Julien Ridoux and Darryl Veitch, University of Melbourne Everyone, and most everything, needs a clock, and computers are no exception. Clocks tend to drift off if left to themselves, however, so it is necessary to bring them to heel periodically through synchronizing to some other reference clock of higher accuracy. An inexpensive and convenient way to do this is over a computer network. Since the early days of the Internet, a system collectively known as NTP (Network Time Protocol) has been used to allow client computers, such as PCs, to connect to other computers (NTP servers) that have high-quality clocks installed in them. Through an exchange of packet timestamps transported in NTP-formatted packets over the network, the PC can use the server clock to correct its own. As the NTP clock software, in particular the ntpd daemon, comes packaged with all major computer operating systems, including Mac OS, Windows, and Linux, it is a remarkably successful technology with a user base on the order of the global computer population.
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