| Summary: | 碩士 === 國立臺灣大學 === 電機工程學研究所 === 92 === System design and performance analysis of Transmission Control Protocol with Active Queue Management
Student: Chun-Wei Li Advisor: Feng-Li Lian
Department of Electrical Engineering
National Taiwan University
ABSTRACT
In this thesis, we first introduce current networks architecture and briefly explain the functions of each network layer. We mainly focus on the transport layer of the ISO/OSI seven layers. We list some important TCP algorithms such as TCP-Reno and AQM algorithms such as the RED algorithm. We look into the nonlinear dynamics in a discrete-time network model combined with Reno and RED. The system is regarded as the deterministic closed-loop system. We investigate its stability regions. First, we use linearized error dynamical vector-matrix model to present the nonlinear systems and discuss its feedback properties in terms of network parameters such as link capacity, number of senders, and round trip time.
Second, we use the z-transform to transform the derived dynamical equations into the transfer function format. Thus, we can investigate the stability of the system by plotting Bode plot or Nichols chart of the transfer function and use the characteristic equation to find the poles of the system. Based on the location of the poles we can observe the parameter effects on the system performance. Besides, the pole location effects are also discussed by observing the damping ratio and natural frequency of the system. We also change the initial conditions to observe the difference in the normal case.
Finally we investigate the equilibrium condition variations when the parameters are changed and the system performance on RED and network parameters are changed. We present NS-2 simulations to support our analysis.
Key words: TCP congestion control, AQM, control theory, nonlinear analysis
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