File Transfer Protocol (FTP) and Simple Mail Transfer Protocol (SMTP) work at which layer in the Open Systems Interconnection (OSI) model?
A. the Session layer
B. the Presentation layer
C. the Application layer
D. the Network layer
Correct Answer: C
Explanation:
FTP and SMTP work at the application layer in the OSI model. The application layer is responsible for interacting directly with the application. It provides application services, such as e-mail and FTP. The following protocols work on the application layer:
– FTP: Used to transfer data between hosts through the Internet or a network.
– SMTP: A Transmission Control Protocol (TCP)/ Internet Protocol (IP) protocol used to send and receive e-mail messages.
– Telnet: Used to allow remote logins and command execution.
The Session layer is incorrect because this layer creates, manages, and terminates sessions between communicating nodes. NetBIOS and Session Control Protocol (SCP) work at the session layer.
The Presentation layer is incorrect because this layer enables coding and conversion functions for application layer data. The Presentation layer includes graphic image formats, such as Graphics Interchange Format (GIF), Joint Photographic Experts Group (JPEG), and Tagged Image File Format (TIFF).
The Network layer is incorrect because this layer defines the network address or the Internet Protocol (IP) address, which are then used by the routers to make forwarding decisions.