Which sublayer controls the NIC responsible for sending and receiving data on the physical medium?

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

Answer: (C)

The MAC sublayer is responsible for controlling how the NIC accesses the physical medium to send and receive frames. Within the Data Link layer, MAC handles the actual transmission and reception of data on the wire, including placing frames on the medium, recognizing frame boundaries, and using hardware addressing (MAC addresses) to determine which devices should receive a given frame. It also implements medium-access control methods to manage when a device is allowed to transmit, dealing with contention and collisions in shared Ethernet environments.

The physical sublayer, by contrast, is concerned with the actual signaling—voltages, colors, bit timing, and encoding schemes required to move bits across the medium. The network sublayer sits higher up and handles routing and logical addressing (IP), not the mechanics of data transfer on the wire. The LLC sublayer provides logical link control, such as multiplexing multiple network protocols over the same data link, but it does not handle access to the medium or direct NIC control.