Research And Design Of Chord Protocol Based On Topology-matching

Structured P2P algorithm adopts DHT(distributed hash table)technology , forming Overlay Network by mapping each node to one nodeID . And, it provides scalable and robust resource localization and routing service by mapping resource keywords to the nodes of the overlay network. Because of the simplicity of Chord protocol, also under the condition that many nodes dynamically join in and leave , its stable algorithm maintains well seeking efficiency . The DHT based resource localization algorithms, which include Chord protocol, therefore are widely researched by people.Since Chord protocol hasn't considered the topology information of underly network, the overlay network and underly network of Chord protocol have the problem of topology mismatching. consequently the efficiency of Chord protocol is influenced.While downloading datas,transmitting datas by selecting nodes randomly leads to such consequences: datas traffic flow disorder in the process of datas transmission, datas traffic flow increase of backbone links, and the utilization reduction of networks resource.On the basis of meticulous research on Chord protocol, this paper takes the topology mismatch and traffic flow optimizing problems of Chord protocol as the priority of research. The key to the solution of these problems is how to acquire topology information,and how to utilize the topology information. this paper analyzes present situation of research concerning the topology mismatch and traffic flow optimizing P2P networks . Taking P4P that is widely researched as the break through point, this paper has resolved the problem of topology acquisition. Utilizing the space accumulating attribute of Hilbert curve, we applied Hilbert transformation to networks topology information to generate correspondent Hilbert coding, about nodes joining algorithms, T-Chord protocol has resolved the topology mismatching problem by utilizing the Hilbert coding and hash value of nodes to generate nodeID, T-Chord protocol sorts resource index information according to hilbert coding of resource nodes. While selecting resource nodes,T-Chord protocol selects resource nodes that have Hilbert coding similar to that of resource requesting nodes. Therefore, T-Chord protocol has acquired the aim of flow optimizing by avoiding datas flow disorder caused by nodes randomness.There are several points below about the design of T-Chord。(1) The acquisition of topology information, acquiring network topology information with the utilization of p4p technology. Using Hilbert coding to process network topology information,this paper transforms multidimensional datas to one-dimensional datas.(2)We has improved the nodes joining algorithm of Chord protocol. In the process of establishing Chord networks,we has refered to the topology information of nodes to establish topology matching Chord network.(3)We has improved the organization rule of resource index information in Chord protocol .Instaed of depositing disorderly, we deposit the resource index information according to the site order of underlay network.(4)We have improved the strategy of node selection in the case of using Chord protocol to download datas. In the process of nodes selection , we has refered to the network topology information of nodes, taking precedence to select the near nodes that is on the underlay network, so as to reduce data traffic flow among networks and time delay of data transmission.On the aspects of average routing delay, average data transmission time and data traffic flow among networks, this paper has made simulation experiments on T-Chord and Chord protocols with the simulation device of Oversim. Also, after contrastive analysis of the experiments results,we have verified the effectiveness of T-Chord protocol。...