Title
Throttling Tor bandwidth parasites
Abstract
Tor is vulnerable to network congestion and performance problems due to bulk data transfers. A large fraction of the available network capacity is consumed by a small percentage of Tor users, resulting in severe service degradation for the majority. Bulk users continuously drain relays of excess bandwidth, creating new network bottlenecks and exacerbating the effects of existing ones. While this problem may currently be attributed to rational users utilizing the network, it may also be exploited by a relatively low-resource adversary using similar techniques to contribute to a network denial of service (DoS) attack. Degraded service discourages the use of Tor, affecting both Tor's client diversity and anonymity. Equipped with mechanisms from communication networks, we design and implement three Tor-specific algorithms that throttle bulk transfers to reduce network congestion and increase network responsiveness. Unlike existing techniques, our algorithms adapt to network dynamics using only information local to a relay. We experiment with full-network deployments of our algorithms under a range of light to heavy network loads. We find that throttling results in significant improvements to web client performance while mitigating the negative effects of bulk transfers. We also analyze how throttling affects anonymity and compare the security of our algorithms under adversarial attack. We find that throttling reduces information leakage compared to unthrottled Tor while improving anonymity against realistic adversaries.
Year
Venue
Keywords
2012
NDSS
network congestion,new network bottleneck,heavy network load,throttling tor bandwidth parasite,bulk data transfer,increase network responsiveness,tor user,network dynamic,available network capacity,network denial,communication network,algorithms,bandwidth,computer networks
DocType
Citations 
PageRank 
Conference
8
0.50
References 
Authors
38
3
Name
Order
Citations
PageRank
Rob Jansen128316.78
Paul Syverson24713457.55
Nicholas Hopper3146995.76