Which layer of the TCP/IP model corresponds to the OSI session and presentation layers?

• A. The Transport layer maps to OSI Session, Presentation, and Application layers.
• B. The Application layer maps to OSI Session, Presentation, and Application layers.
• C. The Internet layer maps to OSI Session, Presentation, and Application layers.
• D. The Data Link layer maps to OSI Session, Presentation, and Application layers.

Answer: (B)

The TCP/IP Application layer is responsible for high-level protocols and services that include how data is presented and how user applications interact, which in OSI is handled by the session, presentation, and application layers. Since TCP/IP does not have separate session or presentation layers, those functions are folded into the Application layer along with the application protocols themselves (like HTTP, FTP, SMTP, and even encryption or data encoding handled by TLS within applications). In contrast, the Transport layer provides end-to-end delivery services, the Internet layer handles routing and addressing, and the Data Link layer manages node-to-node communication. That consolidation is why the Application layer best maps to OSI’s session, presentation, and application layers.