Answer:
TCP
Explanation:
FTP (File Transfer Protocol) can be found in the Application layer of the TCP/IP model and the Application layer of the OSI model not on the Transport layer of the TCP/IP model as stated in the question.
In the Transport layer, we have end-to-end message transmission or application connection, which can be grouped as connection-oriented or connectionless. Connection-oriented is implemented in TCP (Transmission Control Protocol) while connectionless is implemented in UDP (User Datagram Protocol), which are the two major protocols found in the Transport Layer of the TCP/IP model. The choice of TCP as the correction option out of the four options given is based on the fact that FTP is a protocol found in the Application layer of TCP/IP
FTP is a network protocol used to receive and send files between machines on a TCP/IP network using ports 20 and 21. This protocol uses a client-server architecture, an FTP client is installed on the client and used to establish the connection to an FTP server running on a remote machine. FTP supports user authentication, so when a connection has been established and the user authenticated, data can be transferred between them. All data are sent in clear text, be it usernames or passwords. For secure transmission that protects the username and password, and encrypts the content, FTP can be secured with SSL.TLS or replaced with SSH File Transfer Protocol (SFTP). A connection to port 21 from the FTP client forms the control stream on which commands are passed to the FTP server and responses are collected. The parameters for the data streams depend on the specifically requested transport mode. Data connection usually uses port 20.
