Quality Of Service - Cisco Catalyst 4500 series Administration Manual

Chapter 1 Product Overview

Quality of Service

QoS functionality on Catalyst 4900M, Catalyst 4948E, Catalyst 4948E-F, Supervisor Engine 6-E and
Note
Supervisor Engine 6L-E are equivalent.
The quality of service (QoS) feature prevents congestion by selecting network traffic and prioritizing it
according to its relative importance. Implementing QoS in your network makes network performance
more predictable and bandwidth use more effective.
The Catalyst 4500 series switch supports the following QoS features:
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Catalyst 4500 series switch supports trusted boundary, which uses the Cisco Discovery Protocol (CDP)
to detect the presence of a Cisco IP phone (such as the Cisco IP Phone 7910, 7935, 7940, and 7960) on
a switch port. If the telephone is not detected, the trusted boundary feature disables the trusted setting
on the switch port and prevents misuse of a high-priority queue.
The Catalyst 4500 series switch also supports QoS Automation (Auto QoS), which simplifies the
deployment of existing QoS features through automatic configuration.
Cisco Modular QoS Command-Line-Interface
Cisco Modular QoS CLI (MQC) is the framework that implements Cisco IOS software QoS. MQC
allows the user to define a traffic class, create a traffic policy (containing the QoS feature to be applied
to the traffic class), and attach the traffic policy to an interface. MQC is a cross-Cisco baseline that
provides a consistent syntax and behavior of QoS features across multiple product families. Cisco IOS
Software Release 12.2(40)SG complies to MQC for configuration of QoS features on the Supervisor
Engine 6-E. MQC enables rapid deployment of new features and technology innovations and facilitates
the management of network performance with respect to bandwidth, delay, jitter, and packet loss,
enhancing the performance of mission-critical business applications. The rich and advanced QoS
features are enabled using Cisco MQC.
Two-Rate Three-Color Policing
The Two-Rate Three-Color Policing feature (also termed Hierarchical QoS) limits the input or output
transmission rate of a class of traffic based on user-defined criteria and marks or colors packets by setting
the applicable differentiated services code point (DSCP) values. This feature is often configured on the
interfaces at the edge of a network to limit the rate of traffic entering or leaving the network. Using this
feature, traffic that conforms to user-defined criteria can be sent through the interfaces, while traffic that
exceeds or violates these criteria is sent out with a decreased priority setting or even dropped.
For information on QoS and Auto QoS, see
OL-30933-01
Classification and marking
Ingress and egress policing, including per-port per-VLAN policing
Sharing and shaping
Chapter 42, "Configuring Quality of Service."
Software Configuration Guide—Release IOS XE 3.6.0E and IOS 15.2(2)E
Layer 2 Software Features
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