How many sub-layers does the Data Link Layer have?

How many sub-layers does the Data Link Layer have?

• A. Two
• B. One
• C. Three
• D. Four

Answer: (A)

The Data Link Layer is split into two sublayers to separate different responsibilities at this layer. The lower sublayer, MAC (Media Access Control), handles how devices actually access and use the physical medium. It takes care of frame creation, addressing at the hardware level (MAC addresses), and controlling access to the shared medium, including error detection within frames. The upper sublayer, LLC (Logical Link Control), sits above MAC and provides a consistent interface to the Network Layer. It multiplexes different network-layer protocols over the same data link and offers services like flow control and, where supported, error notification to the network layer. By dividing these duties, the Data Link Layer can effectively manage both the mechanics of transmission and the interface to higher-level protocols, yielding two sublayers.

The Data Link Layer is split into two sublayers to separate different responsibilities at this layer. The lower sublayer, MAC (Media Access Control), handles how devices actually access and use the physical medium. It takes care of frame creation, addressing at the hardware level (MAC addresses), and controlling access to the shared medium, including error detection within frames. The upper sublayer, LLC (Logical Link Control), sits above MAC and provides a consistent interface to the Network Layer. It multiplexes different network-layer protocols over the same data link and offers services like flow control and, where supported, error notification to the network layer. By dividing these duties, the Data Link Layer can effectively manage both the mechanics of transmission and the interface to higher-level protocols, yielding two sublayers.