20

Queuing Method

This chapter introduces SPQ and WFQ.

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

Table 49 Physical Queue Priority

QUEUE

PRIORITY

Q7

8

(highest)

 

 

 

Q6

7

 

 

 

 

Q5

6

 

 

 

 

Q4

5

 

 

 

 

Q3

4

 

 

 

 

Q2

3

 

 

 

 

Q1

2

 

 

 

 

Q0

1

(lowest)

 

 

 

20.1.1 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, 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. SPQ does not automatically adapt to changing network requirements.

 

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