[tor-bugs] #3044 [Analysis]: At what bandwidth threshold is being a dir mirror unwise?

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#3044: At what bandwidth threshold is being a dir mirror unwise?
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 Reporter:  arma                   |          Owner:     
     Type:  task                   |         Status:  new
 Priority:  normal                 |      Milestone:     
Component:  Analysis               |        Version:     
 Keywords:  performance bootstrap  |         Parent:     
   Points:                         |   Actualpoints:     
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Changes (by arma):

 * cc: chiiph (added)


Comment:

 Tomas: a good first experiment here would be to look at the variance for
 bootstrapping times. That is, when you start up a Tor client with no
 cached info, it will fetch a consensus from an authority, and fetch
 descriptors from random (weighted by bandwidth) directory mirrors from the
 consensus. If it picks slow directory mirrors, it will take a while. How
 long is the mean, median, 90th percentile, etc?

 If you change the selection algorithm that the Tor client uses (e.g. to
 ignore choices with bandwidth less than N, and weight by bandwidth among
 the remaining ones), you can probably cut off part of the long tail.
 Another variation on the selection algorithm is to ignore mirrors that
 don't have the Guard flag. Another variation is to look at fetching v3
 consensus + descriptors versus fetching v3 microconsensus plus
 microdescriptors.

 You should keep in mind while doing the experiment that you are comparing
 the situation where 1 user chooses differently and n-1 users choose with
 the old algorithm. So it wouldn't directly capture the case where all n
 users choose with the new algorithm. If the experiment goes well, we could
 maybe put the threshold in the consensus and have clients and/or mirrors
 obey it, to do a more realistic experiment; but that would take a few
 years before enough Tors upgrade.

-- 
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/3044#comment:3>
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