[freenet-dev] DNFs and the laws of physics

[Ian Clarke]

If, as has been reported, a node which always DNFs gets an increasing 
number of requests then there is a bug in NGR - plain and simple - and 
it should be easy enough to track down.

*This* should be our focus, not iTTL which seems like [yet another] 
hasty solution to a problem we haven't found yet.

Toad is right to say that calculating tSearchFailed isn't easy, but 
wrong to say that tSearchFailed should be infinite.  Just because 
something is unknown does not imply that it is infinite (you don't know 
my birthday, does that mean its infinite too?).

In fact, tSearchFailed clearly shouldn't be infinite, if it were then we 
would prefer a slow node with pDNF of 0.8 over a fast node with pDNF 
0.8000000000000001.  Clearly that would be silly, ergo we want 
tSearchFailed to be less than infinity.

Estimates are calculated using (simplified):

e = pDF*tDF + pDNF*(tDNF * tSearchFailed)

Provided that tSearchFailed is always > tDF, a node should never prefer 
a node which DNFs over a node where requests succeed, especially when 
pDNF is 1.  Zab's experiments with blackholes suggests that even when 
pDNF is 1, nodes are still routing requests - which suggests a bug.  An 
easy way to debug this might be to include the estimator() calculation 
in the DataRequest such that a blackhole node could see why people keep 
routing to it.

Lets examine the obvious explanations before we start to question the 
laws of physics.
Ian.
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