Enhancing Traffic Locality in BitTorrent via Shared Trackers

摘要

The fast-growing traffic of peer-to-peer (P2P) applications, most notably BitTorrent, is putting unprecedented pressure to Internet Service Providers (ISPs). P2P locality has therefore been widely suggested to mitigate the costly inter-ISP traffic. In this paper, we find that even in the most popular ASes (Autonomous Systems), very few individual torrents are able to form large enough local clusters of peers, making state-of-the-art locality mechanisms for individual torrents quite inefficient. Inspired by peers' multiple torrent behavior, we develop a novel framework that traces and recovers the available contents at peers across multiple torrents, and thus effectively amplifies the possibilities of local sharing. We address some key design issues in this framework; in particular, we discuss the detection of peer migration and further explore the trends of improving peers' incentive. We develop a smart detection mechanism with shared trackers, which achieves 45% success rate without any tracker-level communication overhead. Our trace-based simulation results indicate that our framework can successfully reduce the cross-ISP traffic and minimize the possible degradation of peers' downloading experiences.