The NTP synchronizes the system time on a computer with that of an Internet Time Server that has been synchronized to a reference source such as radio, Global Positioning Service (GPS) receiver that provides Coordinated Universal Time (UTC). NTP communicates with the Internet Time Server by using a dialup modem or direct LAN connection.

The SNTP is a basic version of NTP that allows for a greater degree of error, but can still deliver time to an accuracy on the order of fractions of a second.