Chapter 18 Queuing Method; Introduction To Queuing; Strictly Priority; Weighted Fair Scheduling - ZyXEL Communications Dimension ES-3124 User Manual

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.
18.1.1

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.
18.1.2

Weighted Fair Scheduling

Weighted Fair Scheduling is used to guarantee each queue's minimum bandwidth based on their bandwidth weight
(portion) (the number you configure in the Weight field – see Figure 18-1) when there is traffic congestion. WFS 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:
For example, using the default setting, Q0 on Port 1 gets a guaranteed bandwidth of:

18.2 Configuring Queuing

Click Queuing Method under Advanced Application in the navigation panel.
Queuing Method
This chapter introduces SP (Strictly Priority) and WFS (Weighted Fair Scheduling).
Queue Weight
Total Queue Weight
1
x 100 Mbps = 3 Mbps
1+2+3+4+5+6+7+8
x Port Speed
Dimension ES-3124 Ethernet Switch
Chapter 18
Queuing Method
18-1