Dr. David Mills from the University of Delaware realized the need for a synchronization tool and developed the Network Time Protocol (NTP). Although it is not the first and only time synchronization protocol, it is the most widely used and probably owes its success, to the now Professor Mills, and his dedicated team for its continuous development. What started as a protocol that could manage synchronization to a few milliseconds is now able to keep computer clocks within a few nanoseconds of each other (milli = 1 / thousandth nano = 1 / billionth).
NTP is hierarchical and divided into layers. A clock source is called Stratum 0, while an NTP server is Stratum 1, computers and devices that receive the time from a Stratum 1 server become Stratum 2, and so on. This hierarchical structure means that tens of thousands of devices can be synchronized at the same time without flooding the NTP server or network bandwidth. NTP servers are based on the use of a reference clock. While this can be anything from a wristwatch to a computer system clock, it would not make sense to use a reference clock that is not accurate to itself Most networks using an NTP server use a UTC time source . You can get more blog posts from our Oracle DBA Tutorials and youtube channel.
UTC or Coordinated Universal Time is based on the time reported by incredibly accurate and expensive atomic clocks. The time signals of an atomic clock can be collected, either through the Internet (although the accuracy is variable and depends on the distance), special radio broadcasts broadcast in various countries (including the US, UK , Germany, France and Japan) or through the American GPS (Global Positioning System).
NTP servers distribute this Stratum 0 time source among all devices on the network that connect to the NTP server. NTP will then advance or hold the system clock to match the timing reference. NTP also has built-in security measures called authentication. It is a set of encrypted keys that are used to identify both the client and the server. Unfortunately authentication is not available in internet time references and that is why both Microsoft and Novell suggest that hardware sources be used as a synchronization reference. NTP is currently on version 4 with version 5 under development and is open source and freely available for download via ntp website...