Internet is a global networking system which ensures a continuity between computer systems and equipment on a large scale. Internet is growing not only in the terms of connection but also diversity of the application layers. Therefore, Internet congestion is inevitable. In order that transmission lines may be smooth, congestion control at the network nodes plays a very important role for the Internet operational efficiency and reliability for users. To study and improve congestion control mechanism at the network nodes, the introduction of the thesis comes from general research of domestic and international control situation of congestion at the network nodes in order to show the scientific and necessary nature of the thesis. Thence, the thesis may set out the study motivation and study goals. Next, the thesis has proposed study methodology and study subjects, in order to perform the study goals and finally the introduction presents the layout and contributions of the thesis.