Testing Network Performance

Network performance problems can sometimes be inscrutable. Why do you get 3MB/s transfer rates from one site but only 3KB/s from another site? Why do some web pages appear almost instantaneously while others make you wait for seconds before displaying anything at all? Unfortunately, many of these problems are due to deficiencies on the Internet at large, and you may not be able to fix them. Other problems are more localized, though. In order to tell these problem types apart, you must conduct tests or at least know the symptoms of different types of problems.

The two most fundamental measures of network performance are throughput and latency. These are measures of the overall data transfer rate and the time for a signal to pass from one site to another and back again, respectively. Throughput is important when you're downloading large files, such as Linux CD-R images. Latency is important when you're using a highly interactive protocol, such as a remote login tool. In addition to these two speed measures, diagnosing problems with specific hardware, such as routers and DNS servers, deserves some attention. When these devices malfunction, you can get sporadic or constant network performance problems.

Note Network performance can vary overtime. On a business's LAN, performance is likely to be worst during the workday, as employees go about their daily routines. Regional Internet transfers are likely to be slowest in the evening, when the Internet is clogged with home users browsing the Web. You may want to perform several tests over time to help determine the cause of problems and plan for future local network expansions.

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