Cisco Systems 3750E manual Allocating Buffer Space Between the Ingress Queues, 36-71

Chapter 36 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.

	Command	Purpose
Step 1
	configure terminal	Enter global configuration mode.
Step 2
	mls qos srr-queue input buffers	Allocate the buffers between the ingress queues
	percentage1 percentage2	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.
Step 3
	end	Return to privileged EXEC mode.
Step 4
	show mls qos interface buffer	Verify your entries.
	or
	show mls qos input-queue
Step 5
	copy running-config startup-config	(Optional) Save your entries in the configuration file.

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.

	Catalyst 3750-E and 3560-E Switch Software Configuration Guide
OL-9775-02		36-71