Which sublayer provides a mechanism to allow multiple devices to communicate over a shared medium?

• A. MAC sublayer
• B. LLC sublayer
• C. Physical sublayer
• D. Network sublayer

Answer: (A)

Sharing a single communication channel among many devices is handled by the MAC sublayer at the data link layer. The MAC sublayer controls how devices access the shared medium and how frames are delivered to the correct destination on that local link. In traditional Ethernet, it uses mechanisms like CSMA/CD to listen before transmitting and to detect collisions, coordinating access so multiple devices can share the same wire. It also uses MAC addresses to identify devices on the same segment.

The LLC sublayer above it deals with multiplexing higher-layer protocols and provides basic error handling, but it doesn’t manage access to the physical medium. The Physical sublayer is concerned with the actual signaling and hardware transmission, while the Network sublayer (Layer 3) handles routing and logical addressing across networks.