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Advanced Network Testing: Measuring Throughput with iPerf3

While MTR measures latency and packet loss, iPerf3 is the industry-standard tool for measuring raw bandwidth throughput (speed).

Unlike a standard file download test (which can be limited by disk speed), iPerf3 tests pure network capacity between two points via TCP or UDP.

How it works:
iPerf3 works in a Client-Server model. 
1. You run iPerf3 in Server Mode on your VPS.
2. You run iPerf3 in Client Mode on your local computer (or another server).
3. They blast traffic at each other to measure the maximum speed.

Step 1: Installation

You need to install iPerf3 on both the source and the destination machine.

Linux (VPS)

# Ubuntu / Debian
sudo apt update && sudo apt install iperf3 -y

# AlmaLinux / CentOS / Rocky
sudo dnf install iperf3 -y

Windows (Local Computer)

Download the latest iperf3 binaries from the official website. Extract the zip file and open PowerShell in that folder.

Step 2: Prepare the Server (VPS)

On your Tilaa VPS, start iPerf3 in server mode. This tells it to listen for incoming tests.

Firewall Requirement:
By default, iPerf3 listens on port 5201. You must allow this port in your firewall, otherwise the connection will fail.

UFW: sudo ufw allow 5201/tcp
FirewallD: sudo firewall-cmd --permanent --add-port=5201/tcp && sudo firewall-cmd --reload

Start the listener:

iperf3 -s

The terminal will show: Server listening on 5201. Leave this window open.

Step 3: Run the Test (Local Computer)

Now, from your local computer (or the other server), connect to your VPS IP.

Test A: Upload Speed (You - VPS)

This measures how fast you can send data TO the server.

# Syntax: iperf3 -c 
iperf3 -c 84.22.x.x

Test B: Download Speed (VPS - You)

This is usually the most important test. Add the -R (Reverse) flag to make the VPS send data to you.

iperf3 -c 84.22.x.x -R

Step 4: Advanced Testing (Parallel Streams)

A single TCP connection is sometimes limited by latency or CPU protocols (TCP Window Scaling). To test the true capacity of the line, force multiple parallel connections using the -P flag.

Test with 4 parallel streams:

iperf3 -c 84.22.x.x -P 4 -R

If the sum of the streams is significantly higher than the single stream test, your connection is healthy, but latency might be limiting single-thread performance.

Step 5: Providing Results to Support

If you are diagnosing a speed issue with our support team, please include:

  1. The full output of the iPerf3 test (copy-paste the text).
  2. An MTR report run at the same time (to check for packet loss during load).
  3. Your local public IP address.