Which Layer-4 Protocol and port match FTP?

File Transfer Protocol (FTP) is primarily utilized for the transfer of files over a network and operates at Layer 4 of the OSI model, which is the Transport Layer. The correct matching for FTP involves two specific ports: TCP port 21 is used for the control connection, where commands and responses are exchanged, while TCP port 20 is designated for the data connection that handles the actual file transfers.

Using TCP for both connections is crucial because it provides reliable, ordered, and error-checked delivery, which is essential for transferring files without corruption or loss. Unlike UDP, TCP establishes a connection and ensures that all packets are delivered properly, making it ideal for applications like FTP that require validated transfer of data.

Having both the control and data transfer utilize TCP ensures that FTP can effectively manage file transfers and handle potential issues like packet loss, which is not something UDP would guarantee. Thus, the correct choice highlights the use of TCP for both necessary ports in the FTP protocol.