Configuring Egress Queue-Set Characteristics; Allocating Buffer Space To And Setting Wtd Thresholds For An Egress Queue-Set; Mapping Dscp Or Cos Values To An Egress Queue-Set And To A Threshold Id - Cisco Catalyst 3750 Software Configuration Manual

Chapter 26 Configuring QoS

Configuring Egress Queue-Set Characteristics

Depending on the complexity of your network and your QoS solution, you might need to perform all of
the tasks in the next sections. You will need to make decisions about these characteristics:
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These sections describe how to configure egress queue-set characteristics:
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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 memory
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 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-id buffers allocation1 ... allocation4 global configuration command.
The queues use WTD to support distinct drop percentages for different traffic classes.
The egress queue-set default settings are suitable for most situations. You should change them only when
Note
you have a thorough understanding of the queues and only if these settings do not meet your QoS
solution.
Beginning in privileged EXEC mode, follow these steps to configure the memory allocation and drop
thresholds for a queue-set. This procedure is optional.
78-15870-01
Which packets are mapped by DSCP or CoS value to each queue and threshold ID?
What drop percentage thresholds apply to the queue-set (four egress queues per port), and how much
reserved and maximum memory is needed for the traffic type?
How much of the fixed buffer space is allocated to the queue-set?
Does the bandwidth of the port need to be rate limited?
How often should the egress queue-set be serviced and which technique (shaped, shared, or both)
should be used?
Allocating Buffer Space to and Setting WTD Thresholds for an Egress Queue-Set, page 26-69
(optional)
Mapping DSCP or CoS Values to an Egress Queue-Set and to a Threshold ID, page 26-71
Configuring SRR Shaped Weights on an Egress Queue-Set, page 26-72
Configuring SRR Shared Weights on an Egress Queue-Set, page 26-73
Limiting the Egress Bandwidth on a Queue-Set, page 26-74 (optional)
Catalyst 3750 Metro Switch Software Configuration Guide
Configuring Standard QoS
(optional)
(optional)
(optional)
26-69