[tor-bugs] #3443 [Tor Client]: Client with low CBT can't switch to a bridge if it's slow

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#3443: Client with low CBT can't switch to a bridge if it's slow
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 Reporter:  arma        |          Owner:                    
     Type:  defect      |         Status:  new               
 Priority:  major       |      Milestone:  Tor: 0.2.3.x-final
Component:  Tor Client  |        Version:                    
 Keywords:  regression  |         Parent:                    
   Points:              |   Actualpoints:                    
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Comment(by ioneyes):

 Tor is capable of tracking quite large ( a ratio I have seen of up to 1:10
 ) differences in response time from varying networks.

 To test this I ran Tor and switched in a slower network (Mobile GSM) and
 then a faster network (DSL) letting it settle in between switching.

 The key is to use a CircuitBuildTimeout that allows for circuits to build
 on the slower network.

 I have a graph that illusrates Tor's 'tracking' ability.

 The graph, Graphs - LAN to Dialup.jpg, reveals ping responses on the left.
 In Blue is the ping time seen on the GSM (slower) network and in green the
 DSL (faster) network.

 It is clearly higher for GSM.

 On the right is the observed Network Reset Timeout as the networks are
 switched with each other. It does seem to cope. The secret is to make sure
 CircuitBuiltTimeout is larger than you largest expected latency in
 seconds.
 Obviously if the network does not allow circuit creation within the
 CircuitBuildTimeout there will be no circuits available to move traffic.

 Or... I have got it all wrong...

-- 
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/3443#comment:15>
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