Method and apparatus for priority control for cells in an output buffer type ATM switch

摘要

There is provided a method of performing priority control for cells in an output buffer type ATM switch including a switching unit, having a plurality of input ports and a plurality of output ports, for switching/outputting the cells input from the input ports to the output ports, and a plurality of output buffer units, connected to the output ports of the switching unit, for temporarily storing the cells output from the output ports to perform output control of the cells. A loss quality class and a delay quality class are added to each cell. A plurality of logical queues for temporarily storing the cells are vertically set in a buffer memory in accordance with the delay quality classes and routing information. The input cells are selectively written in the logical queues on the basis of the delay quality classes and the routing information added to the cells. A transition process is performed for all the logical queues to change the delay quality class of each of the logical queues into one of upper and lower classes depending on a cell storage amount in the logical queue. Upon completion of the transition process, the cells are read from the logical queue having the delay quality class which is a lowest class. IMAGE