| With the emergence of many new network applications and rapid expansion of the user, Internet traffic has been increasing dramatically, and the network congestion appears to be a more and more critical issue. Congestion control mechanisms are very important in guaranteeing the stability of Internet. Moreover, a suitibale congestion control mechanism becomes the necessary premise for other QoS (Quality of Service) mechanism to work effectively.TCP is the dominant transport protocol on Internet, and the current stability of Internet depends on its end-to-end congestion control, which uses an AIMD (Additive Increase Multiplicative Decrease) algorithm. Although TCP congestion control is appropriate for applications such as bulk data transfer, it is not suitable for real-time applications. In order to support the-transfer of real-time application such as streaming multimedia, various TCP-Friendly congestion control mechanisms have been proposed. In this thesis, some of these mechanisms are described, and the performance of them are compared and analyzed through simulation.Congestion control mechanisms based on end point are easy to be implemented, but a problem with them is that the congestion is detected through the effects of congestion rather than the congestion itself. And also there are problems with fairness and non-compaliant sources. Therefore, it seems logical to palce the congestion control mechanism at the location of congestion, i.e, the router. Two typical schemes, that is, AQM (Active Queue Management) and ECN (Explicit Congestion Notification), are introduced in the thesis. The performance of some typical AQM algorithms is also analyzed through simulation.Another problem with TCP's congestion mechanism is that it is difficult to achieve fair bandwidth sharing among various competing connections. Currently three approchs are used to achieve fair bandwith sharing, that is, per-flow scheduling algorithm, per-flow dropping algorithm and stateless fair...
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