Which port is used by NTP for network time synchronization?

Network Time Protocol (NTP) is essential for synchronizing clocks of computer systems over packet-switched data networks. The specific port that NTP uses for this purpose is UDP port 123. This protocol operates over the User Datagram Protocol (UDP) rather than the Transmission Control Protocol (TCP), which is often used for other types of data transmission where reliability is crucial.

Using UDP allows NTP to efficiently transmit small packets of time synchronization data without the overhead associated with TCP connections, which is important for maintaining accurate time across devices in a network. This efficiency is critical when multiple devices must synchronize their clocks, as it minimizes latency and provides faster synchronization.

The other ports listed correspond to different protocols and services, which do not relate to NTP. For instance, TCP port 22 is commonly used for SSH (Secure Shell), while port 3389 is associated with Remote Desktop Protocol (RDP), and port 445 is used primarily for SMB (Server Message Block) services. None of these ports are involved in time synchronization tasks. Thus, the use of UDP port 123 by NTP is both specific and intentional to accommodate the requirements of precise timekeeping over networks.