Queuing Method. ZyXEL Communications VES-1616F-3X, VES-1616F-3x Series

C H A P T E R 17

Queuing Method

This chapter introduces the queuing methods supported.

17.1 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.

Q3

Q2

Q1

Q0

Q7

Q6

Q5

Q4

The switch has eight physical queues, Q0 to Q7. Q7 has the highest priority and Q0 has the lowest.

Table 38 Physical Queue Priority

QUEUE PRIORITY

6

5

8 (Highest)

7

4

3

2

1 (Lowest)

17.1.1 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.

123

VES-1616F-3x Series User’s Guide

Chapter 17 Queuing Method

17.1.2 Weighted Fair Scheduling (WFS)

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) 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:

Guaranteed bandwidth = Queue Weight ÷ Total Queue Weight x Port Speed

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

17.2 Configuring Queuing

Click Advanced Application > Queuing Method in the navigation panel.

Figure 49 Queuing Method

124

VES-1616F-3x Series User’s Guide

Chapter 17 Queuing Method

The following table describes the labels in this screen.

Table 39 Queuing Method

LABEL DESCRIPTION

FE Port SPQ

Enable

Strictly Priority services queues based on priority only. When the highest priority queue empties, traffic on the next highest-priority queue begins. Q7 has the highest priority and Q0 the lowest.

Weighted Fair Scheduling is used to guarantee each queue's minimum bandwidth based on their bandwidth portion (weight) (the number you configure in the Weight field). Queues with larger weights get more guaranteed bandwidth than queues with smaller weights.

This field is applicable only when you select Weighted Fair Scheduling.

Select a queue (Q0 to Q7) to have the switch use Strictly Priority to service the subsequent queue(s) after and including the specified queue for the 10/100 Mbps

Ethernet ports. For example, if you select Q5, the switch services traffic on Q5, Q6 and Q7 using Strictly Priority.

Select None to always use Weighted Fair Scheduling for the 10/100 Mbps

Ethernet ports.

Port This label shows the port you are configuring.

Weight Q0~Q7 When you select Weighted Fair Scheduling, enter the queue weight here.

Bandwidth is divided across the different traffic queues according to their weights.

Queues with larger weights get more guaranteed bandwidth than queues with smaller weights.

Apply

Cancel

Click Apply to save your changes back to the switch.

Click Cancel to begin configuring this screen afresh.

VES-1616F-3x Series User’s Guide

125

Chapter 17 Queuing Method

126

VES-1616F-3x Series User’s Guide