Switch Source End System Forward RM Cell Backward RM Cell Data Cell Switch Destination End System

The Available Bit Rate ABR service that is being standardized by the ATM Forum dynamically deter mines the maximum transmission rate the explicit rate of a connection A drawback of the dynamic control scheme for calculating the explicit rates is that it tries to allocate the same bandwidth to all ABR connections regardless of the application type of the connection In this study a multi level explicit rate scheme is proposed that can allocate di erent transmission rates bounds to connections ABR tra c is controlled at three levels At the topmost level bandwidth is dynamically regulated be tween CBR VBR and ABR tra c sources At the next level bandwidth is controlled between di erent classes of ABR tra c At the lowest level bandwidth is dis tributed among connections belonging to the same ABR tra c class The e ectiveness of the proposed scheme is demonstrated in simulation experiments