ZyXEL ES-4124 User Guide - Page 167
Queuing Method
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CHAPTER 20 Queuing Method This chapter introduces the queuing methods supported. 20.1 Queuing Method Overview 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. Queuing algorithms allow switches to maintain separate queues for packets from each individual source or flow and prevent a source from monopolizing the bandwidth. 20.1.1 Strictly Priority Strictly Priority (SP) 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. 20.1.2 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 - see Figure 18 1) 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 bandwidth is calculated as follows: Queue Weight x Port Speed Total Queue Weight For example, using the default setting, Q0 on Port 1 gets a guaranteed bandwidth of: 1 1+2+3+4+5+6+7+8 x 100 Mbps = 3 Mbps ES-4124 User's Guide 167