Showing papers by "Gyorgy Dan published in 2009"

Dynamic swarm management for improved BitTorrent performance

Abstract: BitTorrent is a very scalable file sharing protocol that utilizes the upload bandwidth of peers to offload the original content source. With BitTorrent, each file is split into many small pieces, each of which may be downloaded from different peers. While BitTorrent allows peers to effectively share pieces in systems with sufficient participating peers, the performance can degrade if participation decreases. Using measurements of over 700 trackers, which collectively maintain state information of a combined total of 2.8 million unique torrents, we identify many torrents for which the system performance can be significantly improved by re-allocating peers among the trackers. We propose a light-weight distributed swarm management algorithm that manages the peer torrents while ensuring load fairness among the trackers. The algorithm achieves much of its performance improvements by identifying and merging small swarms, for which the performance is more sensitive to fluctuations in the peer participation, and allows load sharing for large torrents.

Delay Asymptotics and Scalability for Peer-to-Peer Live Streaming

Abstract: A large number of peer-to-peer streaming systems have been proposed and deployed in recent years. Yet, there is no clear understanding of how these systems scale and how multipath and multihop transmission, properties of all recent systems, affect the quality experienced by the peers. In this paper, we present an analytical study that considers the relationship between delay and loss for general overlays: we study the trade-off between the playback delay and the probability of missing a packet and we derive bounds on the scalability of the systems. We present an exact model of push-based overlays and show that the bounds hold under diverse conditions: in the presence of errors, under node churn, and when using forward error correction and various retransmission schemes.