Research Of The Search Strategy In Unstructured P2P Networks

With the rapid development of Internet, there are more and more information resources online, so it is more and more difficult to search and retrive resources. The emergence of the Peer-to-Peer (P2P) networks solves this problem.P2P is a new network application model which is different from traditional Client/Server(C/S) model. In P2P networks, each node not only plays a role of server that provides the service but also plays a role of client that enjoys the users of resources, and the resources can be passed directly among nodes without the centralized server. The model of the P2P networks is the reason to sovle the difficulty of retriving resources.P2P networks are divided into unstructured P2P networks and structured P2P networks. Unstructured P2P network is abroad used because it is simple and robust, and it adopts the traditional Flooding search strategy. The number of the messages increases exponentially as the network grows, and most of them are redundant messages which lead to consume a lot of bandwidth. Therefore, it is necessary to propose the modified search strategies.In the thesis, we present two modified search strategies in order to solve the problems in unstructured P2P networks, such as redundant messages, inefficient search and high network cost. One is based on the attractive factor. When the node who receives the resource request message selects the next forwarding node, it accords to a probability formula. The larger the sum of one node's degree and attractive factor, the greater the probability of receving the resource request message. The simulation and results analysis prove that the performance of this strategy is better than the Flooding search strategy. Another strategy is based on the local world. This strategy adds the concept of the local world to the former strategy. The node only selects one node in it's local world as the next forwarding node. The simulation and results analysis prove that the performance of this strategy is better than the Flooding search strategy and the former modified strategy.