NTP (Network Time Protocol) primarily uses UDP port 123.
Detailed Explanation:
NTP relies on the User Datagram Protocol (UDP) for its operations. Specifically, it uses port 123 for both sending and receiving time synchronization data. This port is used by both the NTP server and the NTP client.
- NTP Server: Listens on UDP port 123 for incoming time synchronization requests from clients. It responds to these requests with the current time information.
- NTP Client: Initiates time synchronization requests to the NTP server using UDP port 123. The client might use a high-numbered ephemeral port as the source port for its outgoing requests, but the destination port is always 123 on the NTP server.
It's worth noting that while NTP primarily uses UDP port 123, sometimes clients may use source ports above 1023. However, the critical point is that the server is listening on and communicating via UDP port 123.
Because NTP is a legacy protocol, it has been subject to various security vulnerabilities over the years. This highlights the importance of keeping NTP implementations up-to-date and properly configured.
