Which two sublayers comprise the OSI data link layer?

• A. Physical and Data Link
• B. Network and Transport
• C. MAC and LLC
• D. Session and Presentation

Answer: (C)

Two sublayers make up the OSI data link layer: MAC and LLC. The MAC (Media Access Control) sublayer is responsible for how devices gain access to the shared physical medium, framing data for transmission, and using hardware addresses (MAC addresses) to deliver frames to the right device on a local network. The LLC (Logical Link Control) sublayer sits above MAC and provides a consistent interface to the network layer, multiplexing different network-layer protocols over the same data link, identifying higher-layer protocols via service access points, and offering basic flow and error control. This division lets the data link layer handle the low‑level medium access (MAC) while presenting a uniform interface to the network layer (LLC). The other options reference layers or functions that don’t describe these two sublayers, reinforcing why MAC and LLC are the correct pairing.