About NTP
What is NTP?
NTP stands for Network Time Protocol. NTP is the most important and widely-used protocol that is used to synchronize computer clock times in a network of computers to a time reference. NTP uses Coordinated Universal Time (UTC) to synchronize computer clock times to a millisecond or even a fraction of a millisecond.
The term NTP applies to both the protocol and the server/client programs.
NTP is a highly scalable and fault-tolerant protocol. It automatically corrects for leap seconds. And even when a network connection is temporarily unavailable, NTP can use measurements from the past to estimate current time and error better than a computer by itself.
Why should time be synchronized?
Time should only ever advance. However, PC’s are notorious for their time drift, because they are only equipped with a real time clock (RTC) where the time is set manually and can drift drastically.
If you have communicating programs running on different computers, time still should advance even if you switch from one computer to another. Obviously if one system is ahead of the others, the others are behind that particular one. From the perspective of an external observer, switching between these systems would cause time to jump forward and back.
As a consequence, isolated networks may run their own wrong time, but as soon as you connect to the Internet, effects will be visible. Just imagine an email message arrived five minutes before it was sent, and there even was a reply two minutes before the message was sent.
Even on a single computer some applications have trouble when the time jumps backwards.
Servers versus Clients
The NTP program/protocol is utilized by NTP Servers and NTP Clients.
Servers - The NTP Server references a “true time” source and outputs the NTP time code. An NTP server can reference either 1) an NTP Server via the Internet 2) GPS-based time or 3) any other time code being generated by a master clock such as IRIG, SMPTE/EBU, etc. The most common true time source is a GPS Master Clock like ESE's ES-185U/NTP: GPS Master Clock/ NTP Time Server.
The NTP Server then uses that time input and the NTP protocol to output NTP time code, which as described above is highly accurate and reliable, but most importantly it can be interpreted by computers and hardware on a network and maintain that accuracy for many important applications.
Clients - The NTP client (NTP-C) initiates a request for time to the NTP server, and it can decode and output the time given by the server in a chosen time zone while maintaining the high level of accuracy defined by the protocol. One example of an NTP Client is ESE's ES-993U/NTP-C: Time Code Remote Display. ESE offers the option of NTP Client (NTP-C) on some 4-digit and 6-digit displays, so you can synchronize your time displays with your network rather than another time code.
Conclusion: The most accurate and reliable method for synchronizing all the clocks on your network is with an NTP Time Server.