33-15
Catalyst 3750 Switch Software Configuration Guide
OL-8550-02
Chapter 33 Configuring QoS
Understanding QoS
Queueing and Scheduling on Ingress Queues
Figure 33-8 shows the queueing and scheduling flowchart for ingress ports.
Figure 33-8 Queueing and Scheduling Flowchart for Ingress Ports
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 33-1 describes the queues.
86693
Read QoS label
(DSCP or CoS value).
Determine ingress queue
number, buffer allocation,
and WTD thresholds.
Are thresholds
being exceeded?
Queue the packet. Service
the queue according to
the SRR weights.
Send packet to
the stack ring.
Drop packet.
Start
Ye s
No
Table 33-1 Ingress Queue Types
Queue Type
1
1. The switch uses two nonconfigurable queues for traffic that is essential for proper network and stack operation.
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-map global 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 stack traffic by using the mls qos srr-queue input priority-queue global
configuration command. The expedite queue has guaranteed bandwidth.
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