Configuration Guidelines - Cisco Catalyst 2975 Software Configuration Manual

Configuring Standard QoS
These sections contain this configuration information:
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Configuration Guidelines

Follow these guidelines when the expedite queue is enabled or the egress queues are serviced based on
their SRR weights:
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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
allocation for a queue-set by using the mls qos queue-set output qset-id threshold queue-id
drop-threshold1 drop-threshold2 reserved-threshold maximum-threshold global configuration commands.
Each threshold value is a percentage of the queues allocated buffers, which you specify by using the mls
qos queue-set output qset-id buffers allocation1 ... allocation4 global configuration command. The
queues use WTD to support distinct drop percentages for different traffic classes.
The egress queue default settings are suitable for most situations. You should change them only when
Note
you have a thorough understanding of the egress queues and if these settings do not meet your QoS
solution.
Catalyst 2975 Switch Software Configuration Guide
33-68
Configuration Guidelines, page 33-68
Allocating Buffer Space to and Setting WTD Thresholds for an Egress Queue-Set, page 33-68
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Mapping DSCP or CoS Values to an Egress Queue and to a Threshold ID, page 33-70
Configuring SRR Shaped Weights on Egress Queues, page 33-72
Configuring SRR Shared Weights on Egress Queues, page 33-73
Configuring the Egress Expedite Queue, page 33-74
Limiting the Bandwidth on an Egress Interface, page 33-74
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.
Chapter 33
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Configuring QoS
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