2  QoS Configuration Approaches 
This chapter covers the following topics: 
z  QoS Configuration Approach Overview 
z  Configuring a QoS Policy 
QoS Configuration Approach Overview 
Two approaches are available for you to configure QoS: policy-based and non policy-based.   
Some QoS features can be configured in either approach while some can be configured only in one 
approach.  
Non Policy-Based Configuration 
In the non policy-based approach, you configure QoS service parameters without using a QoS policy. 
For example, to rate limit an interface, you can use the line rate feature to directly configure a rate limit 
on the interface rather than using a QoS policy.   
Policy-Based Configuration 
In the policy-based approach, QoS service parameters are configured through configuring QoS 
policies. A QoS policy defines what QoS actions to take on what class of traffic for purposes such as 
traffic shaping or traffic policing.   
Before configuring a QoS policy, be familiar with these concepts: class, traffic behavior, and policy.   
Class 
Classes are used to identify traffic.   
A class is identified by a class name and contains some match criteria for traffic identification. The 
relationship between the criteria is AND or OR.   
z  AND: A packet is considered as belonging to a class only when the packet matches all the criteria 
in the class.   
z  OR: A packet is considered as belonging to a class if it matches any of the criteria in the class.   
Traffic behavior 
A traffic behavior defines a set of QoS actions to take on packets, such as priority marking and traffic 
redirecting.   
Policy 
A policy associates a class with a traffic behavior to define what actions to take on which class of 
traffic. 
You can configure multiple class-behavior associations in a policy.