ZyXEL GS2200-8 User Guide - Page 165
Queuing Method
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CHAPTER 22 Queuing Method 22.1 Overview This chapter introduces the queuing methods supported. Queuing is used to help solve performance degradation when there is network congestion. Use the Queuing Method screen to configure queuing algorithms for outgoing traffic. See also Priority Queue Assignment in Switch Setup and 802.1p Priority in Port Setup for related information. 22.1.1 What You Can Do Use the Queueing Method screen (Section 22.2 on page 166) set priorities for the queues of the Switch. This distributes bandwidth across the different traffic queues. 22.1.2 What You Need to Know Queuing algorithms allow switches to maintain separate queues for packets from each individual source or flow and prevent a source from monopolizing the bandwidth. Strictly Priority Queuing Strictly Priority Queuing (SPQ) services queues based on priority only. As traffic comes into the Switch, traffic on the highest priority queue, Q7 is transmitted first. When that queue empties, traffic on the next highest-priority queue, Q6 is transmitted until Q6 empties, and then traffic is transmitted on Q5 and so on. If higher priority queues never empty, then traffic on lower priority queues never gets sent. SP does not automatically adapt to changing network requirements. Weighted Fair Queuing Weighted Fair Queuing is used to guarantee each queue's minimum bandwidth based on its bandwidth weight (portion) (the number you configure in the Weight field) when there is traffic congestion. WFQ is activated only when a port has more traffic than it can handle. Queues with larger weights get more guaranteed bandwidth than queues with smaller weights. This queuing mechanism is highly efficient in that it divides any available bandwidth across the different traffic queues. By default, the weight for Q0 is 1, for Q1 is 2, for Q2 is 3, and so on. Guaranteed quantum is calculated as Queue Weight x 2048 bytes. Weighted Round Robin Scheduling (WRR) Round Robin Scheduling services queues on a rotating basis and is activated only when a port has more traffic than it can handle. A queue is a given an amount of bandwidth irrespective of the incoming traffic on that port. This queue then moves to the back of the list. The next queue is given GS2200-8/24 User's Guide 165