[tor-dev] Status report - Stream-RTT

ra r_a at lavabit.com
Fri Jul 12 20:25:26 UTC 2013

Hi all!

I started a little late on this years GSoC project[0] which is about reducing 
the RTT of preemptively built circuits. Since begin of July I have been 
working on scripts for Tor path generation and Stream-RTT probing.

For the path generation script "path_finder.py" I decided not to reimplement 
Tor's path generation logic but to ask a Tor client to choose a path without 
actually building it. I have written two small patches for Tor which implement 
the following new control commands:
-) "DUMPGUARDS" removes all entry guards. (This might also be handy 
to work around the path selection strangeness when guards are disabled[1]).
-) "FINDPATH" tells the Tor client to generate a path but do not build a 
circuit from it.
To verify the correctness of the approach I am currently generating a few 
million paths and will look into the distribution of nodes.

The Stream-RTT-probing script "rttprober.py" is also in a working state. 
Though it needs some more testing, it is already able to spawn multiple 
threads where each builds a circuit and runs a number of probes on that 
circuit, measuring the RTTs of the stream and the circuit build time. I will 
hopefully be able to get useful Stream-RTT-data soon to tackle the first 
interesting questions.

All scripts and patches are available online[2].


[0] https://www.google-melange.com/gsoc/project/google/gsoc2013/ra_/19001
[1] https://trac.torproject.org/projects/tor/ticket/9188
[2] https://bitbucket.org/ra_/tor-rtt
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