Research on Churn-resistance Mobile P2P Overlays
|School||Harbin Engineering University|
|Course||Applied Computer Technology|
|Keywords||Mobile P2P Overlays Data Dissemination Performance Evaluation Churn Optimization|
The demand for mobile peer-to-peer technology becomes much stronger because mobilenetworks are developed quickly, and mobile equipment and applications are more widely used.Mobile P2P overlays can shield the difference among the network routing protocols and themarks and addresses of physical equipment, and provide services for stable topology, loadbalance, and resources search etc. The structure of mobile P2P overlays directly determinesthe scalability, robust, security, and churn-resistance of the mobile P2P systems. Therefore theresearch of mobile P2P overlays is of great significance and application value. Although therehave been some mobile peer-to-peer overlays proposed, they get poor performance andchurn-resistance, which make them difficult to get practical application. Based on the existingresearch results, construction, evaluation, and optimization are intensively studied to solvesome problems in the research of mobile P2P overlays.By analyzing a variety of traditional peer-to-peer overlays with the basic principle andtopology structure, this thesis further expounds why the traditional P2P overlays can notcompletely adapt to the mobile networks. The concept of mobile P2P overlays is illustrated,and the existing mobile peer-to-peer overlays are analyzed and compared in detail. Thenetwork simulators are compared and chosen for the method validation and performanceevaluation of mobile P2P overlays.Firstly, the thesis proposes a mobile P2P overlay under the basis of the above mentionedresearch. The overlay constructs k-clique communities with different k value according to theorder of each node joining the overlay, uses contact nodes to link distinct k-cliquecommunities, and designs corresponding algorithms for joining, leaving and crashing of thenodes and construction of k-cliques. Meanwhile, it keeps adjusting the topology of the overlayby using topology control process and inter-clique connection processes to improveself-adaption for change of physical network topology and to increase the churn-resistanceability by combining data redundancy and proactive detection of failure nodes.Secondly, in order to realize the effective transmission of topology control informationand to maintain replica consistency of the node resource lists, the thesis researches on the datadissemination mechanism based on mobile P2P overlays. The appropriate data dissemination method is chosen according to the characteristics as resource-constrained nodes and linkinstability in mobile networks, and is improved based on the mobile P2P overlay topologystructure. By taking on the strategy as dynamic adjusting the dissemination probability ofnodes with different state, the dissemination probability of unstable nodes are added, whichmakes sure that the data can be disseminated to all the target nodes in a relatively short periodof time, the efficiency of data dissemination under churn is enhanced, and the network load iseffectively reduced.Thirdly, the performance evaluation model of mobile P2P overlays under churn isconstructed. Follow the model, performance of several overlays are evaluated under bothexponential churn model and KAD churn model. Furthermore, how to improve the existingchurn evaluation model based on frequency measurement is studied; by adding the indirectfactors influencing network churn, the improved churn evaluation model can more reallyreflect the actual network churn situation. By combination of simulation results andpolynomial fitting method, this thesis studies the parameter weights estimation method whichcan be used in any mobile P2P overlays.Lastly, parameters of mobile P2P overlays are optimized based on improved geneticalgorithm and automatic simulation to improve the performance of mobile peer-to-peeroverlays. In order to overcome the poor efficiency of the global optimization and classical"premature" phenomenon occurred in genetic algorithm, unnecessary crossover operations arereduced by computing the degree of similarity between individuals, and individuals with lowersimilarity degree get the greater probability of crossover operation between them. Automaticsimulation optimization is used to modify the simulator configuration file and the source codeand to compile and run automatically so as to improve the efficiency and reliability of theoptimization.Research of this thesis addresses the key technologies of mobile peer-to-peer network,which involves the network construction, data dissemination, performance evaluation andoptimization of network parameters, these researches lays a good theoretical basis andexperimental data base for future studies.