Disconnecting to Connect: understanding Optimistic Disconnection in BitTorrent

The significance of BitTorrent motivated various studies focused on modeling and evaluating the protocol characteristics and its current implementations in the Internet. So far, however, no work has investigated Optimistic Disconnect (OD), an ad hoc connection management mechanism widely employed in BitTorrent agents. OD allows a peer to search for "better" neighbors in the swarm by disconnecting peers from the current neighborhood and connecting to others. This paper presents an extensive experimental evaluation to study and quantify potential benefits of OD, such as average download time and topology robustness. We evaluate different scenarios and the impact of factors such as average peer reachability and arrival pattern. We found that OD generally improves the overall performance of the swarm (in up to 30% in the evaluated scenarios), while improving the robustness of its topology.