Which protocol is commonly used for network time synchronization?

The Network Time Protocol (NTP) is widely used for synchronizing clocks of computer systems over packet-switched, variable-latency data networks. NTP is essential because accurate timekeeping is crucial for many applications, including logging events, running time-sensitive applications, and maintaining security protocols that rely on timestamped data.

NTP operates by allowing devices to synchronize their internal clocks to a reference time source, usually one of several time servers that may be connected to atomic clocks or GPS signals to ensure high accuracy. Through a hierarchical system of time sources, NTP can distribute time information effectively across a large network, maintaining synchronization accuracy in the millisecond range.

Other protocols mentioned do not serve this purpose; for example, HTTP is designed for transmitting hypertext documents, FTP facilitates transferring files between client and server, and SMTP is used for sending email messages. Each of these protocols has its specific context and application, but none is intended for synchronizing time across networks.