Study Of Congestion Control In High Speed Networks

With the rapid growth of next generation Internet backbone bandwidth and thenetwork data transmission demands of various new applications, the low efficiency ofthe TCP congestion control algorithm has gradually become the development bottle-neck in high speed networks. Therefore studying high speed transport protocols hasbecome a new hot spot in network research.In order to break through the inherent pattern in the majority of present conges-tion control research, i.e., heuristic algorithm design with simulation experimental ver-ification, this article, through the establishment and the consummation of a networktransport system model and with the aid of other mature theories such as control theoryand population evaluation theory, designs a specific congestion control mechanism andalgorithm for high speed networks and improves and gradually optimizes them. Theconcrete research contents and the conclusion are as follows:Based on a comprehensive summary of the newest research about congestion con-trol in high speed networks, this article establishes a general ?uid-?ow model to de-scribe the dynamics of a transport control system suitable for High Speed TCP, ScalableTCP and TCP, and obtains the linearization system model through the small-signal lin-earization method. Then this article derives the stability criterion of the system anddiscusses the in?uence of network parameters to the stability of system on the basis ofthe stability margin concept in control theory. The conclusion is as follows: the largerthe link bandwidth and the round trip time, the worse the stability degree of the system,and the larger the ?ow number in the network, the better the stability degree of system.With respect to designing a congestion control mechanism and algorithm for highspeed networks, this article establishes the direct and reasonable mapping relationshipbetween the objects of study in population ecology and the objects of study in networkcongestion control by analogy,and then successfully extends many classical popu-lation evolution models to the study of network congestion control. This article firsttakes efficiency and fairness as the goal, proposes one kind of rate evolution model andthe corresponding congestion control mechanism of explicit virtual load factor feed- back provided by the router, and implements the EVLF-TCP protocol which is highlyeffective, fair and robust. Then in order to further optimize the convergence and sta-bility of the congestion control algorithm in high speed networks, this article proposesthe coupling logistic evolution model and the corresponding congestion control mech-anism of explicit bandwidth pre-assignment provided by the router, and designs theCLTCP protocol with fast convergence and global asymptotic stability. At the sametime, theoretical analysis according to stability and convergence has been determined,and favorable performance of these two protocols has been confirmed through simula-tion.