Which protocol is used to synchronize time with a master clock or internet time server?

NTP, or Network Time Protocol, is specifically designed for synchronizing clocks over packet-switched, variable-latency data networks. It allows devices to adjust their internal clocks to match the time provided by a master clock or an internet time server. This synchronization is crucial for many network applications, especially those that require accurate timekeeping for logging events, managing security credentials, and coordinating activities between distributed systems.

NTP operates in a hierarchical system of time sources and can provide precise time adjustments, often down to the millisecond or better, depending on network conditions and the response of the time sources. This capability differentiates it from other protocols like SNTP, which is a simplified version of NTP and lacks some of the sophisticated error checking and adjusting mechanisms.

In contrast, protocols such as SMTP are used for email transmission, while DHCP is responsible for dynamic IP address assignment, making them unsuitable for time synchronization purposes. Thus, NTP's focus on maintaining accurate clock synchronization makes it the correct choice for the question about protocols that synchronize time with a master clock or internet time server.