Which protocol automatically assigns IP addresses to devices on a network?

Dynamic Host Configuration Protocol (DHCP) is the correct answer because it is specifically designed to automatically assign IP addresses and other network configuration details, such as subnet masks and default gateways, to devices on a network. This process allows devices to connect to the network without the need for manual configuration, streamlining network management significantly.

When a device connects to a network, it sends a request for an IP address. The DHCP server receives the request and allocates an available IP address from a defined range, which is known as a DHCP scope. The server then communicates back to the device with its new IP address and other relevant information, allowing the device to communicate over the network without any intervention from an administrator.

The other choices do not perform this function. Network Address Translation (NAT) is used to modify the IP address information in IP packet headers while they are in transit across a traffic routing device, primarily to allow multiple devices on a local network to be mapped to a single public IP address. A firewall is a security device that monitors and controls incoming and outgoing network traffic based on predetermined security rules. Internet Control Message Protocol (ICMP) is used for error messages and operational information exchange, such as ping operations, but does not involve IP address assignment.