Which OSI layer is responsible for node-to-node data transfer and error detection?

• A. Physical Layer
• B. Data Link Layer
• C. Network Layer
• D. Transport Layer

Answer: (B)

The Data Link Layer is responsible for node-to-node data transfer and error detection. It takes raw bits from the Physical Layer and forms frames for transmission over a single link between two adjacent devices. It provides access control to the shared medium, uses MAC addressing to identify the devices on that link, and includes error detection in each frame (typically with a CRC). If an error is detected, the layer can request retransmission, handling issues on that link.

The Physical Layer just moves bits over the medium, so it doesn’t detect errors. The Network Layer handles routing between networks, not the immediate link. The Transport Layer manages end-to-end delivery and reliability across multiple links, not the node-to-node transfer on a single link.