Which protocol operates at the TCP/IP Application layer and is used to transfer files?

• A. FTP
• B. IP
• C. ARP
• D. ICMP

Answer: (A)

Transferring files over a TCP/IP network is handled by an application-layer protocol, and the classic choice for this task is FTP. FTP operates at the Application layer and provides commands and responses that enable users to authenticate and move files between systems. It relies on TCP for reliable delivery, typically using a control connection on port 21 and a separate data connection (port 20 in active mode, or a dynamic port range in passive mode). This combination makes FTP specifically suited for file transfers, including functions like login, listing directories, uploading, and downloading files.

In contrast, the other options play different roles: IP handles addressing and routing at the Network layer, ARP translates IP addresses to MAC addresses on the local network at the Link layer, and ICMP is used for diagnostic and control messages to report issues or test reachability. None of these are designed to transfer files, which is why FTP is the correct choice.