Introduction
When troubleshooting connectivity issues to MasterDC, the technical team may ask you to test the network throughput between your device and MasterDC. We use the iPerf3 tool to measure throughput between two points in a network. This guide explains what iPerf3 is used for and how to install and use it.
What is iPerf3
iPerf3 is an open-source command-line tool used to measure the maximum bandwidth in IP networks. It simulates network traffic and measures its quality. It is suitable for:
- verifying actual transfer speeds (LAN, WAN, VPN, Wi-Fi);
- diagnosing slow communication;
- testing new infrastructure (servers, switches, firewalls);
- verifying network link quality before deploying applications;
- simulating network load.
The tool supports data transfer over TCP, SCTP and UDP and works in both IPv4 and IPv6 networks. For testing, you can set parameters such as test duration, reporting intervals, or buffer size. For more accurate measurements, you can run multiple parallel streams. iPerf3 primarily measures in client → server mode but also allows reverse testing for bidirectional throughput measurement.
After the test completes, the tool displays the achieved transfer speed (throughput), packet loss, jitter, and any retransmissions.
Test Modes: TCP/SCTP or UDP
iPerf3 allows measurements in two modes based on the transport protocol used: TCP (and SCTP) or UDP. The selected mode affects what is measured during the test and how the data transfer behaves.
TCP and SCTP Mode
This mode is suitable for measuring the maximum achievable transfer speed between two devices. TCP is a protocol that verifies data delivery and retransmits data if packet loss is detected. It provides a realistic overview of how the network performs under normal operation. This is the default and most commonly used mode. In this mode, iPerf3:
- measures bandwidth (throughput), i.e., how fast data can be transferred;
- displays information about packet size (MSS/MTU);
- allows adjustment of the TCP window size (via buffer settings);
- shows any data retransmissions.
UDP Mode
We recommend UDP mode for testing connection quality and for latency-sensitive applications such as VoIP or streaming. Because UDP does not verify delivery or retransmit lost packets, it allows you to determine at what load packet loss or quality degradation begins. In this mode, iPerf3:
- allows you to set a target transfer rate;
- measures packet loss;
- measures jitter (variation in packet delay);
- supports multicast testing (sending data from one device to multiple recipients).
Download and Installation of iPerf3
iPerf3 is available for most commonly used operating systems. You can download it from the official website.
Installation on Windows
- Download the iPerf3 ZIP file for Windows from the official website.
- Extract the ZIP file to any directory (e.g., C:\iperf3).
- Open Command Prompt (cmd) or PowerShell.
- Navigate to the iPerf3 folder using:
cd C:\iperf3 - Verify the installation with:
iperf3.exe --version. If version information is displayed, the installation was successful.
Istallation on Linux
On most Linux systems, iPerf3 is available directly from the distribution repositories.
Ubuntu and Debian
- Update the package list before installation:
sudo apt update - Install iPerf3:
sudo apt install iperf3 - After installation, run
iperf3 --version. If the terminal displays the iPerf3 version number, the installation was successful.
Fedora
- Update the package list before installation:
sudo dnf update - Install iPerf3:
sudo dnf install iperf3 - After installation, run
iperf3 --version. If the terminal displays the iPerf3 version number, the installation was successful.
CentOS and RHEL
- Update the package list before installation:
sudo yum update - Install iPerf3:
sudo yum install iperf3 - After installation, run
iperf3 --version. If the terminal displays the iPerf3 version number, the installation was successful.
Installation on macOS
If you have Homebrew (a package manager for macOS) installed, the easiest way to install iPerf3 is: brew install iperf3
Alternatively, you can download the macOS binaries from the official website. Then follow these steps:
- Extract the downloaded file to any directory (e.g., ~/iperf3).
- Open Terminal and navigate to the folder using:
cd ~/iperf3 - Run iPerf3 with:
./iperf3 --version. The terminal will display the version number, which means iPerf3 is ready to use.
Running a Test with iPerf3
On the server side, the test is initiated by MasterDC. It is typically used when troubleshooting connectivity issues. You will receive the server IP addresses in advance to perform the tests.
Running the Client and a Basic TCP Test (client → server)
On your device, connect to the MasterDC iPerf3 server and start the test with:
iperf3 -c <server_IP_addresses>For example: iperf3 -c 123.456.7.89. After the test finishes, the results (throughput, packet loss, etc.) will be displayed.
Reverse Test (server → client)
To measure bidirectional throughput, use the reverse mode command:
iperf3 -c <server_IP_addresses> -RAdvanced Test Parameters
You can add the following parameters to the command if you need specific information or more detailed results.
-t <seconds>– sets the test duration, e.g.,-t 30-i <seconds>– sets the interval for reporting intermediate results-P <numbers>– specifies the number of parallel streams for more accurate measurement-u– uses UDP instead of TCP-b <rate>– sets the target transfer rate for a UDP test-J– outputs results in JSON format for automated processing
Examples of advanced tests:
- TCP test for 30 seconds with 4 parallel streams:
iperf3 -c 123.456.7.89 -t 30 -P 4 - UDP test with a target rate of 100 Mbps:
iperf3 -c 123.456.7.89 -u -b 100M