Patent ID: 7027457

Claim:
A method for transferring data through a packet switch while providing differentiated Quality-of-Service (QoS) guarantees to respective traffic flows received at individual inputs of the packet switch, the method comprising the steps of: storing received data packets associated with said traffic flows in a respective input buffer wherein each respective input buffer resides in an ingress port card and is associated with a particular individual input of the packet switch; grouping said traffic flows within a respective input butter on at least a QoS guarantee basis; selecting stored data packets for transmission to a switch fabric according to a first plurality of schedulers, each scheduler in the first plurality of schedulers residing in said ingress port cards; assigning bandwidth to said selected data packets according to a second plurality of schedulers, each scheduler in the second plurality of schedulers residing in said ingress port cards; storing said selected data packets in a plurality of output buffers in said switch fabric, wherein the buffer capacity of the plurality of input buffers exceeds the buffer capacity of said plurality of output buffers; adapting the operation of at least one of said first and second schedulers in response to a determination that a utilization level of any output buffer has exceeded a threshold parameter; and choosing the data packets to be transmitted out of said plurality of output buffers according to a third plurality of schedulers, each scheduler of the third plurality of schedulers residing in said switch fabric.