Patent ID: 7099355

Claim:
A method of scheduling the passage of data cells from N low-bandwidth data sources to M low-bandwidth data destinations in a data switching apparatus including ingress and egress multiplexers, N being the number of low-bandwidth data sources associated with each ingress multiplexer, in which the data switching apparatus includes: M/N ingress multiplexers, each arranged to receive data cells from a respective set of N said low-bandwidth data sources, M/N egress multiplexers, each arranged to transmit data cells to a respective set of N said low-bandwidth data destinations, a master control unit, and a central switch having M/N high-bandwidth input ports arranged to receive data cells from respective said ingress multiplexers, and M/N high-bandwidth output ports arranged to transmit data cells to respective said egress multiplexers, the central switch selectively interconnecting the input ports and output ports, under the direction of the master control unit, the method comprising the steps of: maintaining N input queues in each of said ingress multiplexers for queuing data cells received from the N respective said data sources, and maintaining M virtual output queues for queuing data cells directed to respective said data destinations; maintaining a respective ingress port table in each of said ingress multiplexers, each ingress port table having N×M entries, each entry corresponding to a respective combination of a said data source for that ingress port and a said data destination, transferring data cells from said input queues to said virtual output queues by each of said ingress multiplexers with a relative frequency according to a value of the corresponding entry of the ingress port table; maintaining a respective egress port table in each of said ingress multiplexers, the egress port table, having M entries, each entry corresponding to a respective said data destination, transferring data cells from said virtual output queues to said respective input ports of the central switch by each of said ingress multiplexers with a relative frequency according to the value of the corresponding entry of the egress port table; maintaining a central allocation table in the master control unit having (M/N) 2 entries, each corresponding to a respective combination of an input port and an output port, and controlling the central switch by the master control unit to interconnect pairs of said input ports and output ports with a relative frequency according to the value of the corresponding entry of the central allocation table; whereby said ingress port tables, egress port tables and central allocation table together determine the bandwidth through the digital data switching apparatus from each said data source to each said data destination.