| With the development of science and technology, Internet is more and more widely used in our daily life. Multimedia, e-commerce and other elements of our life have also entered this big platform. When people enjoy the network life through this platform, there must be a lot of data interaction and transmission in the network, and this will bring a heavy burden on the computer networks. Thus, in order to meet the needs of high-speed growth of data transmition, the topic on how to ensure the satisfactory quality of network service has become a common concern. Available bandwidth, being one of the most important indexes, is the reflection of network operation status and performance. It can provide us with reliable basis and help in planning the network layout, monitoring the current status of network operations, optimizing network performance, improving network transmission efficiency, etc. How to measure the available bandwidth of the current path accurately and efficiently has become the main problem that various domestic and international network research and measurement institutions have researched and made great effort to overcome in recent years.This thesis focuses on the method of available bandwidth measurement, studies and analyzes the performance of available bandwidth measurement techniques. The application environment of each type of measurement technology is discussed after conducting simulation experiments. With an aim of understanding the current states of network accurately and efficiently, we can use the result of measurement to improve the quality of current network service. Several representative algorithms are selected to research and discussion, such as, pathload, IGI/PTR, SPRUCE, pathChirp, Yaz and ASSOLO. Based on the analysis and research on these algorithms, the author of the thesis realizes the code of the algorithms, simulate real network environment and finish the simulation experiment on the NS2 platform. By collecting the results and the parameters of the experiments, the author of the thesis has analyzed and made comparison of some factors of every algorithm, such as, accuracy, error rate, stability, measurement time and the impact on the existing network conditions. Then the advantages, disadvantages and the most appropriate network environment of each method are summrized.Finally, this thesis puts forward a new scheme of available bandwidth bottleneck location, which is called STABBA. STABBA, based on STAB, is a bottleneck link location tool to measure the available bandwidth. We use the detection packet queue of ASSOLO to improve the STAB. The new scheme can in a certain extent reduce the number of probe packets and improve the accuracy of the available bandwidth measurement. |
