Installing a low-latency Wireless Endpoint (Golden client)
Posted by Pieter Vandercammen, Last modified by Craig Godbold on 12 October 2022 05:06 PM
This article focuses on the ideal setup to measure the latency of a network. More so than functional or even throughput testing, this type of test requires special care for proper time synchronization between a ByteBlower Endpoint and ByteBlower server.
To ensure this sync, we recommend the setup as shown in the picture below. From left to right we see the "ByteBlower Server", the device under test (a Wi-Fi Access Point) and the ByteBlower Endpoint ('Golden Client'). The network switch at the bottom of the image is used only to connect the management interfaces.
Two types of network traffic flow through this setup
In the above image, both the ByteBlower server and Golden Client are synchronized to a common reference clock. This enables accurate latency measurements.
The Golden client
The golden client is the reference system for performing latency measurements with the Wireless Endpoint. In the sections below describe how to install Linux, Wireless Endpoints and configure the PTP-timesync.
Installing the OS
Just like the Time synchronization system, Debian is chosen as base OS for the Golden client. It's a popular Linux distribution with a long history that will stay relevant for the time being. The guide below has been tested on Debian 10.
The ISO image for the Linux installer is available from the link below. A common approach is to copy this binary on onto a USB stick and create boot from this USB stick. Several tools are available for performing this step, balena is one that is available on a large number of platforms.
This Low latency WEP client does not require a desktop environment. If you’re comfortable with managing such a headless system, the desktop can be omitted. For Intel NUC platform both headless and desktop should work well, no large performance differences are expected.
Installing the Wireless Endpoint
The wireless Endpoint is available in the Excentis repository. Adding this repository to the system makes it keep the application up to date. The steps below add this repository to the system and next install the software.
The following configuration launches the Wireless Endpoint immediately at startup. It defines a systemd service. The contents should be saved to following file
The above configuration uses two parameters that depend on the actual configuration:
After saving the above file, the service is enabled with the following command. This is ensures that the Wireless Endpoint is launched on each subsequent startup.
Since the Wireless Endpoint runs in the background, no GUI is launched. To see the current status, you can either of the following command:
The top command prints out the current status, the bottom one show the log messages of the last hour.
PTP on Golden client
As detailed at the start, it is important for the ByteBlower server and Wireless Endpoint to be synchronized to the same time-reference. On local networks one can use the Precision-Time-Protocol. This offers the most reliable time-sync.
To configure PTP on Linux, following two packages are required.
LinuxPTP takes care of the PTP configuration. Chrony organizes the overall time synchronization. In case when the PTP clock becomes unavailable it will fall back to other time sources.
Configuring the timesync software
The timesync is configured in the following file. It needs to be edited as a root user.
The above configuration has two important configuration parameters:
This timesmaster is enabled with
When all goes well,
In addition to the above, more information about the actual timesync is available with
Example Test results
The results below show example results attainable with the Wireless Endpoint and a proper Time Synchronization master. It contains the latency results between the same two hosts, Golden Client to a ByteBlower 4100, but over different media