Introduction

In this chapter, we introduce the default queuing mechanisms used on interfaces of various speeds and examine the reasons for using different queuing mechanisms on different types of interfaces. You should pay particular attention to the fact that the choice of different queuing methods as the default behavior for an interface is based on bandwidth.

This chapter also introduces some basic types of queuing, such as priority and custom queuing. We will investigate, in detail, the benefits and drawbacks of these methods, and thereby provide the basis for making a decision as to whether these queuing methods are appropriate for implementation on your network.

This chapter also introduces the theory of random discard congestion avoidance. We discuss where this might be used, where it may or may not be needed, and what the benefits and drawbacks of the random discard method of congestion avoidance are. This discussion will be continued in later chapters, as some of these technologies are the foundation of other, more advanced, methods.

Using FIFO Queuing

As network traffic reaches an ingress or egress point, such as a router interface, network devices, such as a router, must be able to adequately process this traffic as it is being received. FIFO (first in/first out) queuing is the most basic approach to ordering traffic for proper communication. Like a line at a carnival ride, a FIFO queue places all packets in a single line as they enter the interface.

Packets are processed by the router in the same...