This selects how this port schedules cell transmission across its different ATM QoS classes: strict fixed priority, where higher classes always transmit first, or weighted round-robin, where classes share bandwidth according to assigned weights. Fixed priority on this specific port guarantees the highest-priority traffic, like the high-priority rate queues 0-3, is never delayed by lower classes but risks starving low-priority traffic entirely during sustained congestion, while weighted round-robin trades some latency guarantee for fairer bandwidth sharing across all classes on this port. A port carrying both CBR voice and bulk data traffic might use fix-priority to guarantee the voice queues transmit first, whereas a port serving several equally-important data customers might use weighted-round-robin instead to prevent any one queue from monopolizing the link.