Available Bit Rate (ABR) Flow Control In Asynchronous Transfer Mode (ATM) Networks

Available Bit Rate (ABR) flow control is an effective measure in ATM network congestion control and traffic management. In high-speed ATM networks,the switch performance lies on the algorithm simplicity in some degree. Although the simplicity of binary flow control is very attractive,the queue length and allowed cell rate (ACR) controlled by the standard EFCI algorithm oscillate with great amplitude,which must have negative impact on the performance,so its applicability was doubted. Considering that the intuition-based heuristic algorithm has blindness and one-sidedness,based on the modern control theory,through simulation experiments,the flow control of ATM networks is studied deeply in this paper and some achievements are reached.The binary ABR flow control model is firstly deduced. Subsequently,the nonlinear model is locally linearized about equilibrium point,thus,the linear model is obtained. With this model,the performance of standard EFCI algorithm is evaluated and the conclusion is that oscillations are caused by the nonlinear component existed in EFCI algorithm. Thus,EFCI algorithm is improved and the oscillation is overcome validly.And further,a linear PID controller is designed to replace the nonlinear component in the standard EFCI algorithm,it makes flow control system more robust,at same time,controls the queue length to expected value,which is beneficial to decrease delay in queue.Because the network status is changeable in practice,in order to enhance the ability against disturbance and noise,a novel binary ABR flow control algorithm is put forward using the sliding mode variable structure controller. The simulation results show that new algorithms avoid the self-oscillation induced by the nonlinear component in the standard EFCIalgorithm.Finally,the transmission performance of TCP/IP over ATM is investigated through simulation experiments,and the valuable conclusion and constructive suggestions are drawn.