Question

Which of the following ports is used by FTP? (2)

a) UDP/21
b) UDP/69
c) TCP/21
d) UDP/20

Answer 1

FTP (File Transfer Protocol) primarily operates over TCP (Transmission Control Protocol) on port 21. Thus correct option is c) TCP/21

Step-by-step explanation:

FTP (File Transfer Protocol) primarily operates over TCP (Transmission Control Protocol) on port 21. TCP is a connection-oriented protocol that ensures reliable and ordered delivery of data between devices. Port 21 is the standard port dedicated to FTP's control channel, managing commands and responses between the client and server during the file transfer process.

FTP follows a client-server model where the client initiates a connection to the server on port 21 to establish control. This port handles the authentication, commands, and initial setup for data transfer. However, the actual file transfer occurs over a different port, often dynamically chosen by the server (commonly port 20 for data transfer). TCP, being a reliable and connection-based protocol, ensures that data sent over port 21 is received accurately and in the correct order, crucial for the integrity of file transfer operations.

In networking, the choice of ports and protocols is critical for effective communication between devices. In the case of FTP, TCP on port 21 serves as the primary means of control, allowing clients to authenticate, send commands, and manage the file transfer process with reliability and orderliness. Understanding the specific port and protocol used by FTP is essential for configuring firewalls, routing, and ensuring the secure and efficient transfer of files across networks.

Answer 2

FTP uses the TCP/21 port for its command channel. This protocol ensures reliable transmission of data, essential for transferring files. The data channel typically uses TCP/20. Option c is correct.

Step-by-step explanation:

The port used by FTP is TCP/21. FTP, which stands for File Transfer Protocol, primarily uses the TCP protocol rather than UDP because it requires reliable data transmission.

FTP uses two primary channels for communication: a command channel, which utilizes port 21, and a data channel, which typically uses port 20.

Each time an FTP connection is established, the command channel is created using TCP/21 to send control information, such as user authentication and commands to upload or download files.

The data channel often set up on TCP/20 is used to actually transfer the files. It's important to remember that FTP is built on top of the TCP protocol because it ensures ordered and reliable delivery of packets, which is crucial for file transfers.

Option c is correct.