Network Time Protocol

Manually configuring the time on devices is not scalable.

The manually configured clock will drift, resulting in inaccurate time.

NTP (Network Time Protocol) allows automatic syncing of time over a network.

NTP clients request the time from NTP servers.

A device can be an NTP server and an NTP client at the same time.

NTP allows accuracy of time within ~1 milisecond if the NTP server is in the same LAN, or within ~50 miliseconds if connecting to the NTP server over a WAN/the Internet.

Some NTP servers are 'beter' than orthers. The 'distance' of an NTP server from the original reference clock is called stratum.

NTP uses UDP port 123 to communicate.