# Defining Service Levels with Traffic Classes and Traffic-Class Groups

This chapter provides information for configuring traffic classes and traffic-class groups on the E Series router.

QoS topics are discussed in the following sections:

- Traffic Class and Traffic-Class Groups Overview
- Configuring Traffic Classes That Define Service Levels
- Configuring Traffic-Class Groups That Define Service Levels
- Monitoring Traffic Classes and Traffic-Class Groups for Defined Levels of Service