Showing papers by "Ye Tian published in 2007"

An analytical study on optimizing the lookup performance of distributed hash table systems under churn

Abstract: SUMMARY The phenomenon of system churn degrades the lookup performance of distributed hash table (DHT) systems greatly. To handle the churn, a number of approaches have been proposed to date. However, there is a lack of theoretical analysis to direct how to make design choices under different churn rates and how to configure their parameters optimally. In this paper, we analytically study three important aspects on optimizing DHT lookup performance under churn, i.e. lookup strategy, lookup parallelism and lookup key replication. Our objective is to build a theoretical basis for designers to make better design choices in the future. We first compare the performance of two representative lookup strategies—recursive routing and iterative routing—and explore the existence of better alternatives. Then we study the effectiveness of lookup parallelism in systems with different churn rates and show how to select the optimal degree of parallelism. Owing to the importance of key replication on lookup performance, we also analyze the reliability of the replicated key under two different replication policies, and show how to perform proper configuration. Besides the analytical study, our results are also validated by simulation, and Kad is taken as a case to show the meaningfulness of our analysis. Copyright c � 2007 John Wiley & Sons, Ltd.

Performance analysis and improvement for BitTorrent- like file sharing systems

Abstract: SUMMARY In this paper, we present a simple mathematical model for studying the performance of the BitTorrent (http://www.bittorrent.com) file sharing system. We are especially interested in the distribution of peers in different states of the download job progress. With the model we find that the distribution of the download peers follows an asymmetric U-shaped curve under the stable state, due to BitTorrent’s unchoking strategies. In addition, we find that the seeds’ departure rate and the download peers’ abort rate will influence the peer distribution in different ways notably. We also analyze the content availability under the dying process of the BitTorrent file sharing system. We find that the system’s stability deteriorates with decreasing and unevenly distributed online peers, and BitTorrent’s built-in ‘tit-for-tat’ unchoking strategy could not help to preserve the integrity of the file among the download peers. We propose an innovative ‘tit-for-tat’ unchoking strategy which enables more peers to finish the download job and prolongs the system’s lifetime. By playing our innovative strategy, download peers could cooperate to improve the stability of the system by making a trade-off between the current downloading rate and the future service availability. Finally, experimental results are presented to validate our analytical results and support our proposals. Copyright © 2007 John Wiley & Sons, Ltd.

Performance analysis and improvement for BitTorrent-like file sharing systems: Research Articles

Abstract: In this paper, we present a simple mathematical model for studying the performance of the BitTorrent () file sharing system. We are especially interested in the distribution of peers in different states of the download job progress. With the model we find that the distribution of the download peers follows an asymmetric U-shaped curve under the stable state, due to BitTorrent's unchoking strategies. In addition, we find that the seeds' departure rate and the download peers' abort rate will influence the peer distribution in different ways notably. We also analyze the content availability under the dying process of the BitTorrent file sharing system. We find that the system's stability deteriorates with decreasing and unevenly distributed online peers, and BitTorrent's built-in ‘tit-for-tat’ unchoking strategy could not help to preserve the integrity of the file among the download peers. We propose an innovative ‘tit-for-tat’ unchoking strategy which enables more peers to finish the download job and prolongs the system's lifetime. By playing our innovative strategy, download peers could cooperate to improve the stability of the system by making a trade-off between the current downloading rate and the future service availability. Finally, experimental results are presented to validate our analytical results and support our proposals. Copyright © 2007 John Wiley & Sons, Ltd.