Testing your Network Performance

I have used iperf and jperf for years and have found it to be very valuable tool for testing my network performance.

You will need 2 devices (client/server) and it is very telling of your network. Test it both using WiFi and hardwired. Feel free to share your results and ask questions.

Purpose: Quickly verify whether a network can reliably support FlexRadio real-time traffic (audio, panadapters, waterfalls, and control).

These four tests identify the vast majority of FlexRadio network-related issues.

Before You Start

• Use iPerf3 (recommended)
• https://iperf.fr/iperf-download.php
• Start with wired Ethernet if possible
• Disable VPNs, QoS, traffic shaping, and heavy background traffic

Start the server on one system. Make note of the ip address, as you need it.

iperf3 -s

Test 1 – TCP Baseline (Forward)

Purpose: Basic stability and retransmissions

Command (Client):

You'll need the ip address from the server (above).

iperf3 -c <server_ip> -t 30

Good Results:

• Stable throughput
• Very low or zero retransmissions

Test 2 – TCP Reverse Direction

Purpose: Validate return path (critical for remote operation)

Command (Client):

iperf3 -c <server_ip> -R -t 30

Good Results:

• Similar performance to forward test
• No large increase in retransmissions

Test 3 – UDP Real-Time Simulation

Purpose: Simulate FlexRadio audio and spectrum traffic

Command (Client):

iperf3 -c <server_ip> -u -b 5M -t 30

Good Results:

• Packet loss: 0% (acceptable < 0.5%)
• Jitter: < 20 ms (preferably < 10 ms)
• Stable bitrate

This is the most important test for RX audio popping or dropouts.

Test 4 – UDP Margin / Stress Test

Purpose: Determine available headroom

Command (Client):

iperf3 -c <server_ip> -u -b 10M -t 30

Good Results:

• Slight jitter increase is acceptable
• Packet loss should remain very low

If this fails but the 5M test passes, the network is marginal.

What the Results Tell You

• Good TCP, bad UDP → Jitter or packet loss issue
• Wired OK, Wi-Fi bad → Wireless interference or congestion
• Reverse direction worse → Upload path or ISP buffering
• High retransmissions → Router, cabling, or NIC issue