Which protocol and port must be open to synchronize time across network devices?

To synchronize time across network devices, the Network Time Protocol (NTP) is used, which operates over User Datagram Protocol (UDP) on port 123. This protocol is specifically designed to distribute time across various devices in a network, allowing them to synchronize their clocks with a reliable time source.

UDP is preferred for time synchronization because it is a connectionless protocol, which means it has lower latency compared to TCP, making it more suitable for time-sensitive applications. The accurate time is critical for the correct functioning of various services within a network, such as logging, transaction timestamps, and security protocols.

Other options do not relate to time synchronization. For example, TCP on port 80 is used for HTTP traffic, while TCP on port 443 is employed for HTTPS, both of which are protocols related to web traffic. UDP on port 53 is utilized for DNS queries. Thus, only UDP 123 aligns with the needs of time synchronization within a network environment.