In one embodiment, a packet-based system having a number of buses is stimulated using apparatus having 1) a hardware interface configured to provide data packets to the buses; 2) a plurality of hardware-based queue schedulers, each configured to schedule data packets received from a respective one of a plurality of data packet sources, in a respective one of a plurality of hardware-based queues; and 3) a hardware-based priority scheduler configured to cause each particular queue to transmit a next highest priority data packet over one of the buses, based on i) timing requirements of the next highest priority data packet in the particular queue, and ii) a determination that transmission of the next highest priority data packet in the particular queue will not delay a transmission of a higher priority data packet in another one of the hardware-based queues.