Configuring The Ingress Priority Queue - Cisco WS-C3560-48PS-S Software Configuration Manual

Configuring Standard QoS

Configuring the Ingress Priority Queue

You should use the priority queue only for traffic that needs to be expedited (for example, voice traffic,
which needs minimum delay and jitter).
The priority queue is guaranteed part of the bandwidth to reduce the delay and jitter under heavy network
traffic on an oversubscribed ring (when there is more traffic than the backplane can carry, and the queues
are full and dropping frames).
SRR services the priority queue for its configured weight as specified by the bandwidth keyword in the
mls qos srr-queue input priority-queue queue-id bandwidth weight global configuration command.
Then, SRR shares the remaining bandwidth with both ingress queues and services them as specified by
the weights configured with the mls qos srr-queue input bandwidth weight1 weight2 global
configuration command.
Beginning in privileged EXEC mode, follow these steps to configure the priority queue. This procedure
is optional.
Command
Step 1 configure terminal
Step 2
mls qos srr-queue input
priority-queue queue-id bandwidth
weight
Step 3 end
Step 4
show mls qos interface queueing
or
show mls qos input-queue
Step 5 copy running-config startup-config
To return to the default setting, use the no mls qos srr-queue input priority-queue queue-id global
configuration command. To disable priority queueing, set the bandwidth weight to 0, for example, mls
qos srr-queue input priority-queue queue-id bandwidth 0.
This example shows how to assign the ingress bandwidths to the queues. Queue 1 is the priority queue
with 10 percent of the bandwidth allocated to it. The bandwidth ratios allocated to queues 1 and 2 is
4/(4+4). SRR services queue 1 (the priority queue) first for its configured 10 percent bandwidth. Then
SRR equally shares the remaining 90 percent of the bandwidth between queues 1 and 2 by allocating 45
percent to each queue:
Switch(config)# mls qos srr-queue input priority-queue 1 bandwidth 10
Switch(config)# mls qos srr-queue input bandwidth 4 4
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Purpose
Enter global configuration mode.
Assign a queue as the priority queue and guarantee bandwidth on the
internal ring if the ring is congested.
By default, the priority queue is queue 2, and 10 percent of the bandwidth
is allocated to it.
For queue-id, the range is 1 to 2.
•
• For bandwidth weight, assign the bandwidth percentage of the
internal ring. The range is 0 to 40. The amount of bandwidth that can
be guaranteed is restricted because a large value affects the entire ring
and can degrade performance.
Return to privileged EXEC mode.
Verify your entries.
(Optional) Save your entries in the configuration file.
Chapter 28 Configuring QoS
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