Research On P2P-based Network Resource Search Model

Resources locating is a key issue of P2P network and a research hotspot as well. Based on a network topology, the resources locating models of P2P system are divided into 4 types: Centralized Topology, Decentralized Unstructured Topology, Decentralized Structured Topology and Partially Decentralized Topology. A DHT based Decentralized Structured model, which avoids central managing and broadcast querying, has recently become a focus in the research area. It applies hash function to map the input key of a file to a virtual node, and then sets up a connection with the node through some kind of routing algorithm. The DHT based methods enjoy great advantages of simplicity and extensibility. However, as the keyword space is isolated from the real physical network, the method will disturb the data Locality. As a result, query latency is high while data-downloading speed is low. Typical DHT-based systems include Chord, Pastry, CAN and Tapestry and P-Grid.Based on the careful analysis of principle, realization measures, performance characteristic, advantage and disadvantage of the search models and search algorithms in P2P system, this article takes good consideration of several laws in real world and network (including power-law, Patreo distribution law, Zipf law and Small-World phenomenon and its application etc.) and put forward a newly heuristic DHT mechanism to aim to solving resources locating or searching in P2P system. The relative mathematics formula are also provided and carefully ayalysed. The mechanism picks up several popular data and stores the relative information about those data into an index table in each peer node, and those data can be adjusted by system with the time. It firstly queries in the index table and then turns to the local route table in each peer node and transmit the request to route peer node if not any items were found. Those popular data take on most of the query requests in a given P2P system, hence many requests can be satisfied in a logistic hop. Next, this article uses the mechanism in the P-Grid called HP-Grid and Chord called HChord model both are based on DHT one. The system construction, query, table maintenances and the detailed improved algorithm process are also provided.Further more, this article carried out simulation tests on this mechanism and algorithms in MIT P2Psim simulator, which demonstrate that they can effectively shorten the route hops when processing a query request, lower system load and even can optimize the data distribution in system by combining with DHT model. In the end, there is a complete summary on the work of this paper and a discussion of future work.