SMC Networks 10/100 manual Priority Commands, 146

COMMAND LINE INTERFACE

Priority Commands

Class of Service (CoS) allows data packets that have greater precedence to receive higher service priority when traffic is buffered in the switch due to congestion. This switch supports CoS with four priority queues for each port. Data packets in a port’s high-priority queues will be transmitted before those in the lower-priority queues.

You can set the switch to service the queues based on a strict rule that requires all traffic in a higher priority queue to be processed before lower priority queues are serviced, or use Weighted Round-Robin (WRR) queuing that specifies a relative weight of each queue. WRR uses a predefined relative weight for each queue that determines the percentage of service time the switch services each queue before moving on to the next queue. This prevents the head-of-line blocking that can occur with strict priority queuing.

Inbound frames that do not have VLAN tags are tagged with a default service priority of zero, and placed in queue 1 at the output port. Therefore, any inbound frames that do not have priority tags will be placed in queue 1 of the output port. (Note that if the output port is an untagged member of the associated VLAN, these frames are stripped of all VLAN tags prior to transmission.) However, if the incoming frame is an IEEE 802.1Q VLAN tagged frame, the IEEE 802.1p User Priority bits will be used.

Command	Function	Mode	Page
queue mode	Sets the queue mode to strict priority or	GC	3-147
	Weighted Round-Robin (WRR)
show queue mode	Shows the current queue mode	NE,	3-147
		PE

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