A Circuit Switching Method for Improving Congestion of Tor Network

The Tor Network is a low-latency anonymity and censorship resistance network, which relaying traffics through series of onion routers (OR) before being forwarded to the destination. Tor is vulnerable to network congestion and performance problems, due to bulk and light traffics are competing to transfer data on a single TCP connection. A large fraction of the available network capacity is consumed by bulk users´ traffic, resulting in higher buffer occupancy and delays for interactive light users. To address the problems, we propose a method of switching the bulk traffic that contributes to increasing delays to another path, which built preemptively at the beginning. This approach allows the light interactive circuits to utilize the bandwidth resources well and, easily writes their cells from the circuit queue to the output buffer and outgoing TCP socket. Our approach of switching bulk circuits in the overloaded ORs comes to effect if the Tor output queues increases beyond the threshold value, and when sending TCP socket is congested and un-writable. Our goal is to reduce the congestion in the ORs and improve the throughput from the incoming traffic (upstream), and outgoing traffic (downstream). Through measurements and evaluation conducted in the live Tor network, we observed that the throughput of the light interactive traffic is improved. The light circuit traffics are no longer forced to wait behind the bulk traffic when transfer their data to the outgoing TCP socket.