Network Service Availability

P2P network has been one of the hottest research issues for its attractive advantages in the application areas like file sharing, content distribution, distributed storage, distributed computing, etc. However, the autonomous nature of nodes in P2P network leads to the fairness problem and the trust problem in P2P service management, which seriously impact the service availability of P2P environment. Free-riding is the most important embodiment of P2P fairness problem. The selfishness of free-riders may lead to the lack of service resources and the deterioration of service quality in P2P network. On the other hand, the lack of trust in P2P environment leads to the problems such as service fraud and routing attack, which seriously harm the service quality, reliability and security in P2P network. This dissertation concentrates on alleviating the negative impact of node autonomy on the service availability in P2P network, through the design of the trust management mechanism and the incentive mechanism for nodes. The main contributions of this dissertation are as follows:(1) A distributed node information management scheme named DNIM for P2P networks is proposed, which helps nodes understand each other's behavior characteristic before the trust establishment. DNIM adapts well to P2P environment, by distributing the responsibility of node information management to all the nodes in the underlying structured P2P network. By the redundant storage mechanism and the voting strategy for node information, DNIM ensures the storage security of node information in a probabilistic sense. Furthermore, by the node information transfer and backup mechanism, DNIM alleviates the impact of network dynamics on the node information management.(2) To alleviate the impact of node's selfishness on the file availability in structured P2P networks, a reputation scheme named GFARep for guarding file availability is proposed. Based on the concept of anonymous monitoring query, GFARep effectively gathers the selfish behavior of nodes in the process of file publication and lookup, which may harm the file availability. Moreover, by aggregating the current behavior, historical behavior and the behavior trend of nodes into the reputation evaluation, GFARep ensures the fairness of reputation mechanism in reflecting the real behavior characteristic of nodes. Based on the reputation mechanism, the file access control mechanism adopted by GFARep provides necessary incentive to encourage the cooperative behavior of nodes.(3) We propose a market model based on P2P data transmission application and analyze the objectives of the provider and the consumer of data transmission service in the market model respectively. The analysis result shows that the providers can contribute to the optimization of service performance of P2P data transmission, on the premise of guaranteeing their benefit. On the light of the analysis, we propose a service incentive scheme named VCOPDT for P2P data transmission based on the concept of virtual currency. Through the concepts of market and virtual currency payment, VCOPDT provides incentive to encourage the provision of data transmission service. On the other hand, by the transaction auditing mechanism and the bonus mechanism, VCOPDT also encourages the service providers to contribute to the optimization of service performance and improve the satisfaction of consumers with the data transmission service.(4) We propose a reputation scheme named GRRep, to reduce the impact of node autonomy on the availability of routing mechanism in structured P2P network. To track the short-term and long-term behavior of nodes in the routing mechanism, GRRep adopts two reputation mechanisms working on different levels, i.e., the local reputation mechanism and the global reputation mechanism. The local reputation mechanism helps a node guarantee the safety of its routing table and neighbor set, based on its local routing experience. On the other hand, the global reputation mechanism is built on the top of the local trust mechanism. With the help of the trust transfer between nodes, the global reputation mechanism ensures its objectivity in reflecting the long-term routing behavior of nodes. Furthermore, by making reputation scores publicly available, the global reputation mechanism helps nodes establish the trust relationship between each other from the global perspective. Based on the reputation mechanisms, GRRep encourages the cooperative behavior of nodes and reduces the impact of node autonomy on the routing mechanism.