Overview of Network Time Protocol (NTP)

Networked computers share resources such as files. These shared resources often have time-stamps associated with them so it is important that computers communicating over networks, including the Internet, are synchronized. The Network Time Protocol (NTP) is an Internet Standard Recommended Protocol for communicating the Coordinated Universal Time (UTC) from special servers called time servers and synchronising computer clocks on an IP network.

The NTP daemon can not only adjust its own computer's system time. Additionally, each daemon can be a client, server, or peer for other NTP daemons:
- As client it queries the reference time from one or more servers.
- As server it makes its own time available as reference time for other clients.
As peer it compares its system time to other peers until all the peers finally agree about the "true" time to synchchronize to.

Clock Strategy

NTP uses a hierarchical, semi-layered system of levels of clock sources, each level of this hierarchy is termed a stratum and assigned a layer number starting with 0 (zero) at the top. The stratum level defines its distance from the reference clock and exists to prevent cyclical dependencies in the hierarchy.

Importance of NTP

In a commercial environment, accurate time stamps are essential to everything from maintaining and troubleshooting equipment and forensic analysis of distributed attacks, to resolving disputes among parties contesting a commercially valuable time-sensitive transaction.
In a programming environment, time stamps are usually used to determine what bits of code need to be rebuilt as part of a dependency checking process as they relate to other bits of code and the time stamps on them, and without good time stamps your entire development process can be brought to a complete standstill.
So, time is inherently important to the function of routers and networks. It provides the only frame of reference between all devices on the network. This makes synchronized time extremely important and this is where Network Time Protocol comes into picture.

Supported Platforms

NTP's native operating system is UNIX. Today, however, NTP runs under many UNIX-like systems. NTP v4 has also been ported to Windows and can be used under Windows NT, Windows 2000, and newer Windows versions up to Windows Vista and Windows 7.
The standard NTP distribution can not be run under Windows 9x/ME because there are some kernel features missing which are required for precision time keeping.