Method and system for guaranteeing quality of service in large capacity input output buffered cell switch based on minimum bandwidth guarantees and weighted fair share of unused bandwidth

摘要

Data cells of plural classes are transferred from input ports to output ports through a switch by storing the cells at each input port in class-specific virtual output queues (VOQ) within sets of VOQs associated with output ports, and providing credits to VOQs according to class-associated guaranteed bandwidths. When a cell is received at a VOQ having credits, a high-priority request for transfer is generated. If a cell is received at a VOQ that does not have any available credits, a low-priority request for transfer is generated. In response to requests, grants are issued to VOQ sets without regard to class, high-priority requests being favored over low-priority requests. When a grant is received for a particular VOQ set, an arbitrator selects a VOQ from the set, giving priority to VOQs having credits over VOQs without credits, and a cell from the selected VOQ is transferred. Requests generated from all input ports are forwarded to a central scheduler associated with a switch fabric slice, the central scheduler issuing the grants. The switch fabric may comprise multiple slices and a central scheduler, across which requests may be distributed in parallel, for example, the switch fabric slices being selected in a fixed order. While all high-priority requests are granted, low priority requests may be granted by the central scheduler according to a weighted fair share policy.