[tor-dev] Reduce RTT for preemptively built circuits (GSoC)

Ian Goldberg iang at cs.uwaterloo.ca
Sat Jun 8 14:29:11 UTC 2013

On Fri, Jun 07, 2013 at 07:38:44PM +0200, ra wrote:
> Hello everyone!
> During this year's Google Summer of Code I[0] will be working on reducing the 
> Round-Trip-Time (RTT) for preemptively built circuits.[1] My mentors are Mike 
> and Aaron.
> A brief summary of the project:
> RTTs of circuits can be measured by violating the exit policy of the exit node 
> and the resulting error can be timed in a measuring client. It is assumed that 
> the RTTs are Fréchet-distributed which could be used to reject a preemptively 
> built circuit if its RTT is below a certain threshold value.
> A basic algorithm will be implemented to gather the required data for further 
> statistical analysis which should help answering open questions like:
> • Are the RTTs Fréchet-distributed?
> • Does this strategy make new attacks feasible?
> • How many probes per circuit are needed to do reasonable estimations?
> • How much additional load is added to the network?
> • What is an appropriate cut-off percentile?
> • Does the strategy work in terms of anonymity and performance?
> • Does the RTT vary for destination ports? (This might be the case for 
> destination ports that occur rarely in exit policies.)
> • Does this strategy also work if guard nodes are congested?
> Best,
> Robert
> [0] "ra_"  on OFTC
> [1] http://www.google-melange.com/gsoc/project/google/gsoc2013/ra_/19001


If I'm understanding the above correctly, this sounds related to our
congestion-aware path selection work:

It's not exactly the same, but I just wanted to ensure you were aware of

[Cc: Tao Wang, the lead author on that paper.]


   - Ian

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