What is the primary communication method for NTP?

• A. Transmission Control Protocol (TCP) on port 80.
• B. User Datagram Protocol (UDP) on port 123.
• C. Stream Control Transmission Protocol (SCTP) on port 123.
• D. ICMP Echo on port 0.

Answer: (B)

Time synchronization thrives on fast, small exchanges rather than establishing a full connection. NTP uses UDP on port 123 because UDP provides a lightweight, connectionless datagram service ideal for sending time-stamped messages quickly. This low overhead keeps latency low, and NTP’s own algorithms handle clock offset and delay even when some packets are lost, so guaranteed delivery isn’t required. The other options point to protocols or ports not used for NTP (TCP on port 80, SCTP on 123, or ICMP Echo), so UDP on port 123 is the correct primary communication method.