > > If both src & dst ports are in the high value range you loss those > > hash bits in the masking. > > If src & dst port are both 0xE000, your masked hash equals 0. You'll > > get the same hash if both ports are equal 0xF000. > > Sure, but this is because it's a 20-bit hash of a 32-bit object. There > will always be collisions, this is just one example. My concern is the > statistical spread of the results. I argue it's not changed by the > proposed bit-folding, possibly even damaged. I've always thought that 'folding' by modulo results in an abnormal statistical distribution The point here is not collisions but to have a hash distribution which is generally uniform for the input space. Alex, it would be good to make a quick program to measure the uniformity of the distribution.. Jason
