Research On Next Generation Internet Congestion Control Strategy

With the rapid development of Internet size and the explosive increase of the number of users, the new various network applications appear almost every day. Although the network bandwidth increases under Moore rule, it never meets the bandwidth resources requirement of people. Congestion control problem in the new networks environment continues to be the hotspot in the researcher circles. At the same time, more and more users and various applications lead to that traffic increases doubly in the Internet, which makes network congestion frequent. Moreover multiform bad even malice flux behaviors make it more serious. It is difficult for TCP congestion control mechanism to meet the network requirement. So it is imperative to research new congestion control theory and method. The goal of congestion control is to make full use of the network resources effectively and fairly, and to improve the network integrated performance and quality of service. So, the network congestion control is the main way to improve the network performance and reform the quality of service. And the research about network congestion control problem has also been a current hot subject in both computer network and control theory, which makes great sense in theory as well as a wide range of practical application.The main research works and results are listed as follows:1,To the problem of analytic model of the TCP congestion control protocol, using the fluid-flow approximation which we simulate the dynamic behavior of the Reno congestion controller. By means of the theory of function differential equation, we analyze the local Robustness of this model and derive a sufficient Robustness condition. The result indicates that Reno algorithm in the Internet today becomes unstable when delay increases, or when link capacity increases. The instability of Reno makes it unsuitable for high-speed large capacity of Next Generation Internet (NGI), which is inherent. The simulation results coincide with the theoretical results, which demonstrated by the well-known ns-2 simulator.2,Based on the cyclical model for the steady state behavior of the source algorithm, the limits of Vegas are analysis in detail. A new adaptive mechanism for Vegas called the F-Vegas (Fairness-Vegas) algorithm was designed, which can solve the continuous decline in throughput by rerouting. Simulation show that the F-Vegas is able to obtain a fairer share of the network bandwidth when competing with other TCP flows such as Reno. The performance and fairness of the designed algorithm are verified using NS simulations.3,E-Vegas is presented to solve the unnecessary throughput deterioration of Vegas when congestion occurs in the backward path. E-Vegas estimates the available bandwidth of the forward path by a new forward path measurement. The E-Vegas can effectively improve the connection throughput and greatly reduces the complexity of the implementation of the algorithm.4,From the perspective of protocol design, the paper reach the conclusions that TFRC is unsuitable for the MANET environment. According to the problem of TFRC, an enhancement for TFRC called Vegas Virtual TFRC was present. Unlike TFRC, it estimates the congestion by implicit Vegas detection strategy and notifies the congestion by Virtual Loss Packet Notification (VLPN). The two techniques preferably overcome the defects of TFRC, shield the effect of non-congestion packet loss on the connection throughput to a large extent, and improve the performance of TFRC in the MANET.