Unraveling BitTorrent's File Unavailability: Measurements and Analysis

—BitTorrent suffers from one fundamental problem: the long-term availability of content. This occurs on a massivescale with 38% of torrents becoming unavailable within the first month. In this paper we explore this problem by performing two large-scale measurement studies including 46K torrents and 29M users. The studies go significantly beyond any previous work by combining per-node, per-torrent and system-wide observations to ascertain the causes, characteristics and repercussions of file unavailability. The study confirms the conclusion from previous works that seeders have a significant impact on both performance and availability. However, we also present some crucial new findings: (i) the presence of seeders is not the sole factor involved in file availability, (ii) 23.5% of nodes that operate in seedless torrents can finish their downloads, and (iii) BitTorrent availability is discontinuous, operating in cycles of temporary unavailability.

• Type: Journal
• Year: 2010
• Where: P2P
• Authors: Sebastian Kaune, Rubén Cuevas Rumín, Gareth Tyson, Andreas Mauthe, Carmen Guerrero, Ralf Steinmetz
• Keywords: Availability, Communications, Large-scale Measurement Studies, Long-term Availability, P2P 2010