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The Graph tab will be discussed in Chapter 8
.
7.4.3 Other Options
Apart from SNMP, there are a number of remote administration options including several third-party commercial tools. If remote access is the only consideration, vnc is an excellent choice. In particular,
the viewer requires no installation. It is under 200KB so it can be run from a floppy disk. It provides a very nice way to access an X Window session on a Unix system from a PC even if you dont want to
use it for management. Installation of the server binary is very straightforward. However, vnc will not provide multiuser access to Windows and can be sluggish over low-bandwidth connections such as
dial-up lines. Under these circumstances, you might consider Microsoft Terminal Server, Microsoft Corporations thin client architecture, which supports remote access. See
Chapter 11 for more
information on vnc. For other administrative tasks, there are a number of utilities that are sold as part of Microsofts
Resource Kits. While not free, these are generally modestly priced, and many of the tools can be downloaded from the Web at no cost. Some tools, while not specifically designed for remote
troubleshooting, can be used for that purpose if you are willing to allow appropriate file sharing. These include the System Policy Editor, Registry Editor, System Monitor, and Net Watcher, among
others. These are all briefly described by the Windows help system and more thoroughly in Microsoft published documentation.
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Chapter 8. Performance Measurement Tools
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 isnt 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.
Dont 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 neednt
worry about theoretical problems. And if users are screaming at your door, then it doesnt matter what the numbers prove.
8.1 What, When, and Where
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 pieces interact with one another. Even though the focus of this chapter is restricted to network performance, you shouldnt ignore the other pieces of
the puzzle. Problems may arise from the interaction of these pieces, or a problem with one of the pieces may look like a problem with another piece. A misconfigured or poorly designed application
can significantly increase the amount of traffic on a network. For example, Version 1.1 of the HTTP protocol provides for persistent connections that can significantly reduce traffic. Not using this
particular feature is unlikely to be a make or break issue. My point is, if you look only at the traffic on a network without considering software configurations, you may seem to have a hardware capacity
problem when a simple change in software might lessen the problem and, at a minimum, buy you a little more time.
This chapter will focus on tools used to collect information on network performance. The first step in analyzing performance is measuring traffic. In addition to problem identification and resolution, this
should be done as part of capacity planning and capacity management tuning. Several books listed in Appendix B
provide general discussions of application and host performance analysis. Of the issues related to measuring network traffic, the most important ones are what to measure, how
often, and where. Although there are no simple answers to any of these questions, what to measure is probably the hardest of the three. It is extremely easy to end up with so much data that you dont have
time to analyze it. Or you may collect data that doesnt match your needs or that is in an unusable format. If you keep at it, eventually you will learn from experience what is most useful. Take the time
to think about how you will use the data before you begin. Be as goal directed as possible. Just realize that, even with the most careful planning, when faced with a new, unusual problem, youll probably
think of something you wish you had been measuring.
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