[tor-bugs] #6232 [Metrics Website]: Add entropy-over-time graph to network page

Tor Bug Tracker & Wiki torproject-admin at torproject.org
Sun Jun 24 08:32:40 UTC 2012


#6232: Add entropy-over-time graph to network page
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 Reporter:  arma             |          Owner:     
     Type:  enhancement      |         Status:  new
 Priority:  normal           |      Milestone:     
Component:  Metrics Website  |        Version:     
 Keywords:                   |         Parent:     
   Points:                   |   Actualpoints:     
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 We have number-of-relays-over-time, and amount-of-bandwidth-over-time. We
 don't yet have entropy-of-consensus-weights-over-time.

 The way to get it is to sum up all the weights in the consensus, then
 calculate, for each relay in the consensus, the probability it will be
 chosen (its weight divided by sum of weights) times - log_2 of that
 probability. Then sum up all those calculations, and you have the shannon
 entropy of that consensus. As an intuitive check, if the shannon entropy
 is b bits, that's equivalent to a Tor network with 2**b nodes that all
 have the same weights.

 http://en.wikipedia.org/wiki/Entropy_%28information_theory%29 for plenty
 more background.

 Damian said he'd be happy to use stem to help extract the numbers, so from
 Karsten's perspective hopefully this is just a graphing exercise.

 Once we have this one going, I will likely ask for the same sort of graph
 as if we used descriptor bandwidths for weights (that is, as if we didn't
 have bwauths running), so we can compare how much entropy we're giving up
 in exchange for the performance improvements we get from bwauths.

 And after that, I'll want to know about the subset of nodes that have the
 Guard flag, and the subset that have the Exit flag. One step at a time, I
 know, but I figure I should give a sense of the scope of the future plans
 too. Thanks!

-- 
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/6232>
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