Ip Network Congestion Control

Internet is a packet-switched network .It is prone to congestion since neither the number of users nor their workloads are limited. In the past years ,a number of congestion control schemes have been proposed .Today, the congestion control used in Internet consists of two implementations :end point algorithm and link algorithm .Both of them are roughly studied in the thesis .We focus on the end-to-end congestion control in our research.TCP congestion control is the primary congestion control mechanisms used in nowadays Internet. Deeply studying TCP congestion control can not only improve the efficiency of network but also provide the reference and standard to other congestion control mechanisms. In this thesis, we study the basic algorithm of TCP congestion control including slow start , congestion avoidance , fast recovery and fast retransmit ,and then we introduce two TCP throughput models :simple model and complex model in detail.With the development of Internet, more and more real-time applications are applied. To fulfill their demands for communication, these applications are transported by UDP, which can bring the problem of unfairness and congestion collapse. To solve this problem, many TCP friendly congestion control mechanisms are proposed. We discuss a TCP throughput model based TCP-friendly congestion controlmechanism------TFRC, analyzing its basic theory, packet format, measurement of lossrate and sending rate adjustment. The simulation shows its better performance to real-time application over TCP as well as keeping the friendliness to TCP.The development of wireless communication and network brings new challenge on the congestion control research. Because of its unique characteristics such as fading, interferes, handoffs, etc, the cause of packet loss can not be narrowed down on the congestion. The traditional congestion control mechanism based on packet loss detection is not suitable for the reality of the current network environment. In this paper, we focus our research on the TCP congestion control and real-time application congestion control in wireless environment. New algorithms are proposed and analyzed.