Methodically Modeling the Tor Network.

Live Tor network experiments are difficult due to Tor's distributed nature and the privacy requirements of its client base. Alternative experimentation approaches, such as simulation and emulation, must make choices about how to model various aspects of the Internet and Tor that are not possible or not desirable to duplicate or implement directly. This paper methodically models the Tor network by exploring and justifying every modeling choice required to produce accurate Tor experimentation environments. We validate our model using two state-of-the-art Tor experimentation tools and measurements from the live Tor network. We find that our model enables experiments that characterize Tor's load and performance with reasonable accuracy.