[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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Comment(by rransom):

 Replying to [comment:3 karsten]:
 > Replying to [comment:2 Sebastian]:
 > > These results are very interesting. They seem to show bug 1810,
 because after 24+18 hours there's another big drop in relay availability,
 [...]
 >
 > Note that the graph shows HSDir sessions between May 2010 and April
 2011.  Not sure how much these are affected by #1810.
 >
 > > [...] and they also seem to indicate that the move to 25 hours was a
 good idea.
 >
 > Actually, the drop from 0 to 1 hours doesn't look that unusual.  I
 attached another graph that contains "simulations" of assigning flags
 after 25 and 26 hours.  The idea of the simulations is simply to remove
 all 0-hour sessions (all 0-hour and 1-hour sessions) and subtract 1 hour
 (2 hours) from all other sessions.  As you can see, the drop from 0 to 1
 hour is still around 8 % (7 %).  Of course, this comes at the cost of
 having a smaller set of relays with the HSDir flag.  So, it might have
 been a good idea to change the requirement to 25 hours, but I think this
 needs more analysis.

 This ‘simulation’ is bogus.  We used to assign the HSDir flag based on
 whether a relay reports in its descriptor that it has been running for 24
 hours; if a relay dropped from the consensus for 6 out of every 24 hours,
 it would still have been given the HSDir flag immediately every time it
 re-entered the consensus.  Our current HSDir-assignment scheme uses WFU,
 but will still give relays that have run continuously for several days and
 dropped from the consensus for 6 hours each day the HSDir flag immediately
 upon their return.

 Unfortunately, the DAs do not record the ‘rephist’ data that they base
 their votes on, so we don't have enough data to simulate HSDir flag
 assignment accurately.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/3277#comment:4>
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