Analyzing the drawbacks of node-based delays in Tor

Abstract

Tor Network is a low-latency anonymity and censorship resistance network, which relaying traffics through onion routers before being forwarded to the destination. The distribution of trust offered by Tor creates resilience in the face of compromise and censorship. However, there are performance and usability issues in the Tor network. In this paper, we analyze the delay contributions from the host TCP stack of the Tor relay mode. We measured and analyzed the transfer data passing through the Tor nodes to evaluate the main causes of delays. The experimental analysis show that increasing delays on nodes are affected by the heavy TCP packets queuing, kernel memory exhaustion and TCP advertised window not able to accept more data. We present our experimental analysis and measurement results as a prerequisite for addressing the Tor's end-to-end increasing latency and poor usability.