GATE CS 2014 Set 3 Q.33 (CS Q.23): OSI/TCP-IP Layering, Physical Layer and Switching

In the following pairs of OSI protocol layer/sub-layer and its functionality, the INCORRECT pair is

Network layer and Routing

Data Link Layer and Bit synchronization

Transport layer and End-to-end process communication

Medium Access Control sub-layer and Channel sharing

Official answer and solution

Solution

Verify each OSI layer pairing against its standardized functionalities to identify the incorrect pair.

Option A (Network layer and Routing):
The Network layer is responsible for logical addressing (IP addresses), packet forwarding, and path determination (routing). This pairing is CORRECT.
Option B (Data Link Layer and Bit synchronization):
Bit synchronization deals with clock timing, bit duration, and synchronizing sender and receiver clocks at the bit level. This is a fundamental function of the Physical layer, not the Data Link layer. (The Data Link layer is responsible for frame synchronization/framing, MAC addressing, error detection, and flow control). Hence, this pairing is INCORRECT.
Option C (Transport layer and End-to-end process communication):
The Transport layer provides process-to-process (end-to-end) delivery of messages using port numbers, flow control, and error recovery (e.g., TCP/UDP). This pairing is CORRECT.
Option D (MAC sub-layer and Channel sharing):
The Medium Access Control (MAC) sub-layer of the Data Link layer coordinates multiple stations sharing a common physical transmission medium (channel sharing/multiple access protocols like CSMA/CD, ALOHA). This pairing is CORRECT.

Therefore, the incorrect pair is B.

Final answer

Common trap

Confusing bit synchronization (Physical layer) with frame synchronization (Data Link layer).

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

GATE questions are the work of the organising institutes. This site is independent and is not affiliated with them.