What uniquely identifies each device connected to the Internet?

An IP address uniquely identifies each device connected to the Internet. It serves as a crucial part of the Internet Protocol, which is responsible for routing packets of data from one device to another. By assigning a unique IP address to every device, the network can effectively direct the flow of information, distinguishing one device from another across the vast interconnected web.

The reason the IP address is the correct choice in this context is that it directly participates in the communication process on the Internet, enabling devices to locate and communicate with each other. The format of the IP address (whether IPv4 or IPv6) reflects this uniqueness, where each number or sequence in the address helps specify the exact device within the entire network, ensuring accurate data transfer.

Other identifiers mentioned, such as a MAC address, while unique to each device on a local network and important for data link layer communication, do not serve the same global function as an IP address. Similarly, network names and host names are more about the identification or labeling of a device or network rather than providing a unique routing address on the Internet.