Reverse Address Resolution Protocol (RARP) is used by diskless computers so they determine their IP address using the network. When the booting computer sends the broadcast ARP request, it places its own hardware address in both the sending and receiving fields in the encapsulated ARP data packet. The RARP server will fill in the correct sending and receiving IP addresses in its response to the message. This way the booting computer will know its IP address when it gets the message from the RARP server. The RARP message format is very similar to the ARP format.