![]() Our model takes only peer out-degrees as input, as out-degree has the strongest correlation with peer cooperation. We use this finding to propose a new regression-based model to predict peer cooperation from its past centrality. In this article we use data collected from SopCast, a popular P2P live application, to show that there is high correlation between peer centrality-out-degree, out-closeness, and betweenness-in the P2P overlay graph and peer cooperation. ![]() However, the effectiveness of these applications depends largely on user (peer) cooperation. The Peer-to-Peer (P2P) architecture has been successfully used to reduce costs and increase the scalability of Internet live streaming systems. Using the key insights of this analysis, scalable and effective algorithms are designed in order to collect, store and aggregate information in decentralized reputation systems. The socially rich available information of online communities allows the analysis of user behavior and its evolution over time. To face these challenges, this thesis explores algorithms that exploit the graph structure induced by the user interactions in decentralized reputation systems. Due to the highly dynamic behavior of users and the scarcity of resources, several challenging scalability and security issues arise. This thesis studies reputation systems for decentralized networks such as distributed online social networks, online markets on mobile devices, and P2P networks. They differ from their offline counterparts in their large number of participants spread around the world, their explicit design, and the variety of defector strategies. Online reputation systems effectively establish trust among strangers by aggregating the history of user interactions in one reputation value per user. Establishing trust among strangers is essential for the functionality of these communities but challenging, as well. In online communities, users frequently interact with strangers in order to buy and sell products, watch videos, educating themselves, and playing games. Based on the structural properties of the bottleneck-links, we also give a deep discussion about the factors of bottleneck-delays at last, which demonstrates queuing delay is a key factor of bottleneck-delay. Experiment results show that two ends of a bottleneck-link are usually located in the same country, and the links with a large number of entrances (in-degrees) and few number of exits (out-degrees) or the average shallower links are prone to leading to bottleneck-delays. In order to further study the features of bottleneck-delay, we propose an IP united mapping scheme which combines the IP centralized mapping with the IP geographic mapping. In this paper, we utilize real measured probing data to conduct a statistical analysis of the relationship between one-way delay and bottleneck-delay, and demonstrate that bottleneck-delay appears in 70 % of the paths in Internet. To accurately identify the delays at bottleneck-links is a fundamental approach to study the delay feature of Internet, and is beneficial to the design of some efficient distributed algorithms. Especially, the delays at some bottleneck-links of a path account for a large proportion of the End-to-End delay. End-to-End delay is an important performance metric to evaluate the performance of many Internet multimedia applications such as, Voice Over IP (VOIP), online gaming, cloud computing etc.
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