[tor-bugs] #4489 [Tor Directory Authority]: AuthDirFastGuarantee is too low, harming performance

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#4489: AuthDirFastGuarantee is too low, harming performance
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 Reporter:  arma                        |          Owner:                    
     Type:  defect                      |         Status:  new               
 Priority:  normal                      |      Milestone:  Tor: 0.2.2.x-final
Component:  Tor Directory Authority     |        Version:                    
 Keywords:  performance, loadbalancing  |         Parent:                    
   Points:                              |   Actualpoints:                    
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 Right now the bandwidth cutoff to guarantee the Fast flag (see #4484) is
 20KB. That means anybody with 20KB or more of capacity gets the Fast flag
 for sure.

 But our design had in mind that we'd adapt the assignment of the Fast flag
 to grow as the relays grew, such that the top 7/8 of the relays got it.
 The guarantee was intended to be a security defense against a Sybil
 flooding the network with enough lying relays to push out most honest
 relays.

 At the time we picked 20KB for the guarantee, that was the value for the
 7/8 mark. But right now moria1 would vote the Fast flag only for relays
 with 32KB of capacity or more, if it weren't constrained by this 20KB
 guarantee.

 I think we should change AuthDirFastGuarantee to 100KB while we await
 performance analysis to answer questions like the ones posed in #3946.

-- 
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/4489>
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