ballestr/gpstime

Tools and explorations on GPS and NTP

gpstime

Tools and explorations on GPS and NTP.

Goal: build an NTP source that has a precision better than 1ms, all the time.

• 1ms is not a particularly difficult goal in itself
• but doing it reliably, in presence of network or GPS signal loss requires some careful thinking and testing
• and this needs to be demonstrable, requiring proper monitoring, metrics, alerts
• and finally, what are actually the benchmark references that are reliably precise to better than 1ms, from a random internet endpoint?

See also https://github.com/ballestr/chronyd_exporter

Important stuff

• Have good GPS antenna reception
• Use Pulse Per Second
• Use dedicated hardware

Install

# git clone https://github.com/ballestr/gpstime.git /opt/gpstime
# /opt/gpstime/hw_sbc/install.hwsbc.sh

basics

• https://en.wikipedia.org/wiki/Network_Time_Protocol
• https://opensource.com/article/18/12/manage-ntp-chrony
• https://www.ntppool.org/join/configuration.html Configuration recommendations for servers joining the pool
• NTP Pools
  • https://www.ntppool.org/zone/europe
  • https://services.renater.fr/ntp/serveurs_francais
• https://questions.ntp.narkive.com/bKcPTXXY/ntp-how-to-measure-the-quality-of-ntp-server

Metrics

• https://www.chrony.eu/status/1-pool

Reference time servers

• CH: https://www.metas.ch/metas/en/home/fabe/zeit-und-frequenz/time-dissemination.html