Cisco Systems 3750E manual Queue Type Function, 36-16

Chapter 36 Configuring QoS

Understanding QoS

Figure 36-10 Queueing and Scheduling Flowchart for Ingress Ports on Catalyst 3560-E Switches

Start
Read QoS label
(DSCP or CoS value).
Determine ingress queue
number, buffer allocation,
and WTD thresholds.
Are thresholds	Yes
being exceeded?
No

Queue the packet. Service

the queue according to

the SRR weights.

Drop packet.

Send packet to the internal ring.

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Note SRR services the priority queue for its configured share before servicing the other queue.

The switch supports two configurable ingress queues, which are serviced by SRR in shared mode only. Table 36-1describes the queues.

Table 36-1	Ingress Queue Types
Queue Type1	Function
Normal	User traffic that is considered to be normal priority. You can configure three different
	thresholds to differentiate among the flows. You can use the mls qos srr-queue input
	threshold, the mls qos srr-queue input dscp-map, and the mls qos srr-queue input
	cos-mapglobal configuration commands.
Expedite	High-priority user traffic such as differentiated services (DF) expedited forwarding or
	voice traffic. You can configure the bandwidth required for this traffic as a percentage
	of the total traffic or total stack traffic on Catalyst 3750-E switches by using the mls
	qos srr-queue input priority-queueglobal configuration command. The expedite queue
	has guaranteed bandwidth.

1. The switch uses two nonconfigurable queues for traffic that is essential for proper network and stack operation.

You assign each packet that flows through the switch to a queue and to a threshold. Specifically, you map DSCP or CoS values to an ingress queue and map DSCP or CoS values to a threshold ID. You use the mls qos srr-queue input dscp-map queue queue-id{dscp1...dscp8 threshold threshold-id

	Catalyst 3750-E and 3560-E Switch Software Configuration Guide
36-16	OL-9775-02