ATM Networks Reactive Rongestion Control Algorithm Research

ATM is a typical high-speed network technology. ATM networks can effectively integrate all traffic types and services into a single network, such as voice, picture, and data. The technology of integration raises the utility of network resource. Because of the limit of network resource (link capacity, buffer length of network node) and the uncertain of traffic in networks, it should not be avoided that network congestion occurs, and congestion control becomes one of the key technologies in ATM networks.Based on a great lot of literatures, contribution of this paper includes:1. A novel congestion control method in ATM networks at the user network interface is proposed on basis of neural networks in this paper. In the proposed method, the controller takes the buffer length as congestion indication, takes sources quality and bandwidth utility as object function so as to learn on line. As the controller outputs, the coding rate for input traffic sources and the corresponding user percentage are used to adjust the cells' arrival rate to the multiplexer buffer. Compared with the previous method where cells' arrival rate is tuned only by the encoding rate and the encoding rates for all input traffic sources are regulated in a body, the proposed method guarantee that the quality of cells are optimal while cell loss rate is minimized, which means quality of service is guaranteed. Simulations show the effectiveness of the proposed methods.2. When there exists different round trip delay (RTD) for traffics with ABR service, ERICA recommended by ATM Forum will result in ACR's fluctuant adjustment. In the proposed flow control method for ABR service in ATM networks, by introduction of delay factors, the cell transmission rate for ABR traffic with different RTD are adjusted differently when the surplus bandwidth varies, and the rate variation amplitude for the short RTD traffic will be enlargeed while one for the long RTD traffic will be lessened, compared with ERICA. That is to say, when congestion occur, it is rapidly alleviated since the short RTD traffics reduce the transmission rate extensively and in time, and when redundant bandwidth occur, the link will be rapidly utilized since the short RTD traffic will get more bandwidth than gotten by fair share. Simulations for high speed ATM network and low speed ATM network show the proposed algorithm can reduce cell loss rate and depress the fluctuation of the cell transmission rate.