The
Network Time Protocol (
NTP) is a protocol for distributing the
Coordinated Universal Time (UTC) by means of
synchronizing the clocks of computer systems over
packet-switched, variable-
latency data networks. NTP uses
UDP port 123 as its
transport layer. It is designed particularly to resist the effects of variable latency by using a
jitter buffer.
NTP is one of the oldest Internet protocols still in use (since before 1985). NTP was originally designed by Dave Mills of the University of Delaware, who still maintains it, along with a team of volunteers.
NTP is not related to the much simpler DAYTIME (RFC 867) and TIME (RFC 868) protocols.
NTP uses Marzullo's algorithm with the UTC time scale, including support for features such as leap seconds. NTPv4 can usually maintain time to within 10 milliseconds (1/100&_160;s) over the public Internet, and can achieve accuracies of 200 microseconds (1/5000&_160;s) or better in local area networks under ideal conditions.
