[tor-bugs] #3277 [Analysis]: Analyze how long after earning the HSDir flag relays go away

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#3277: Analyze how long after earning the HSDir flag relays go away
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 Reporter:  karsten   |          Owner:     
     Type:  task      |         Status:  new
 Priority:  normal    |      Milestone:     
Component:  Analysis  |        Version:     
 Keywords:            |         Parent:     
   Points:            |   Actualpoints:     
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 Relays that are running for at least 24 hours get the HSDir flag from the
 directory authorities.  We should find out how long after after earning
 the HSDir flag relays go away.

 In a first analysis we'll look at HSDir sessions, that is, intervals
 between a relay earning the HSDir flag and going away.  The shortest HSDir
 session would be 0 hours when a relay loses the HSDir flag right after
 obtaining it.  The longest HSDir session might be 1 year, which is the
 analysis interval, if a relay never goes offline.

 Note that the session time resolution is 1 hour, because of the consensus
 publication interval.  If a relay goes away 15 minutes after receiving the
 HSDir flag, we won't notice until the end of the hour.  In that case we
 assume that the relay disappeared after 0 minutes.

 The attached graph shows HSDir session times as an empirical cumulative
 distribution function plot.  It shows what fraction of HSDir session is at
 least ''x'' hours long.  For example, all sessions are by definition at
 least 0 hours long, but only slightly under 90 % of these sessions last
 for at least 1 hour.

 I'm not sure what the exact research question here is and whether this
 analysis answers this question.  Thoughts?

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/3277>
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