Chinese Journal of Computers   Full Text
Title	Improving the Performance of Payment Mechanism Based P2P Application with Altruistic Nodes
Authors	PENG Dong-Sheng LIN Chuang LIU Wei-Dong
Address	(Department of Computer Science and Technology, Tsinghua University, Beijing 100084)
Year	2008
Issue	No.6(953—959)
Abstract &   Background	Abstract While using payment mechanism in P2P resource-sharing application encourages users to share resources in exchange for better services, the disadvantage is that the user’s ability to earn money is unbalanced such that some users can hardly get services. By introducing some altruistic nodes to provide the guaranteed services, the availability of the network can be improved. The performance of the network with altruistic nodes is modeled and analyzed using queueing theory. Parameters of average request waiting time, percentage of the requests served by altruistic nodes and ratio of the altruistic nodes are formulated, which can be used as guidelines to the system performance evaluation and optimization. Keywords performance analysis; queueing theory; modeling; payment mechanism; P2P Background This work is supported in part by the National Natural Science Foundation of China under grant No.90412012, and the National Grand Fundamental Research 973 Program of China under grant No.2006CB708301. This paper focuses on the payment-based incentive mechanism for P2P application and its performance analysis and optimization. "Free-riding" is the most common malicious behavior in P2P applications which degrades the availability of such systems greatly. Incentive mechanism is an effective countermeasure to this problem which encourages end users to share their resources in exchange for better services from others. Distributed payment mechanism, which imitates the economic behaviors in our social lives, is widely studied because of the similarity between P2P network and social network. Most of the related research works focus on implicating payment mechanism into the distributed P2P environment and eliminating its inherent defects such as deflation and inflation. Little literatures concerned with the performance analysis of the payment mechanism. Research interests of this group include QoS and performance evaluation of computer networks. In this paper, the authors model and analyze the performance of payment mechanism based P2P application using queuing theory. As to the disadvantage that the user’s ability to earn money is unbalanced such that some users can hardly get services, the authors introduce some altruistic nodes to provide the guaranteed services. The performance improvement is analyzed. Parameters of average request waiting time, percentage of the requests served by altruistic nodes and ratio of the altruistic nodes are formulated, which can be used as guidelines to the system performance evaluation and optimization.