[Nrg-l] Remainder - October 22 @ 3pm

Jorge Londoño jmlon at cs.bu.edu
Fri Oct 19 10:56:02 EDT 2007

*Title:* Clustering and Sharing Incentives in BitTorrent Systems

*By*: Arnaud Legout (INRIA), Nikitas Liogkas, Eddie Kohler, Lixia Zhang 

Peer-to-peer protocols play an increasingly instrumental role in Internet
content distribution. It is therefore important to gain a complete
understanding of how these protocols behave in practice and
how their operating parameters affect overall system performance.
This paper presents the first detailed experimental investigation of
the peer selection strategy in the popular BitTorrent protocol. By
observing more than 40 nodes in instrumented private torrents, we
validate three protocol properties that, though believed to hold, have
not been previously demonstrated experimentally: the clustering of
similar-bandwidth peers, the effectiveness of BitTorrent's sharing
incentives, and the peers' high uplink utilization. In addition, we
observe that BitTorrent's modified choking algorithm in seed state
provides uniform service to all peers, and that an underprovisioned
initial seed leads to absence of peer clustering and less effective
sharing incentives. Based on our results, we provide guidelines for
seed provisioning by content providers, and discuss a tracker protocol
extension that addresses an identified limitation of the protocol.

This paper appeared in Sigmetrics 2007. The paper is available here:

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