Free Network Performance Test tool - Iperf

According to wikipedia Iperf "is a commonly used network testing tool that can create TCP and UDP data streams and measure the throughput of a network that is carrying them. Iperf is a modern tool for network performance measurement written in C++."

This tool has to configure server side and client side to complete a test. It can test from client side to server side , also can test from both direction.

1. Download iperf 3 

The main download site is from https://iperf.fr/iperf-download.php.

2. Start it as server

Running command 'iperf -s' from command line as iperf server (ip address 100.99.136.66).

C:\Tools>iperf -s

------------------------------------------------------------

Server listening on TCP port 5001

TCP window size: 8.00 KByte (default)

------------------------------------------------------------

[188] local 100.99.136.66 port 5001 connected with 100.94.200.14 port 48410

[ ID] Interval       Transfer     Bandwidth

[188]  0.0-10.0 sec   121 MBytes   101 Mbits/sec

3. Run iperf as test client

User 'ipef -c' command to run from client test machine (ip adss 100.94.200.14)  to evaluate the network throughput based on TCP connection.

C:\tools>iperf -c 100.99.136.66

------------------------------------------------------------

Client connecting to 100.99.136.66, TCP port 5001

TCP window size: 8.00 KByte (default)

------------------------------------------------------------

[1912] local 100.94.200.14 port 48410 connected with 100.99.136.66 port 5001

[ ID] Interval       Transfer     Bandwidth

[1912]  0.0-10.0 sec   121 MBytes   101 Mbits/sec

4. Send 100MBytes data for testing

iperf -c 100.99.136.66 -n 100m

5. Bi-direction test

Simultaneous bi-directional bandwidth measurement: (-d argument)

To measure the bi-directional bandwidths simultaneousely, use the -d argument. If you want to test the bandwidths sequentially, use the -r argument (see previous test).

By default (ie: without the -r or -d arguments), only the bandwidth from the client to the server is measured.

C:\tools> iperf -c 100.99.136.66  -d

------------------------------------------------------------

Server listening on TCP port 5001

TCP window size: 85.3 KByte (default)

------------------------------------------------------------

------------------------------------------------------------

Client connecting to 10.1.1.1, TCP port 5001

TCP window size: 16.0 KByte (default)

------------------------------------------------------------

[ 5] local 10.6.2.5 port 60270 connected with 10.1.1.1 port 5001

[ 4] local 10.6.2.5 port 5001 connected with 10.1.1.1 port 2643

[ 4] 0.0-10.0 sec 76.3 MBytes 63.9 Mbits/sec

[ 5] 0.0-10.1 sec 1.55 MBytes 1.29 Mbits/sec

6. Parallel TCP connections

Parallel connections can be useful if you need to saturate the bandwidth of a link.  The bandwidth of a single TCP session can be greatly affected by the size of the receive window and the latency of the link.

iperf -s -i 1 (-i 1 means update terminal every second)

iperf -c 192.168.1.1 -t 30 -P 10

Add caption

7.  Other Parameters

iperf -c 12.12.12.12 -p 2233 -i 1 -t 60 -f M

Notes：

c：start iperf as client, followed ip address is remote server ip.
p：set specific server port, which should be same as server side's settings.
i：reporting intervals
t：length of test
f：change number output format

Other parameters can be found from https://iperf.fr/iperf-doc.php.