Dynamics Modeling And Algorithms Of P2P Networks

With the development of information technology, many novel applications of computer networks have appeared. P2P is one of the most important applications. Although there were many models for P2P networks, few have addressed the model of dynamic behaviors. Meanwhile, P2P networks have a lot of problems, but modern control theory and system analysis methods provide a new perspective in solving these problems under existed application support environment. To this end, we study the dynamical modeling for P2P networks and some key algorithms. Then, we provide effective solutions and some advances for actual P2P networks.The main works and innovation are as follows:1. We propose a dynamical model for P2P file sharing systems and study some key algorithms. States of peers are defined as the amount of data which will be transmitted. We formulate a set of deterministic differential equations to describe the evolution of systems states by taking network physical characteristics (the physical upload, download bandwidth, storage space, etc) and software protocols (bandwidth allocation algorithm, peer selection algorithm, peer incentive mechanism, etc) into consideration. Then according to particular algorithms, we give the corresponding concrete models. Experiments show that the proposed model can adapt to different P2P file sharing systems. Therefore it provides a theoretical basis for designing high-performance P2P networks, improving existing P2P algorithms and researching stability of the P2P systems.2. We study the market mechanisms of economic principles and utilize it to model P2P file sharing systems. We name it as dynamic price-based incentive model (DPIM). Then, we study the incentive algorithm of DPIM. The results of simulation and analysis indicate the model can reduce free riding in P2P networks, punish cheating behaviors, and enhance file sharing efficiency and service quality.3. We study some key algorithms in the P2P-based Media Delivery Network (MDN). Based on the dynamical model of P2P, we define the states for the MDN and provide a novel dynamic model to character the behaviors of MDN systems. PN upload bandwidth, storage space, storage allocation algorithm, bandwidth allocation algorithm and PN selection algorithm are considered in the model. In order to improve the performance, some state-based algorithms are proposed. The results of simulation show that the model captures the characteristics of MDN in a more accurate way and provides a method for dynamic optimization of the system.