Microbenchmark and tune network performance with iPerf3 and Linux traffic control
Introduction
Set up Arm-based Linux systems for network performance testing with iPerf3
Microbenchmark the network connection
Simulate different network conditions
Tune kernel parameters
Next Steps

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You can further optimize network performance by adjusting Linux kernel parameters and testing across different environments, including local-to-cloud scenarios.

Connect from a local machine

You can look at ways to mitigate performance degradation due to events such as packet loss.

In this example, you will connect to the server node a local machine to demonstrate a longer response time. Check the iPerf3 installation guide to install iPerf3 on other operating systems.

Before starting the test:

  • Update your cloud server’s security group to allow incoming TCP connections from your local machine’s public IP.
  • Use the public IP address of the cloud instance when connecting.

Running iPerf3 on the local machine and connecting to the cloud server shows a longer round trip time, in this example more than 40ms.

Run this command on your local computer:

    

        
        
iperf3 -c <server-public-IP> -v

Compared to over 2 Gbit/sec within AWS, this test shows a reduced bitrate (~157 Mbit/sec) due to longer round-trip times (for example, >40ms).

    

        
        Starting Test: protocol: TCP, 1 streams, 131072 byte blocks, omitting 0 seconds, 10 second test, tos 0
...
Test Complete. Summary Results:
[ ID] Interval           Transfer     Bitrate
[  8]   0.00-10.01  sec   187 MBytes   157 Mbits/sec                  sender
[  8]   0.00-10.03  sec   187 MBytes   156 Mbits/sec                  receiver

Modify kernel parameters on the server

On the server, you can configure Linux kernel runtime parameters with the sysctl command.

There are a plethora of values to tune that relate to performance and security. The following command can be used to list all available options. The Linux kernel documentation provides a more detailed description of each parameter.

    

        
        
sysctl -a | grep tcp
Note

Depending on your operating system, some parameters might not be available. For example, on AWS Ubuntu 22.04 LTS, only the cubic and reno congestion control algorithms are supported:

    

        
        
net.ipv4.tcp_available_congestion_control = reno cubic

Increase TCP buffer sizes

You can increase the kernel’s read and write buffer sizes on the server improve throughput on high-latency connections. This consumes more system memory but allows more in-flight data.

To try it, run the following commands on the server:

    

        
        
sudo sysctl net.core.rmem_max=134217728 # default = 212992
sudo sysctl net.core.wmem_max=134217728 # default = 212992

Then, restart the iPerf3 server:

    

        
        
iperf3 -s

Now rerun iPerf3 again on your local machine:

    

        
        
iperf3 -c <server-public-IP> -v

Without changing anything on the client, the throughput improved by over 60%.

    

        
        Test Complete. Summary Results:
[ ID] Interval           Transfer     Bitrate
[  8]   0.00-10.00  sec   308 MBytes   258 Mbits/sec                  sender
[  8]   0.00-10.03  sec   307 MBytes   257 Mbits/sec                  receiver

You’ve now completed a guided introduction to:

  • Network performance microbenchmarking
  • Simulating real-world network conditions
  • Tuning kernel parameters for high-latency links

You can now explore this area further by testing other parameters, tuning for specific congestion control algorithms, or integrating these benchmarks into CI pipelines for continuous performance evaluation.

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