Which protocol is responsible for translating an IP address to a link-level MAC address?

The Address Resolution Protocol (ARP) is the correct answer because it specifically functions to map IP addresses—used by the Internet Layer of the OSI model—to MAC (Media Access Control) addresses, which pertain to the Data Link Layer. When a device wants to communicate over a local network to another device using its IP address, it needs to determine the corresponding MAC address. ARP is used to send out requests on the local network, asking who has a specific IP address; the device with that IP responds by providing its MAC address.

This mechanism is essential because, while IP addresses are used for routing packets across networks, communication on the local area network requires the use of MAC addresses. Millions of devices may share the same IP address range, but each device has a unique MAC address. By utilizing ARP, devices can successfully navigate local communication instead of direct routing, resulting in efficient data transmission on Ethernet networks.