Cisco Systems OL-8550-09 Allocating Buffer Space Between the Ingress Queues, Allocating Bandwidth Between the Ingress Queues

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Catalyst 3750 SwitchSoftware Configuration Guide
OL-8550-09
Chapter35 Configuring QoS
Configuring Standard QoS
This example shows how to map DSCP values 0 to 6 to ingress queue 1 and to threshold 1 with a drop
threshold of 50 percent. It maps DSCP values 20 to 26 to ingress queue 1 and to threshold 2 with a drop
threshold of 70 percent:
Switch(config)# mls qos srr-queue input dscp-map queue 1 threshold 1 0 1 2 3 4 5 6
Switch(config)# mls qos srr-queue input dscp-map queue 1 threshold 2 20 21 22 23 24 25 26
Switch(config)# mls qos srr-queue input threshold 1 50 70
In this example, the DSCP values (0 to 6) are assigned the WTD threshold of 50 percent and will be
dropped sooner than the DSCP values (20 to 26) assigned to the WTD threshold of 70 percent.
Allocating Buffer Space Between the Ingress Queues
You define the ratio (allocate the amount of space) with which to divide the ingress buffers between the
two queues. The buffer and the bandwidth allocation control how much data can be buffered before
packets are dropped.
Beginning in privileged EXEC mode, follow these steps to allocate the buffers between the ingress
queues. This procedure is optional.
To return to the default setting, use the no mls qos srr-queue input buffers global configuration
command.
This example shows how to allocate 60 percent of the buffer space to ingress queue 1 and 40 percent of
the buffer space to ingress queue 2:
Switch(config)# mls qos srr-queue input buffers 60 40
Allocating Bandwidth Between the Ingress Queues
You need to specify how much of the available bandwidth is allocated between the ingress queues. The
ratio of the weights is the ratio of the frequency in which the SRR scheduler sends packets from each
queue. The bandwidth and the buffer allocation control how much data can be buffered before packets
are dropped. On ingress queues, SRR operates only in shared mode.
Command Purpose
Step1 configure terminal Enter global configuration mode.
Step2 mls qos srr-queue input buffers
percentage1 percentage2
Allocate the buffers between the ingress queues
By default 90 percent of the buffers are allocated to queue 1, and 10
percent of the buffers are allocated to queue 2.
For percentage1 percentage2, the range is 0 to 100. Separate each value
with a space.
You should allocate the buffers so that the queues can handle any
incoming bursty traffic.
Step3 end Return to privileged EXEC mode.
Step4 show mls qos interface buffer
or
show mls qos input-queue
Verify your entries.
Step5 copy running-config startup-config (Optional) Save your entries in the configuration file.