The switch also uses two nonconfigurable queues for traffic that are essential for proper network and stack
operation.
Note
The following table describes the two configurable ingress queues.
Table 60: Configurable Ingress Queue Types
FunctionQueue
Type
User traffic that is considered to be normal priority.
You can configure three different thresholds to differentiate among the flows.
Use the following global configuration commands:
•
mls qos srr-queue input threshold
•
mls qos srr-queue input dscp-map
•
mls qos srr-queue input cos-map
Normal
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 the switches by using the mls qos srr-queue input priority-queue global
configuration command.
The expedite queue has guaranteed bandwidth.
Expedite
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 dscp1...dscp8} or
the mls qos srr-queue input cos-map queue queue-id {cos1...cos8 | threshold threshold-id cos1...cos8}
global configuration command. You can display the DSCP input queue threshold map and the CoS input
queue threshold map by using the show mls qos maps privileged EXEC command.
WTD Thresholds
The queues use WTD to support distinct drop percentages for different traffic classes. Each queue has three
drop thresholds: two configurable (explicit) WTD thresholds and one nonconfigurable (implicit) threshold
preset to the queue-full state.
You assign the two explicit WTD threshold percentages for threshold ID 1 and ID 2 to the ingress queues by
using the mls qos srr-queue input threshold queue-id threshold-percentage1 threshold-percentage2 global
configuration command. Each threshold value is a percentage of the total number of allocated buffers for the
queue. The drop threshold for threshold ID 3 is preset to the queue-full state, and you cannot modify it.
Related Topics
Weighted Tail Drop, on page 554
Consolidated Platform Configuration Guide, Cisco IOS Release 15.2(4)E (Catalyst 2960-X Switches)
558
Information About QoS
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