Golden Client - Intel NUC with Endpoint

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.

Just like the Time synchronization system, Debian is chosen as the 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 onto a USB stick and create a boot from this USB stick. Several tools are available for performing this step, balena is available on a large number of platforms.

• Installers: https://www.debian.org/distrib/netinst 

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 the 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 keeps the application up to date. The steps below add this repository to the system and next install the software. 

# Add our Excentis Repository to the system.
wget -qO - http://bbdl.excentis.com/repo/public-key.key | sudo apt-key add - 
sudo add-apt-repository "deb [arch=amd64] \
http://bbdl.excentis.com/repo/deb $(lsb_release -cs) main"

# Finally install the Wireless Endpoint
sudo apt-get update
sudo apt-get install byteblower-wireless-endpoint

The following configuration launches the Wireless Endpoint immediately at startup. It defines a systemd service. The contents should be saved to the following file

• /etc/systemd/user/byteblower_wep.service

[Unit]
Description=Sync the Clock on the NIC to improve PTP accuracy

[Service]
User=excentis
ExecStart=byteblower-wireless-endpoint -t <Wi-Fi NIC> <MeetingPoint address>
Restart=always

[Install]
WantedBy=multi-user.target

The above configuration uses two parameters that depend on the actual configuration:

• The name of the Wi-Fi network interface, for example: wlo1. The name can be found with the command ip link.
• The network address of the MeetingPoint.

After saving the above file, the service is enabled with the following command. This ensures that the Wireless Endpoint is launched on each subsequent startup.

• systemd enable byteblower_wep.service

Since the Wireless Endpoint runs in the background, no GUI is launched. To see the current status, you can either of the following command:

• systemctl status byteblower_wep
• journalctl --unit=byteblower_wep --since "1 hour"

The top command prints out the current status, and the bottom one shows the log messages of the last hour.

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, the following two packages are required.

• sudo apt install linuxptp chrony

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.

The timesync is configured in the following file. It needs to be edited as a root user.

• /etc/linuxptp/timemaster.conf

# Configuration file for timemaster

[ntp_server ntp-server.local]
minpoll 4
maxpoll 4

[ptp_domain 5]
interfaces enp0s3

[timemaster]
ntp_program chronyd

[chrony.conf]
include /etc/chrony/chrony.conf

[ptp4l.conf]

[chronyd]
path /usr/sbin/chronyd

[phc2sys]
path /usr/sbin/phc2sys

[ptp4l]
path /usr/sbin/ptp4l

The above configuration has two important configuration parameters:

• The name of the Wired network interface (NIC) to use for the PTP time synchronization. In the above example uses enp0s3. As for the Wi-Fi NIC, the name is found with ip link.
• The domain of the PTP clock. The example uses domain 5. This is the configuration value, it depends on the time-synchronzation setup in the lab.