The Application Layer Protocols of the TCP/IP Suite
Now that you have an understanding of how the network and transport layers of the TCP/IP suite function, take a look at the application layer protocols and services that make the network useful.
The following sections outline the major application protocols.
File Transfer Protocol (FTP) is used to exchange data between two undefined hosts. FTP is uninterested in the types of hosts exchanging data. Two TCP connections, ftp- control (TCP port 21) and ftp-data (TCP port 20), are used to perform the data exchange. FTP uses a host-authenticated interactive client/server model. The client connects to the known ports, and the server establishes the session(s) on the client's requesting port address. ...