Research On Key Technology In P2P Overlay Network

Building an overlay based on the physical Netwok is one of the most popular technologies in P2P system. There are two types of P2P systems respectively called structured and unstructured P2P system. The locating algorithms in structured systems fail to adapt the dynamic joining and leaving of nodes. Because the specific name and key words are necessary for locating object and result in the absence of adaptability and fault-tolerant. Unstructured systems are suitable to the heterogeneous environment in really Network. But the message flooding generates large-scale querying flows to limit the scalability and efficiency. Supernode-based overlay can cope with the above problems. Not only does it have efficiency of the centralized search but also use the distributed search method to attain the autonomic nature and the adaptability to the dynamic environment.The paper analyses in detail and compares the characteristic and typical system of different topology structure in P2P overlay Network. The principle, advantage and disadvantage of the suoernode-based P2P overlay are specially discussed in the paper. A supernode selection mechanism based on information exchange (SSBIE) is proposed aiming at the problems in supernode-based P2P overlay. And the P2P overlay topology characteristic and the search performance are analysed by some simulations. The main achievements obtained are presented below:(1) A partition of AS based on the cooperating of typical topology and geography is presented accounting for the unmatching topology in supernode-based P2P overlay. It forms into the AS by the physical distance.The closed nodes in physical group a AS, and the closed ASes in physical are adjoining each other. Selecting node within each AS as the own supernode guarantees the matching between the physical Network and ovelay.(2) Aiming at the unreasonable supernode selection and free-riding problems, supernode selection based on information exchange(SSBIE) is presented in paper considering delay, physical distance, information exchange frequency, information exchange time and degree of content similarity. SSBIE selects the supernode and identifyes the free-riding nodes by each node's score. The experimental results show that the SSBIE improves the file querying success rate, decreases the average querying hops and querying delay in supernode-based P2P overlay.(3) A three information centre mechanism is proposed to solve single node-failture instead of the the traditinal supernode redundancy which attains reliability by using more cost of system. It receives more reliability but not brings more cost of system.(4) The paper concludes that the the performance of searching algorithm is affected on the topology structure of P2P overlay by implementing flooding search strategy in different topology. The experimental results show that the three information centre overlay has better performance.