Adaptive P-Persistent CSMA/CD And Computer Simulation Research

Internet users and applications grow rapidly with development of Internet scale. Computer network congestion becomes an important problem. A great deal of research had been developed in network congestion control recent years. Congestion control algorithms have two main parts. One is source algorithm on end system, and another is link algorithm on network's equipments. Network congestion is due to unbalance distribution of network resources and network flow. Congestion cannot be eliminated by enhancing network process ability. The design of congestion control algorithm becomes very difficult because of its distribution, network complexity and performance requirement of the algorithm. The congestion problems have not been solved up to date. The throughput decrease or even entire block of any network's node and link can all be called congestion generally. Here we introduce a majority of content about computer network congestion control. We stress on the problem of local area computer network's sharing media access, and bring forward the resolve for Ethernet of the special congestion of throughput decrease greatly at heavy loads. Anymore, we study on how to reduce Ethernet frame delay and access time uncertainty about real time communication. The main content in our paper include:The first chapter introduces basic conception about computer network congestion control.We point out a new better resolution, adaptive p-persistent CSMA/CD media access policy, for Ethernet after introducing its default in the second chapter. The commercialized local area networks media access control protocol IEEE 802.3 is 1-persistant CSMA/CD, which leads distinctly poor performance under heavy loads in the same collision domain. This paper analyzed p-persistent CSMA/CD protocol and proposed a new adaptive algorithm for the adjustment of the coefficient p by real-time channel traffic sensing based on the feedback control theory, i.e., changing the value of p dynamically through the analysis of networks' flow to control the behavior of the stations sending data frames in the same collision domain, to keep the media channel in an optimal state and to enhance the channel transmission efficiency. We improve the adaptive p-persistent CSMA/CD to make it suitable for real-time communication considering the rapid grown of real-time applications such as flow media. Here we call the method as competition time lengthened adaptive p-persistent CSMA/CD. This protocol gives real-time communication a higher priority to access channel and reduce Ethernet delay time uncertainty greatly.The third chapter is a simulation part. In this chapter we compare adaptive p-persistent CSMA/CD simulation results to 802.3 Ethernet. We also compare the detailed performance with the two protocols in different statistic period, node number, packets size and packet interval. The conclusion show adaptive p-persistent having a better performance. The contention time lengthened real-time p-persistent simulation results show not only real-time traffic delay performance being enhanced greatly but also common data delay and throughputs not being affected evidently.