CCNA (Cisco Certified Network Associate) Anki Practice Test 2026 - Free Cisco Practice Questions and Study Guide

Layer 2 of the OSI model, known as the Data Link layer, is responsible for node-to-node data transfer and error detection and correction. The Protocol Data Unit (PDU) at this layer is referred to as a frame.

When data is transmitted over a network, it is encapsulated at various layers of the OSI model. At the Data Link layer, the PDU contains essential information such as the source and destination MAC addresses, as well as error-checking information through mechanisms like a Frame Check Sequence (FCS). This ensures that the data can be accurately delivered to the appropriate device on a local network.

The other terms refer to PDUs at different layers of the OSI model. A packet refers to the PDU at Layer 3 (the Network layer), bits are the raw data at Layer 1 (the Physical layer), and a segment represents the PDU at Layer 4 (the Transport layer). Understanding these differences is crucial for grasping how data is structured and transmitted through the OSI model.