In the following pairs of OSI protocol layer/sub-layer and its functionality,…
2014
In the following pairs of OSI protocol layer/sub-layer and its functionality, the INCORRECT pair is
- A.
Network layer and Routing
- B.
Data Link Layer and Bit synchronization
- C.
Transport layer and End-to-end process communication
- D.
Medium Access Control sub-layer and Channel sharing
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Correct answer: B
Answer: The incorrect pair is "Data Link Layer and Bit synchronization."
Why this is incorrect:
Bit synchronization belongs to the Physical layer because it involves the timing, encoding, and transmission of individual bits on the medium.
The Data Link layer is responsible for framing, error detection/correction at the link level, flow control between adjacent nodes, and medium access control (at the MAC sub-layer), not bit-level timing.
Correct mappings for the other pairs:
Network layer — routing: selects paths and forwards packets between networks.
Transport layer — end-to-end process communication: provides process-to-process connections, reliability, and multiplexing (examples: TCP, UDP).
MAC sub-layer — channel sharing: manages access to the shared physical medium (e.g., CSMA/CD, CSMA/CA).
Summary:
The incorrect pairing is the one that assigns a Physical-layer function (bit synchronization) to the Data Link layer.