Chapter 18 Queuing Method; Queuing Method Overview; Strict Priority Queuing (Spq); Weighted Round Robin Scheduling (Wrr) - ZyXEL Communications Dimension ES-2108 User Manual

This chapter introduces the queuing methods supported.

18.1 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.

Table 39 Physical Queue Priority

QUEUE
Q3
Q2
Q1
Q0

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 Round Robin Scheduling (WRR)

Round Robin Scheduling services queues on a rotating basis and is activated only when a port
has more traffic than it can handle. A queue is a given an amount of bandwidth irrespective of
the incoming traffic on that port. This queue then moves to the back of the list. The next queue
is given an equal amount of bandwidth, and then moves to the end of the list; and so on,
depending on the number of queues being used. This works in a looping fashion until a queue
is empty.

Chapter 18 Queuing Method

PRIORITY
4 (highest)
3
2
1 (lowest)
C
H A P T E R
Queuing Method
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