October 2011

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I am often asked to measure the bandwidth of a network path. Many users test this using a simple HTTP download or with speedtest.net. Unfortunately, any test using TCP will produce inaccurate results, due to the limitations of a session-oriented protocol. TCP window size, latency, and the bandwidth of the return channel (for ACK messages) all affect the results. The most reliable way to measure true bandwidth is with UDP. That’s where my friends iperf and bwm-ng come in handy.

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