SSC IMD SA 2017 – Question 159

Which of the following statements is NOT true?

• Framing function is not performed by the data link layer.
• Error control function is not performed by the data link layer.
• Flow control function is not performed by the data link layer.
• Channel linking function is not performed by the data link layer.

Detailed Explanation:

The correct answer is d) Channel linking function is not performed by Data Link Layer (चैनल लिंकिंग कार्य डेटा लिंक लेयर द्वारा नहीं किया जाता है।).

Functions of the Data Link Layer (Layer 2 of OSI):

• Framing: Encapsulates network-layer datagrams into discrete data link frames by adding headers and trailers.
• Flow Control: Regulates the amount of data the sender can transmit to prevent overwhelming a slower receiver.
• Error Control: Detects and corrects bit errors occurring on the physical link using parity, checksums, or CRC, coupled with ARQ protocols.
• Physical Addressing: Appends MAC addresses to direct frames to the correct local network adapter.

Analysis of the Question:

Statements (a), (b), and (c) claim that Framing, Error Control, and Flow Control are NOT performed by the DLL, which are false statements because DLL does perform them. The official SSC IMD answer key identifies option (d) as the intended correct option for this question.