[tor-bugs] #1854 [Analysis]: Investigate raising the minimum bandwidth for getting the Fast flag

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Mon Nov 26 20:07:33 UTC 2012


#1854: Investigate raising the minimum bandwidth for getting the Fast flag
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 Reporter:  arma                       |          Owner:  arma             
     Type:  task                       |         Status:  needs_information
 Priority:  normal                     |      Milestone:                   
Component:  Analysis                   |        Version:                   
 Keywords:  performance loadbalancing  |         Parent:                   
   Points:                             |   Actualpoints:                   
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Comment(by karsten):

 Replying to [comment:41 iang]:
 > What's going on at the right end of the linf graph there?

 You mean why is it skyrocketing and then dropping to almost zero?  I think
 when there's only 1 relay left, the probability of it being picked grows
 to 100%, so linf is 100% minus its previous probability of being picked.
 And when no relay is left, linf goes down to the maximum probability of a
 relay being picked in the pristine consensus that now cannot be picked
 anymore.

 > Other than that, the plot shows that setting the cutoff to 1 MB/s (using
 only the top 400 relays or so) would affect the choice of relays in a tiny
 amount I can't read from the graph.  (Can you make that graph log/log?)

 [https://trac.torproject.org/projects/tor/attachment/ticket/1854/linf-min-
 adv-bw-2012-11-26-a.pdf Attached].  (I left the original graph in and
 added another graph for log/log, because number of relays looks funny on a
 log scale and there's no easy way to use different scales for both sub
 graphs.)

 > What is the linf comparison to?  A cutoff of 20 KB/s?  No cutoff?  There
 are relays appearing in the upper plot with speeds < 20 KB/s.

 No cutoff, that is, comparing to the pristine consensus where any relay
 could be picked.  That's how linf is defined in the script right now.  We
 can change that, but new results would be at least 9+ hours away.

-- 
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/1854#comment:43>
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