Everything on your network may be working, but using it can still be a frustrating experience. Often, a poorly performing system is worse than a broken system. As a user on a broken system, you know when to give up and find something else to do. And as an administrator, it is usually much easier to identify a component that isn’t working at all than one that is still working but performing poorly. In this chapter, we will look at tools and techniques used to evaluate network performance.
This chapter begins with a brief overview of the types of tools available. Then we look at ntop, an excellent tool for watching traffic on your local network. Next, I describe mrtg, rrd, and cricket—tools for collecting traffic data from remote devices over time. RMON, monitoring extensions to SNMP, is next. We conclude with tools for use on Microsoft Windows systems.
Don’t overlook the obvious! Although we will look at tools for measuring traffic, user dissatisfaction is probably the best single indicator of the health of your network. If users are satisfied, you needn’t worry about theoretical problems. And if users are screaming at your door, then it doesn’t matter what the numbers prove.
Network performance will depend on many things—on the applications you are using and how they are configured, on the hosts running these applications, on the networking devices, on the structure and design of the network as a whole, and on how these ...