| With the location efficiency of logarithmic level, good scalability and fault tolerance features, Chord can be a typical representative of the structured P2P network. It did not consider the network topology of the physical distance between nodes, so it's easy to form a overlay and physical layer topology mismatch and result in not only a lot of redundant transmission but also increased the response time. Therefore, the research of the match between overlay and physical topology is significant. In this paper, Chord topology and search algorithm is studied, as follows:First, we studied Chord network topologies and found that the problem is that the topology established on the overlay does not match the physical topology. Therefore, based on Chord, an improved model of topology TM-Chord is proposed. TM-Chord by directing each joining node to node physically proximity formed multiple groups of physical proximity. Each group is similar to Chord structure and through the links between nodes, logical ring is formed between groups.Secondly, we study Chord search algorithms, through the analysis of the existing algorithms and found that search is inefficient, and there exists redundant routing table entries. Therefore, based on the analysis of bi-directional search algorithm and index placement, based on TM-Chord, a group bi-directional search algorithm is proposed. In addition, at the process of updating pointer, adaptive change detection cycle and a simple method of updating redundancy are proposed.Finally, in order to verify the validity of the presented topology model and search algorithm, we did some simulation experiments. Generate a two-tier topology network by GT-ITM. One layer is used to simulate the physical network layer; another layer is used to simulate the proposed topology. This paper validated the TM-Chord topology and search algorithm in terms of topology matching degree, the average latency, average path length and network maintenance cost. |
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