Which protocol does a PTP client use for time synchronization?

A Precision Time Protocol (PTP) client uses User Datagram Protocol (UDP) for time synchronization, primarily operating over specific ports designed to facilitate accurate timing communication. The correct choice involves UDP over ports 319 and 320, which are used for the synchronization messages that a PTP client exchanges with its PTP master clock.

PTP is designed to provide high precision synchronization, which is essential in environments where timing needs are critical, such as financial transactions or telecommunication networks. By utilizing UDP, PTP can achieve lower latency and faster transmission times, which are necessary for effective synchronization.

The other options involve protocols or ports that are not associated with PTP. For instance, TCP over port 8080 is typically used for web traffic or proxy servers, and FTP over port 21 is reserved for file transfer protocols. IPv6 over port 80 is related to HTTP traffic rather than time synchronization. Thus, the use of UDP on the specified ports for PTP is the correct context for a PTP client's time synchronization process.