Toward a Time - Scale Based Framework for ABR Tra c Management

This paper discusses a number of issues and possibilities for more eeective ABR (Available Bit Rate) traac management which arise from a careful consideration of various time scales present in an ATM networking environment. Since the ABR applications use the remaining resources after CBR (Constant Bit Rate) and VBR (Variable Bit Rate) applications have been accommodated, the ABR rate should be controlled through a feedback based ow control scheme to avoid excessive losses. It is well known that the increased propagation delay increases the amount of bandwidth mismatch which may induce cell losses. For this reason, the eeectiveness of feedback based ow control schemes reduce with increased propagation delay. But, besides the propagation delay, some other system parameters (network, ABR and VBR time scales) may also have considerable eeects on the feedback based ow control schemes. In this paper by considering a tractable analytical model, the impact of these time scales is considered. Also, a proactive feedback based ow control scheme which aims to reduce the amount of bandwidth mismatch by generating early feedbacks is introduced.