Network-level properties of modern anonymity systems

This paper shows the network-level view of the behaviour of two popular and deployed anonymity systems; Tor and JAP (AN.ON). The analysis uses the fact that both of them depend on TCP (Transmission Control Protocol) and shows cases when network conditions may affect the systems’ operations. The main topics are: on-off traffic, difference in available bandwidth between peers, and usage of the window mechanism in the TCP. The analysis is divided into two parts: from both the sender’s and receiver’s point of view. We present the results of experiments made on live systems, showing that the analyzed effects may be encountered in practice.