Research Of Effective Resource Discovery Algorithm In Hybrid P2P Network Model

P2P (Peer to Peer) network model, with low deployment costs and abundant resources, is more and more popular on the internet. In P2P network, all resources are stored dispersedly in the users' computers (peers), and shared among peers without the intervention of servers. Thus, the resource discovery algorithm is the core of the P2P network. The existing resource discovery algorithms can be divided into three categories:Directory mechanism in centralized directory-based P2P, Flooding mechanism in unstructured P2P and DHT based mechanism in structured P2P. However, all of them have some shortages which restricted the large-scale development of P2P. Directory mechanism have not laid server aside completely, so it remains some shortages of Client/Server model, such as the bottlenecks of the server. Flooding mechanism is inefficiencies because it generates a lot of redundancy traffic. DHT mechanism does not consider the physical information of the peers during the mapping physical topology to logical topology, so the physical topology and logical topology are mismatched. On the other hand, the resource discovery algorithms are complicated in structural P2P, so its scalability is so limited. The meaning of this paper is to propose a new resource discovery algorithm to improve the efficiency of resource discovery and the scalability of P2P networks.In this paper, by analyzing and studying various existing P2P resource discovery algorithms, the author summarized advantages and disadvantages of these algorithms and then proposes a resource discovery algorithm based on hybrid structured P2P networks-Lerd (Location-aware Effective Resource Discovery). The core idea of the algorithm is that, by considering the performance, stability, and other indicators of peers, all peers are divided into two levels:super peers and normal peers. In accordance with physical location, divide the whole network into several domains and then allocate the corresponding regional identifier to each domain. Each domain is managed by a super peer. When a new peer wants to join the network, it will use the physical location-aware technique to calculate its physical location, and then choose the nearest domain to join. Thus the topology mismatch problem can be resolved. We mix domain information into both of the node and the resource identifier, so that we can use this domain information to locate the resource during the resource discovery. By using this mechanism, we can limit the complex of the resource discover algorithm as a constant, O (1). To verify the algorithm, NS2 (Network Simulator 2) is used. Firstly, code this new algorithm by using C++. Secondly, add it into the protocol library of NS2 and compile NS2. Finally, a series of simulation is taken in different scale of network.In this paper, hops and time delay in resource discovery message routing are used as metric to analyze the simulation result. We compare the result with Flooding and Chord algorithm, which is the typical algorithm of unstructured P2P and structured P2P respectively. The analyze result show that the hops and time delay of Lerd is markedly lower than Flooding and Chord while the scale of network is growing. The hops of the resource discovery are limited as a constant between 4 and 6. The time delay is increasing slowly. As a result, Lerd algorithm achieves the aim of improving the efficiency of resource discovery and network scalability.