118 Chapter 4: QoS Support on the Catalyst 5000 Family of Switches
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
• 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
• 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.
This page intentionally left blank This page intentionally left blank