Skip to content
Atomic Logo
  • Home Fibre

    View All Home Fibre Packages
    Fast reliable internet for Gaming, Streaming and Work-from-home 🚀

    Octotel Fibre

    Octotel Home Fibre
    Uncapped Octotel Home Fibre with speeds up to 1Gbps

    Frogfoot Fibre

    Frogfoot Home Fibre
    Uncapped Frogfoot Home Fibre with speeds up to 1Gbps

    Vumatel Logo

    Vumatel Home Fibre
    Uncapped Vumatel Home Fibre with speeds up to 1Gbps

    Openserve Fibre

    Openserve Home Fibre
    Uncapped Openserve Home Fibre with speeds up to 500Mbps

  • Business Fibre

    View All Business Fibre Packages
    Fast reliable internet with Priority Support and Fast Repair Times 🚀

    Octotel Fibre

    Octotel Business Fibre
    Uncapped Octotel Business Fibre with speeds up to 1Gbps

    Frogfoot Business Fibre
    Exceptional value for businesses in residential areas and select business complexes with speeds up to 1Gbps

    Vumatel Logo

    Vumatel Business Fibre
    Uncapped Vumatel Business Fibre with speeds up to 1Gbps on 12 & 24 month contracts

    Openserve Fibre

    Openserve Business Fibre
    Uncapped Openserve Business Fibre with speeds up to 500Mbps

  • Coverage Map
  • Contact
  • More
    About Atomic

    Our network, team and company history.

    Blog

    News, product updates and articles.

    Help Docs

    Helpful tips and support guides.

    Referral Program

    Rescue your friends from average internet and save!

    Network Status

    Check for maintenance events and known outages.

    Ultimate Fibre Guide

    Overview of the biggest fibre internet questions.

    On Site Support

    Elevate your network with our expert on-site support.

    Dashboard

    Network dashboard for gamers and techies.

Support
Switch to Atomic
Atomic Logo
Support
Switch to Atomic

Home Fibre Packages 

See All

Asset 1

Octotel Home

Asset 2

Frogfoot Home

Vumatel Home

Openserve Home

Business Fibre Packages 

See All

Asset 1

Octotel Business

Asset 2

Frogfoot Business over FTTH

Vumatel Business

Openserve Business

Support

Network Status

Help Docs

Contact

About Atomic

Coverage Map

Referral Program

On Site Services

Dashboard

Blog

We make fibre epic! 🖖🏻

Frequently Asked Questions

9
  • Openserve Fibre Box Lights
  • Holiday Freeze Period
  • Fibre Frequently Asked Questions
  • VoIP
  • Find your Vumatel Serial Number
  • What the lights on your Fibre Box mean
  • Octotel Fibre Box Lights
  • Frogfoot Fibre Box Lights
  • Vumatel Fibre Box Lights

General Info

8
  • Direct Debits
  • Holiday Freeze Period
  • How Discounts Work
  • Important Extra Guides
  • Change Request
  • Moving Properties
  • Scope of Services
  • Overview of Fibre Troubleshooting

Quick Fibre Guides

7
  • How to Connect your Router
  • How to Report a Problem
  • Loadshedding Tips
  • Network Outages
  • WiFi First Aid
  • Extending Your Wi-Fi
  • Fibre Box First Aid (ONT / CPE)

Fibre Setup Guides

8
  • Frogfoot Installation Guide
  • Octotel Installation Guide
  • Vumatel Installation Guide
  • Octotel Reconnection
  • Vumatel Reconnection
  • Frogfoot Reconnection
  • Openserve Reconnection
  • Openserve Installation Guide

Router and WiFi Guides

8
  • How to wirelessly pair Reyee WiFi mesh routers
  • Connecting IoT devices to WiFi
  • IPTV Buffering
  • How to set up a Tenda Nova Mesh
  • Router Settings For Atomic
  • WiFi First Aid
  • WiFi Consultation
  • Samsung TV Issues

Advanced Guides

13
  • RTMP Streaming Relay
  • How to fix a Bridged Line
  • Configure a PPPoE Login on a Laptop
  • Backup Connectivity – GSM Backup
  • Local Software Mirrors
  • Game Servers
  • DNS and NTP Server Options
  • Cabled Speed Tests
  • iPerf Tests
  • IPv6
  • SMTP Settings
  • Static IPs
  • Packet loss, MTR and Pingplotter

How To Switch ISPs

5
  • Frogfoot ISP Migration
  • Vumatel ISP Migration
  • Octotel ISP Migration
  • How To Switch ISPs
  • Openserve ISP Migration
View Categories
  • Home
  • Docs
  • Advanced Guides
  • iPerf Tests

iPerf Tests

3 min read

Test your Atomic Fibre Line Health with iPerf #

We host an iPerf server on our network for Atomic customers, so if you have a laptop plugged into your Fibre ONT/CPE the only thing between your device and the iPerf server is your Fibre Network Operator. If the iPerf tests show packet loss, we can ask the Fibre Network to investigate.

Slow International with Fast Local Speeds #

When you see slow international speeds while getting fast local speeds, it can be a packet loss problem. Small amounts of packet loss (1%) on your fibre line, will have a big impact on international speeds with higher latency (140ms+), while local speeds with low latency will be fast. The best way to detect this is with an 80% UDP test. See below.

✅ Before proceeding please keep in mind this is advanced troubleshooting, and requires tests to be run through your command prompt.

✅ These tests are only for Atomic Access customers. If your ISP doesn’t have clear steps to test for packet loss, please consider switching to Atomic so we can help.

✅  Make sure you run these tests with a laptop/PC connected directly into the Fibre ONT/CPE, with a Cat5 or Cat6 Ethernet cable and make sure the laptop has a Gigabit Ethernet port. For Openserve customers, you can test in the router or configure PPPoE on the laptop Ethernet port.

How to Install iPerf #

Install iPerf3 on a laptop or PC, version 3.9 or newer.

  • macOS:
    • Install homebrew – https://brew.sh/
    • Install iPerf via homebrew – https://formulae.brew.sh/formula/iperf3
  • Linux: there should be an ‘iperf3’ binary package for your distribution
  • Windows (64-bit):

    • Install a recent version of iPerf: https://github.com/ar51an/iperf3-win-builds
    • Or use an older version: https://www.atomic.co.za/wp-content/uploads/iperf3.9_64.zip
    • Open “Command Prompt”
    • cd into the folder where you downloaded or saved the iPerf package e.g. cd C:\Users\YourUsername\Downloads
    • Run the iPerf commands below, but replace iperf3 with iperf3.exe
  • Windows Subsystem for Linux (WSL): depending on Linux distribution, install ‘iperf3’ package

80% UDP Test – Detect Packet Loss Under Load #

iperf3 -4 -V -t 30 -O 3 -u -b 80M -R -c iperf.atomic.ac -p 3334

iperf3 -4 -V -t 30 -O 3 -u -b 80M -l 1440 -R -c iperf.atomic.ac -p 3334 (for Frogfoot / Calix)

Change ‘-b’ parameter to 80% of your line download speed. To be extra sure you can also run this test in the upload direction by removing the ‘-R’ flag and set ‘-b’ to 80% of your line upload speed.

For Openserve (PPPoE) we suggest 70% of line speed.

For Frogfoot and Vumatel Calix ONTs, please add ‘-l 1440’.

What to Expect #

The iPerf UDP test should run with very little loss – ideally 0% for most intervals. Up to about 0.5% for short intervals is usually ok.

The line speed and fibre type can make a difference. It’s easier to get a low speed AE link to run with zero loss than a high speed GPON link. GPON is a shared medium.

If you notice intervals with high packet loss please open a support ticket. Please include all commands used when you make screenshots of the results.

Maximum Line Speed – TCP Test #

This shows the maximum speed of a single TCP session. The result should be close to your fibre line speed (about 90%).

IPv4 command:

iperf3 -4 -V -t 20 -O 3 -R -c iperf.atomic.ac -p 3334

IPv6 command:

iperf3 -6 -V -t 20 -O 3 -R -c iperf.atomic.ac -p 3334

International – TCP Test #

You can also test from our London based iPerf server to check your international speeds.

NOTE: This test will only work if you are testing from an Atomic IP address.

IPv4 command:

iperf3 -4 -V -t 20 -O 3 -R -c uk1.atomic.ac -p 3334

IPv6 command:

iperf3 -6 -V -t 20 -O 3 -R -c uk1.atomic.ac -p 3334

More international iPerf servers.

TCP Stack Tuning #

Default TCP stacks in desktop PCs can perform badly with high latency and you will not see your full line speed. A Speedtest.net test from Australia will clearly show this. Some ISPs use ‘TCP accelerators’ to get around this problem.

When you find that UDP traffic can be sent without problems at high speeds, but TCP speeds are slow, you may need to adjust your TCP stack on the server and/or client side.

When the TCP send / receive buffers are increased and if the TCP congestion algorithm is set to BBR, the fibre line can usually do full line speeds.

A possible solution could be to do your bigger downloads or uploads from a Linux server, with TCP stack improved.

There are various buffer parameters you can optimise, full details here.

We suggest these config changes on Linux in /etc/sysctl.conf

net.core.rmem_max = 134217728
net.core.wmem_max = 134217728
net.ipv4.tcp_rmem = 4096 87380 134217728
net.ipv4.tcp_wmem = 4096 65536 134217728
net.ipv4.tcp_congestion_control=bbr

After you modify sysctl.conf, run ‘sysctl -p’ to activate.

This should be fine for speeds up to gigabit.

Updated on 25 January 2025
Frogfoot, iPerf, Octotel, Openserve, Packet Loss, Vumatel
Cabled Speed TestsIPv6
Table of Contents
  • Test your Atomic Fibre Line Health with iPerf
  • Slow International with Fast Local Speeds
  • How to Install iPerf
  • 80% UDP Test - Detect Packet Loss Under Load
  • What to Expect
  • Maximum Line Speed - TCP Test
  • International - TCP Test
  • TCP Stack Tuning

About Atomic

Atomic is a Specialist Fibre ISP in Cape Town and the Cape Winelands. Our narrow focus makes us #1 in Google and Hellopeter ratings!

We are Fiercely Independent, Founder-Run and Fibre-Only. Big enough to be Reliable, small enough to be Agile and Friendly. We are Gamer & Techie friendly.

Read our Epic Reviews and Switch to Atomic today!

🏆 Reviews: Google & Hellopeter

Links

    • 🖖 About Atomic
    • 🚦 Network Status
    • 📍 Fibre Coverage Map
    • 📖 Our Blog
    • 🤨 Help Docs
    • 🌍 Ultimate Fibre Internet Guide
    • 🚀 How to Switch ISP
    • 🔋 Fibre During Loadshedding
    • 📶 Wifi Guide For Home Internet
    • 🏎 1Gbps Fibre Internet
    • 🔐 Family DNS Protection
    • 🧪 IPv6 Test
    • 🐣 Telegram Quiz Bot
    • 🏡 Fibre Coverage Areas

Home Fibre

  • 🏠 All Home Fibre
  • 🐙 Octotel Home Fibre
  • 🐸 Frogfoot Home Fibre
  • 🐰 Vumatel Home Fibre
  • 🦎 Openserve Home Fibre
  • 🙌 Referral Program

Business Fibre

  • 🏢 All Business Fibre
  • 🐙 Octotel Business Fibre
  • 🐸 Frogfoot Business Fibre
  • 🐰 Vumatel Business Fibre
  • 🦎 Openserve Business Fibre

Network

  • 🛰️ Atomic Dashboard
  • 🔮 AS328266 Looking Glass

Accounts

  • ↕️ Upgrade, Downgrade, Cancel
  • 🚚 Moving House / Address
  • 🪐 Account Updates

Legal

  • 📃 Terms and Conditions
  • 🎟 Super Fair Usage Policy
  • 🕵️‍♂️ Privacy Policy
Order Fibre
X-twitter Facebook Instagram Linkedin Reddit Youtube Google

Atomic Access® is a registered trademark. Our mission is to provide fast, reliable fibre services with epic support!

© 2018-2025 Atomic (Pty) Ltd.
We make fibre epic! 🖖🏻

Logo KFM best of the Cape FInalist
Cape Made Mark
ISPA Code of Conduct Compliant