ZyXEL Communications Dimension ES-3024, User Manual, Page: 136 / 212

Dimension ES-3024 Ethernet Switch
Queuing Method 18-1
Chapter 18
Queuing Method
This chapter introduces SPQ and WFQ.
18.1 Introduction to Queuing
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.
The switch has four physical queues, Q0 to Q3. Q3 has the highest priority and Q0 has the lowest.
Table 18-1 Physical Queue Priority
QUEUE PRIORITY
Q3 1 (Highest)
Q2 2
Q1 3
Q0 4 (Lowest)
18.1.1 Strict Priority Queuing (SPQ)
Strict Priority Queuing (SPQ) services queues based on priority only. As traffic comes into the switch, traffic on the
highest priority queue, Q3 is transmitted first. When that queue empties, traffic on the next highest-priority queue,
Q2 is transmitted until Q2 empties, and then traffic is transmitted on Q1 and so on. If higher priority queues never
empty, then traffic on lower priority queues never gets sent. SPQ does not automatically adapt to changing network
requirements.
18.1.2 Weighted Fair Queuing (WFQ)
Weighted Fair Queuing (WFQ) services queues based on their priority and queue weight (the number you configure
in the
% field – see Figure 18-1 ). WFQ is activated only when a port has more traffic than it can handle. Queues
with larger weights get more service than queues with smaller weights. This queuing mechanism is highly efficient
in that it divides any available bandwidth across the different traffic queues.
18.2 Configuring Queuing
Click Queuing Method under Advanced Application in the navigation panel.