Cisco Certified Network Associate (CCNA) Practice Exam

Which layer of the OSI model is responsible for error detection and correction?

1. Application layer

2. Transport layer

3. Network layer

4. Data link layer

The correct answer is: Data link layer

The correct answer is the Data Link layer. This layer, which is the second layer of the OSI model, plays a crucial role in establishing a reliable communication link between directly connected nodes. One of its primary functions is to provide error detection and correction. It achieves error detection using techniques like checksums or cyclic redundancy checks (CRC), which help determine if the data has been corrupted during transmission. When an error is detected, the Data Link layer often initiates corrective measures, such as requesting a retransmission of the data from the sender. This ensures the integrity and reliability of the data being transferred over the network link. Other layers of the OSI model serve different purposes. The Application layer focuses on user interface and application services, the Transport layer manages end-to-end communication and ensures data integrity across a network connection, and the Network layer is responsible for logical addressing and routing of packets. Each layer has its specific functions, but the responsibility for error detection and correction squarely falls on the Data Link layer.