A Reputation Algorithm for a Self-Organizing System Based upon Resource Virtualization Dan C. Marinescu, Chen Yu, Gabriela M. Marinescu School of Electrical Engineering and Computer Science University of Central Florida, Orlando, Fl, 32816 Email: (dcm, yuchen, magda)@cs.ucf.edu John P. Morrison and Christoffer Norvik Computer Science Department University College Cork, Cork, Ireland Email: (j.morrison, c.norvik)@cs.ucc.ie October 4, 2007 Abstract In the service-oriented architecture introduced in [10] the reputation affects the prices pro- ducers could ask for their resources, the prices consumers of resources are willing to pay, and the commission charged for every contract. In this paper we introduce the GRB algorithm to quantify the reputations of the participants. The system is self-organizing and this affects the space requirements and the communication complexity of the algorithm. 1 Introduction Traditionally, a service provider in a service-based distributed system owns, or is in total control, of all resources needed to provide that service. Peer-to-peer systems are challenging this paradigm with varying degrees of success. For example, Skype, an Internet phone service provider, surrep- titiously uses selected sites connected to the system as super nodes to route calls; Napster, a file sharing system stores data files on individual sites owned by its subscribers and Video-on-demand attempts to take advantage of data storage on sites scattered around the Internet. The strategy used by these applications and others is motivated by a desire to reduce the cost of providing the service. Current implementations of the peer-to-peer resource sharing philosophy is plagued by prob- lems such as uncertainty regarding the amount of resources available at any instant of time, asym- metry of the communication bandwidth of home access networks (the download bandwidth is generally much higher than the upload one), and lack of system support at the sites providing a fraction of their resources to the community. As a result, such systems are unable to provide Qual- ity of Service (QoS) guarantees or ensure fairness, are vulnerable to malicious attacks, prone to catastrophic failures, as the recent collapse of Skype shows, do not provide security guarantees 1