Analyzing peer behavior in KAD

Steiner, Moritz; En-Najjary, Taoufik; Biersack, Ernst W
Research report RR-07-205

Distributed hash tables (DHTs) have been actively studied in literature and many different proposals have been made on how to organize peers in a DHT. However, very few DHTs have been implemented in real systems and deployed on a large scale. One exception is KAD, a DHT based on Kademlia, which is part of eDonkey2000, a peer-to-peer le sharing system with several million simultaneous users. We have been crawling KAD continuously for about six months and obtained information about geographical distribution of peers, session times, peer availability, and peer lifetime. We also evaluated to what extent information about past peer uptime can be used to predict the remaining uptime of the peer. Peers are identied by the so called KAD ID, which was up to now assumed to remain the same across sessions. However, we observed that this is not the case: There is a large number of peers, in particular in China, that change their KAD ID, sometimes as frequently as after each session. This change of KAD IDs makes it difcult to characterize end-user availability or membership turnover. By tracking end-users with static IP addresses, we could measure the rate of change of KAD ID per end-user.

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