Research On P2P Network And User Behaviors Modeling And Analysis Based On Measurement And Simulation

Recently,with the explosive increase of the access bandwidth and the new applications in Internet,as the tool for idle resource integration and reallocation, Peer-to-Peer technology influenced us very much not only in commercial and industries field,but also in the academic and social field.The new-born infrastructure intends to make full use of spare capacity(including the idle CPU cycles,disk spaces,and bandwidths, etc) of each PCs which have access to the Internet.By mutual cooperation and assistance,these PCs can break through the performance bottlenecks of traditional infrastructure and deal with the "mission impossible" which once faced by traditional Internet efficiently,reliably,and safely.At the same time,the surfers,who sit in front of these PCs,can establish the information exchange and resource sharing platform in the virtual world connected by all kinds of P2P applications.That is,these cold PCs can gradually gain some social property under the control of humans.Mastering the situation of various P2P applications,mining the behavior model of P2P users,understanding the network characteristics incurred by protocol implementation,discovering the security problems,they all contribute to improve the design principle and protocols of P2P systems.In addition,they will also provide the methodology for P2P flow monitoring and maintenance.In the thesis,based on the P2P datasets captured in Internet and simulation programs, we have done some research on two of the most popular P2P applications:file sharing systems and live media streaming systems.●By collecting the users profiles of BitTorrent,we retrieved and modeled the users behavior in the system.It's revealed there exist obvious flat-head phenomenon which is similar to "fetch-at-most-once" behaviors no matter for publishing and for downloading activities.We proposed the "Indirect Selection Principle" to explain the characteristics in users issuing behaviors.Furthermore,we also present the relationship between the file life span and the users' interests,and the sharing properties of users.●After developing our crawler,we traced and monitored most users of PPStream system in real time.Due to the rigid real-time requirements,the unique policies implemented in the system will definitely result in the unique characteristics of users.Based on the datasets,we tried to reveal users behaviors on geographical distribution,connection stability,users arrival/departure pattern,sharing and topology.It's proved the system pay fairness for efficiency. ●Because of the autonomous and social property of users,it's a vital concern how to design the incentive mechanisms to promote users share more in the system. Different mechanisms will incur the different organization patterns among users, and the topology varies consequently.By simulating the connection policies in BitTorrent and CoolStreaming Systems respectively,we tried to disclose some characteristics on topology of them.●In P2P live system,the buffer establishing and update paces will affect the sharng ratio of the whole system.From our measurement,we find out the "linear placement" mechanism adopted in PPLive System,and we think the strategy will influence the playback process directly.By rigid theoretic analysis,it's revealed the relationship between playback latency and some vital design parameters.By optimizing these parameters,the performance will be increased further.●Security problems is of vital importance in P2P systems.In the chunk-based live streaming systems,several notorious "polluters" will destroy the whole systems by inserting the fake chunks to the system.By utilizing the relationship among different data chunks,we propose a mesh-based mechanism to prevent the peers from polluted.The mechanism is lightweight and easy to be implemented.