Re: [Zcip] embeddable zeroconf/ip code

David Brownell wrote:
> 
> Right, but that doesn't matter.  (And do all the Windows an MacOS
> machines all use the same PRNG sequences?  I suspect not... so
> it "must not" matter whether Linux ones use that.)
> 

There are different values of "matter"... as in does it work/not work vs. how 
good is it (how fast does it converge, how few collisions do we get.)

> Consider:  Machine A uses srandom(), B uses seed48().  Each uses
> a different seed.  What we care about is that the random host number
> they get next -- random() or lrand48(), modulo (2^16 - 512) - not
> collide "too much" with each other or machines C, D, E, etc.  We
> know that some collisions are guaranteed in larger networks given
> that small address space; OK, we'll recover from collisions.
> 
> You're talking about a different property:  that when both use the
> same seed and seed API, a collision is guaranteed.  That can
> be guaranteed with seed48() because it's fully specified, but not
> with srandom() since that PRNG's math isn't fully specified.
> 
> Or am I missing something?  The only real issue I can see here
> with PRNG is ensuring the sequences repeat no sooner than every
> 2^16 - 512 samples.
> 

Again, it's a quality of implementation issue.

	-hpa



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