Chapter 36 Configuring QoS

Configuring Standard QoS

These sections contain this configuration information:

Configuration Guidelines, page 36-74

Allocating Buffer Space to and Setting WTD Thresholds for an Egress Queue-Set, page 36-74(optional)

Mapping DSCP or CoS Values to an Egress Queue and to a Threshold ID, page 36-76(optional)

Configuring SRR Shaped Weights on Egress Queues, page 36-78(optional)

Configuring SRR Shared Weights on Egress Queues, page 36-79(optional)

Configuring the Egress Expedite Queue, page 36-79(optional)

Limiting the Bandwidth on an Egress Interface, page 36-80(optional)

Configuration Guidelines

Follow these guidelines when the expedite queue is enabled or the egress queues are serviced based on their SRR weights:

If the egress expedite queue is enabled, it overrides the SRR shaped and shared weights for queue 1.

If the egress expedite queue is disabled and the SRR shaped and shared weights are configured, the shaped mode overrides the shared mode for queue 1, and SRR services this queue in shaped mode.

If the egress expedite queue is disabled and the SRR shaped weights are not configured, SRR services this queue in shared mode.

Allocating Buffer Space to and Setting WTD Thresholds for an Egress Queue-Set

You can guarantee the availability of buffers, set WTD thresholds, and configure the maximum memory allocation for a queue-set by using the mls qos queue-set output qset-idthreshold queue-iddrop-threshold1drop-threshold2reserved-thresholdmaximum-thresholdglobal configuration command.

Each threshold value is a percentage of the queue’s allocated memory, which you specify by using the mls qos queue-set output qset-idbuffers allocation1 ... allocation4 global configuration command. The queues use WTD to support distinct drop percentages for different traffic classes.

Note The egress queue default settings are suitable for most situations. You should change them only when you have a thorough understanding of the egress queues and if these settings do not meet your QoS solution.

 

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Cisco Systems 3750E manual Configuration Guidelines, 36-74