Abstract: Disclosed is an apparatus and method of monitoring the queue state of a switch in the subscriber board of an asynchronous transfer mode switching system. A difference value between the present time value and a previous input time value stored in a memory per connection is inputted to a forward resource management (FRM) cell when a resource management (RM) cell is inputted from a source, and a switch load measurement value written in the FRM cell is obtained by calculating the difference value between the present time value and a previous output time value stored in the memory per connection when the FRM cell transmitted from the source passes through the switch. The obtained switch load measurement value is inputted to a backward resource management (BRM) cell transmitted from a destination to be transmitted to the switch.

Abstract: A method of transmitting a cell between the ATM layer and the physical layer is provided for the ATM matching system, which includes the physical layer divided into a specified number of uniform physical device groups multiplexly polled by the ATM layer. The method comprises the steps of multiplexly polling the physical device groups by the ATM layer, transmitting an enable signal to the polled device upon receipt of a state signal from the physical layer, transmitting the cell to the physical layer, checking the multiplexed polling of the ATM layer by the physical layer, writing a physical port number into the cell with transmitting a state signal to the ATM layer upon receipt of the multiplexed polling, and transmitting the cell to the ATM layer upon receipt of an enable signal from the ATM layer.