[tor-bugs] #7757 [Tor]: Maybe revisit node flag weight calculations

Tor Bug Tracker & Wiki blackhole at torproject.org
Wed Dec 19 03:08:57 UTC 2012


#7757: Maybe revisit node flag weight calculations
-------------------------+--------------------------------------------------
 Reporter:  mikeperry    |          Owner:  mikeperry       
     Type:  enhancement  |         Status:  new             
 Priority:  normal       |      Milestone:  Tor: unspecified
Component:  Tor          |        Version:                  
 Keywords:               |         Parent:                  
   Points:               |   Actualpoints:                  
-------------------------+--------------------------------------------------
 Directory guards (#6526) are going to shift some weight off of middle
 nodes and on to guard nodes. This potentially changes the weights we
 should give to guard nodes for the middle hop (see dir-spec.txt Section
 3.5.3: https://gitweb.torproject.org/torspec.git/blob/HEAD:/dir-
 spec.txt#l1858).

 However, the bandwidth authorities have consistently measured middle nodes
 as too slow, and Guard nodes as too fast, relative to the rest of the
 network on average. Exits come out just about even.

 If I had to guess, most likely middle nodes are bogged down because
 nothing in the flag weight calculations takes into account the load from
 either dirport usage above, or hidden service usage. Directory usage is
 possible to estimate, but hidden service traffic sometimes involves Exits
 (from cannibalized circs), sometimes doesn't (from directly built internal
 circs), and it's nearly impossible to estimate how much of the network
 traffic it occupies...

 So perhaps #6526 will magically correct this imbalance by shifting
 directory traffic from middle nodes to Guards. Or, perhaps it will be too
 much. We should keep an eye on the output of
 https://gitweb.torproject.org/torflow.git/blob/HEAD:/NetworkScanners/statsplitter.py
 either way as the directory guards code is deployed.

-- 
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/7757>
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