Chapter 7. Understanding and Using Basic Network Statistics

Before beginning this chapter, please make sure that you understand the material in Chapter 2, "Policy-Based Network Management." The operational objectives for network management from Chapter 2, in conjunction with the material presented here, will assist you in defining measurable policies and agreements.

Why does a network manager need to have basic statistical knowledge? And what probability and statistical knowledge is needed to understand networking data? This chapter addresses these questions. In particular, it will focus on presenting the level of statistical knowledge that we feel is needed to understand network management and performance, especially with regard to service level objectives/agreements. The only mathematics needed to understand this chapter is algebra.

This chapter discusses the following:

• Reasons for understanding some very basic statistics for network management and analysis

• Some basic statistics needed for network management and performance analysis

• Using these statistics to analyze or understand performance data

We will first concentrate on some basic statistics that should help you understand the data being collected. Second, we will go over some preliminaries to assist you in choosing the variables needed to analyze the performance and capacity on your network.

NOTE

Most of the equations and figures in this chapter were created using a "mathematical scratchpad" called Mathcad from Mathsoft, Inc., 101 Main Street, Cambridge, MA 02142-1521. Mathcad has a scratchpad-like interface and the software uses real mathematical notation, which makes it easy to learn and deploy by network managers and analysts.