Abstract: A system for controlling the flow of data cells through a packet switch combines both input and output buffers in a feedback loop. The fullness level of output buffers is continuously monitored and reported to an access device on the input side of the switch. The access device includes input buffers and a throttling device to stop the flow of data cells, and hold them in the input buffers, when the fullness level of the output buffers exceeds a predetermined level. A status message of output buffer fullness is compared to an access message indicating which output buffers are addressed by cells in the input buffers, and only those cells addressed to overfull output buffers are stopped by the throttling device. The efficiency of the packet switch is improved over switches using input buffers alone. The required capacity of the output buffers is reduced, thereby making it easier and less expensive to provide the required bandwidth.