The protocol is highly accurate, using a resolution of less than a nanosecond (about 2^-32 seconds). Having available several time sources, NTP can select the best candidates to build its estimate of the current time.

Propagating time from one node to another form a hierarchical graph with reference clocks at the top. Each node of such a network can exchange time information either bi-directional or unidirectional. NTP is highly scalable: A synchronization network may consist of several reference clocks.Temporarily or permanently insane time sources will be detected and avoided. Multiple candidates can be combined to minimize the accumulated error. NTP is a fault-tolerant protocol that will automatically select the best of several available time sources to synchronise to.(It will not just make all systems agree on some time, but will make them agree upon the true time as defined by some standard.) All clocks are set towards that true time. NTP needs a reference clock that defines the true time.For example, database systems using transactions and crash recovery like to know the time of the last good state. Just imagine some e-mail message arriving five minutes before it was sent.Įven on a single computer some applications have trouble when the time jumps backwards. Isolated networks may run their own incorrect time, but as soon as you connect to the Internet, effects will be visible. Switching between these systems would cause time to jump forward and back, producing an undesirable effect. Obviously, if one system is ahead of the others, the others are behind that particular one. However, if you have communicating programs running on different computers, time should uniformly advance if you switch from one computer to another. Why Should Computer Time be synchronised? SNTP (Simple Network Time Protocol) is basically NTP, but lacks some internal algorithms that are not needed for all types of servers. NTP is an Internet standard protocol originally developed by Professor David L. NTP stands for Network Time Protocol, and it is an Internet protocol used to synchronise the clocks of computers to some time reference. Only 28% of the internet based stratum 1 clocks actually appears to be useful, based on research by Nelson Minar, MIT Media Lab Cambridge, MA USA.

Incredibly, one time source was offset by a staggering 6 years.

A reported 391 of 957 supposedly stratum 1 NTP time sources had time offsets of over 10 seconds. Recent studies show an alarming number of stratum 1 time sources on the internet are bad time keepers. The time source used by the NTP time server is extremely important as this forms the basis of all time updates across the network. A time server is utilised to obtain the correct time from a time source and adjust the local time in each participating computer. Network Time Protocol can be utilised to synchronise the time on computers across a network. Typically, NTP provides accuracies of between 1 and 50 milliseconds depending on the time source and network paths. NTP provides the ability to access time services, organise the time synchronisation subnet and adjust the local clock in each participating subnet computer. NTP is widely used to synchronise the time on computers on the internet. About NTP Network Time Protocol, Time Servers and Sychronised Time

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