Explain how the FTP protocol transfers files over a network.

The FTP protocol transfers files over a network by establishing a connection between the client and server for data exchange.

FTP, or File Transfer Protocol, is a standard network protocol used for the transfer of computer files between a client and server on a computer network. It is built on a client-server model architecture and uses separate control and data connections between the client and the server. This is known as a dual connection, which is a defining characteristic of the FTP protocol.

When a file transfer is initiated, the client connects to the server to establish the main control connection. Once this connection is established, the client can send commands to the server to access directories, list files, and perform other operations. The server responds to these commands over the same control connection, providing feedback to the client about the status of the operations.

For the actual file transfer to take place, a separate data connection is established. This is done in one of two ways: active mode or passive mode. In active mode, the server initiates the data connection to the client. In passive mode, it's the client that initiates the data connection to the server. The choice between active and passive mode can be determined by factors such as firewall rules and network configuration.

Once the data connection is established, the file transfer begins. The FTP protocol supports both binary and ASCII transfer modes, allowing for the transfer of both text and binary files. The client can also specify the desired file transfer type before initiating the transfer.

After the file transfer is complete, the data connection is closed, but the control connection remains open for further commands. The client can then initiate additional file transfers, or close the control connection to end the FTP session.

In summary, the FTP protocol transfers files over a network by establishing a dual connection between the client and server, using one connection for control commands and responses, and a separate connection for the actual file transfer. This allows for efficient and flexible file transfers over a network.