Cisco 10000 Series Configuration Manual page 407

Quality of service configuration guide

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Defining QoS for Multiple Policy Levels

In releases prior to Cisco IOS Release 12.0(22)S, you can specify QoS behavior at only one level. For

example, to shape two outbound queues of an interface, you must configure each queue separately,

defining only class-specific actions. You can define a minimum bandwidth for two traffic classes, but

you cannot define a combined maximum bandwidth for the two classes. As a result, you cannot configure

fair queues on virtual circuits where the total throughput of the fair queues must be within the virtual

circuit's committed rate.

To implement fair queues on virtual circuits and virtual LANs (VLANs), the Cisco 10000 series router

supports QoS with hierarchical queuing. Within the hierarchical QoS framework, you can enable the

router to prioritize and manage packets at three policy levels (physical, logical, and class levels), thereby

providing a high degree of granularity in traffic management. Congestion control mechanisms such as

weighted random early detection (WRED) and tail drop regulate network traffic and control congestion.

This chapter describes the various types of hierarchical policies and includes the following topics:

Hierarchical Policies, page 13-2

Components Common to All Types of Hierarchical Policies, page 13-3

Types of Hierarchical Policies, page 13-6

Hierarchical Policies and Oversubscription, page 13-11

Applying Child Policies Under Priority Classes, page 13-12

Interfaces Supporting Hierarchical Policies, page 13-12

Guidelines for Configuring QoS for Multiple Queues, page 13-13

Configuring QoS for Multiple Queues, page 13-13

Configuration Examples, page 13-22

Verifying the Configuration of Hierarchical Policies, page 13-27

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