Abstract
In a peer-to-peer file-sharing system, a free-rider is a node which downloads files from its peers but does not share files to other nodes. Analyzing the free-riders’ impact on system throughputs is essential in examining the performance of peer-to-peer file-sharing systems. We find that the free-riders’ impact largely depends on nodes behavior, including their online time and greed of downloading files. We extend an existing peer-to-peer system model and classify nodes according to their behavior. We focus on two peer-to-peer architectures: centralized indexing and distributed hash tables. We find that when the cooperators in a system are all greedy in downloading files, the system throughput has little room to increase while the cooperators throughput degrade badly with the increasing percent of greedy free-riders in the system. When all the cooperators are non-greedy with long average online time, the system throughput has much room to increase and the cooperators throughput degrade little with a high percent of greedy free-riders in the system. We also find that if a system can tolerate a high percent of greedy free-riders without suffering much throughput degradation, the system must contain some non-greedy cooperators that contribute great idle service capacity to the system.
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Foundation item: the National High Technology Research and Development Program (863) of China (No. 2007AA01Z457), and the Shanghai Science and Technology Development Funds (No. 07QA14033)
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Wang, K., Li, Jh. & Pan, L. Free-riders impact on throughputs of peer-to-peer file-sharing systems. J. Shanghai Jiaotong Univ. (Sci.) 14, 273–278 (2009). https://doi.org/10.1007/s12204-009-0273-2
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DOI: https://doi.org/10.1007/s12204-009-0273-2