Research On Some Issues For Congestion Control Mechanism Of Internet

In recent years, quite a number of researches attempt to extend architecture of Internet in order to support Quality of Service (QoS) for the forthcoming real multimedia applications. For example, IETF bring forward the Integrated Services model and the Differentiated Services successively. But whichever architecture we adopt finally, the core of technology needs to manage the traffic in proper level and granularity including Admission Control, Traffic Shaping, Queue Management, Scheduling and Congestion Control etc. In these technologies, Congestion Control should be the most essential and important problem. It is difficult to imagine that a network which is constantly suffered from serious congestions and can not be recovered in time is capable to achieve perfect QoS guarantee. It is to say that Congestion Control is the necessary precondition if we expect other QoS mechanisms to work in order.In this dissertation, by researching the problems of congestion control, we propose new mechanisms and algorithms to improve the performance of Internet. The main research works and results are listed as follows.1. Vegas+ and Vegas-AS are presented to solve the unnecessary throughput degradation of TCP Vegas when congestion occurs in the backward path or when rerouting occurs, respectively. Vegas+ estimates the available bandwidth of the forward path by a new forward path measurement. Vegas+ effectively improves the connection throughput and has a low complexity in implementation. Vegas-AS can solve the rerouting issue with TCP effectively by means of the Active Spurring Scheme and improve the connection throughput. In addition, Vegas-AS can be simply embedded into the TCP Vegas or enhanced TCP Vegas as an independent module with a low overhead.2. From the different angles, we research the Active Queue Management (AQM) scheme and present some new ideas and algorithms. Firstly, a novel estimation technology—dEWMA (double EWMA), which employs two EWMA filters cooperating each other to measure data , overcomes the defect that traditional EWMA estimation technology does not achieve fine agility and stability, and provides much more accurate , flexible data estimation. The effectiveness of...