Queue measurement apparatus and methodology

Abstract

A queue length measurement device that is comprised of a number of queues that are capable of holding data cells. A differential counter is coupled to each queue. The counter is incremented when a cell is written into the queue and decremented when a cell is read from the queue. An interval measurement device is coupled to the differential counter. The interval measurement device generates a pulse to reset the counter at fixed intervals equivalent to n cells time (where n is the maximum number of cells the queue counter can measure). A multiplexer is coupled to the multiple differential counters. A transfer control circuit coupled to the interval measurement device selects the appropriate queue length to be output from the multiplexer to the other switch elements. A system and methodology are also provided to provide for queue flow statistics and closed loop control of cell flow into the queue. A queue measurement apparatus is provided for measuring a data queue size. The apparatus is comprised of a queue, an interval measurement device and differential queue length logic. The queue is capable of holding a plurality of data cells. The interval measurement device generates a pulse at predetermined intervals. The differential queue length generation logic is coupled to the queue and the interval measurement device, and generates a queue size output representative of the measurement of the change in queue size during the predefined interval. The queue size output represents the difference between a present and a previous queue length.