Which protocol operates at the network layer?

The correct answer indicates that both ARP (Address Resolution Protocol) and ICMP (Internet Control Message Protocol) operate at the network layer, which is consistent with their respective functions and the OSI (Open Systems Interconnection) model.

ARP operates at the network layer because its primary function is to map a known IP address to a MAC address, which is essential for devices on a local network to communicate over Ethernet. It facilitates the communication between different network layers by allowing the delivery of packets on a local network, thereby enabling devices to find each other and send messages.

ICMP, on the other hand, serves a different purpose at the network layer, primarily dealing with error messages and operational information related to IP processing. It is used for reporting errors, performing network diagnostics (like using the ping command), and assisting in the flow of data packets through the network by sending control messages.

Both protocols play crucial roles in the functioning and management of IP networks, emphasizing important network layer functionalities, such as address resolution and error reporting. This understanding solidifies why both are categorized as operating at the network layer.