Measuring network throughput

Bit rates
Name	Symbol	Multiple
bit per second	bit/s	1	1
Decimal prefixes (SI)
kilobit per second	kbit/s	103	10001
megabit per second	Mbit/s	106	10002
gigabit per second	Gbit/s	109	10003
terabit per second	Tbit/s	1012	10004
Binary prefixes (IEC 80000-13)
kibibit per second	Kibit/s	210	10241
mebibit per second	Mibit/s	220	10242
gibibit per second	Gibit/s	230	10243
tebibit per second	Tibit/s	240	10244

Throughput of a network can be measured using various tools available on different platforms. This page explains the theory behind what these tools set out to measure and the issues regarding these measurements.

Reasons for measuring throughput in networks. People are often concerned about measuring the maximum data throughput in bits per second of a communications link or network access. A typical method of performing a measurement is to transfer a 'large' file from one system to another system and measure the time required to complete the transfer or copy of the file. The throughput is then calculated by dividing the file size by the time to get the throughput in megabits, kilobits, or bits per second.

Unfortunately, the results of such an exercise will often result in the goodput which is less than the maximum theoretical data throughput, leading to people believing that their communications link is not operating correctly. In fact, there are many overheads accounted for in throughput in addition to transmission overheads, including latency, TCP Receive Window size and system limitations, which means the calculated goodput does not reflect the maximum achievable throughput.

The Maximum bandwidth can be calculated as follows:

${\displaystyle \mathrm {Throughput} \leq {\frac {\mathrm {RWIN} }{\mathrm {RTT} }}\,\!}$

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