A network device for processing data includes at least one ingress module for performing switching functions on incoming data, a memory management unit for storing the incoming data and at least one egress module for transmitting the incoming data to at least one egress port. The at least one ingress module is configured to determine a priority for the incoming data, where that priority is mapped to a discrete number of priority groups and where the priority groups are determined on a per-port basis and provide guaranteed delivery or best throughput, and flow of data through the network device is controlled on a basis of at least one of the priority groups and assigned priorities.