Introduction

In this chapter, we will discuss the basic concepts behind Quality of Service (QoS), the need for it, and we will introduce you to several of the types of QoS mechanisms available. Quality of Service itself is not something that you configure on a Cisco router, rather it is an overall term that refers to a wide variety of mechanisms used to influence traffic patterns on a network.

Congestion Management is a collection of QoS mechanisms that will deal with network congestion as it occurs and will perform various actions on the traffic that is congesting the network. There are several congestion management mechanisms and each behaves differently. This chapter will introduce you to the overall concept of congestion management and some of the congestion management mechanisms that are available on Cisco routers.

Congestion avoidance is another classification within the larger umbrella of QoS mechanisms that focuses on preventing congestion, rather than dealing with it as it happens. This does not mean that congestion avoidance is any better or worse than congestion management, it is simply different. This chapter will discuss the theory behind congestion avoidance and present some possible scenarios where it may be preferable to use congestion avoidance, rather than congestion management.

Policing and Traffic Shaping are other groups of mechanisms that may help with network congestion and provide QoS to your network traffic. This chapter will introduce concepts and theories surrounding policing and shaping and will discuss where these may be preferable to other QoS...