Knowledge base:
Timesync configuration on macOS
Posted by Pieter Vandercammen, Last modified by Craig Godbold on 12 October 2022 05:07 PM

This article is intended for those working towards highly accurate latency measurements. For purely functional or even throughput tests, the default macOS configuration is sufficient.

Step 1 disable OS-default time sync

The screen below is reachable from the Settings dialog. Disable "Set date and time automatically". This functionality will be done by Chrony.

Step 2 Install and configure software

We recommend installing Chrony from homebrew. This is a more modern NTP application that incorporates advanced synchronization methods that work better compared to the default ones.

To get started, install

Next configure chrony. To this end create the file  /etc/chrony.conf with following contents.

server <NTP server address> maxpoll 6 iburst

Starting chrony goes as follows.

mkdir /var/run/chrony

The following command allows to check whether the time-sync works:

excentis@macos-bigsur-m1-1 ~ % chronyc sources
MS Name/IP address         Stratum Poll Reach LastRx Last sample
^* debian.lab.byteblower.ex>     2   6   377    59    -22us[  -25us] +/-  495us

The '^*' indicates that the server has been selected as time references. The following statiscs provide more info of the last time sync. 

Starting Wireless Endpoint

The Wireless Endpoint can be used in the same way as before.

The latest binaries are available on the setup pages.

Caveats and Expected performance

  • Avoid using the Wired interface for test traffic.
    Large network loads on this interface introduce delays and make the time-synchronization more difficult.
  • macOS is not a realtime operating system. The OS occasionally adds large (40ms +) delays.

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