GATE CS 2025 Set 1 Q.16: OSI/TCP-IP Layering, Physical Layer and Switching

Identify the ONE CORRECT matching between the OSI layers and their corresponding functionalities as shown.

OSI Layers	Functionalities
(a) Network layer	(I) Packet routing
(b) Transport layer	(II) Framing and error handling
(c) Datalink layer	(III) Host to host communication

(a)-(I), (b)-(II), (c)-(III)

(a)-(I), (b)-(III), (c)-(II)

(a)-(II), (b)-(I), (c)-(III)

(a)-(III), (b)-(II), (c)-(I)

Official answer and solution

Solution

Match each OSI layer with its core responsibility.

(a) Network layer is responsible for logical addressing and packet routing (I) across routers.
(b) Transport layer provides end-to-end / host-to-host (process-to-process) communication (III).
(c) Datalink layer handles link-level framing and error handling (II).

Therefore, the correct matching is (a)-(I), (b)-(III), (c)-(II).

Final answer

Option (B)

The answer is the one in the official GATE answer key. The solution is this site's own explanation.

Paper: GATE 2025 Computer Science and Information Technology - Session 1 (CS1)
Question: 16 of 65
Section: Computer Science and Information Technology

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