Cisco Catalyst QoS: Quality of Service in Campus Networks

118 Chapter 4: QoS Support on the Catalyst 5000 Family of Switches

Summary

The Catalyst 5000 Family of switches supports QoS with only specific Supervisors and line

modules. These switches support QoS features limited to classification of untagged frames,

marking based on ACEs, and output scheduling. These features classify frames solely on

CoS values. For most applications, DSCP classification is desirable. As a result, network

designs should not introduce the Catalyst 5000 Family of switches into a QoS end-to-end

architecture; instead, utilize the Catalyst 5000 Family of switches only in existing deploy-

ments. In summary, the QoS feature support on the Catalyst 5000 Family of switches is as

follows:

• QoS support requires one of the following Supervisors: Supervisor III with NFFC II,

Supervisor IIG, or Supervisor IIIG.

• QoS support requires traffic ingress and egress using the following line modules or

uplink modules: WS-X5234-RJ45, WS-X5236-FX-MT, WS-X5239-RJ21, WS-

U5537-FETX, or WS-U5538-FEFX-MMF.

• No support for input scheduling exists.

• Classification based on CoS only; no support for classification based on IP precedence

or DSCP.

• Marking of CoS and ToS supported with limitations with regard to MLS.

• CoS value determines ToS value for ACE-based marking.

• Congestion avoidance achieved via WRED using a 1q4t mechanism.

• Global mapping of CoS values to thresholds is configurable.

• Thresholds are configurable on a global basis.

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