reverse address resolution protocol (IP) (RARP)
Each computer connected to a TCP/ IP network must have a unique IP address, otherwise it cannot participate in the communication. Generally, the IP address is assigned during installation and stored in the corresponding memory location. Since this is not possible with diskless workstations because these machines do not have a corresponding memory location, mechanisms have been developed to resolve the assignment of IP addresses when connecting corresponding devices to the network.
The Reverse Address Resolution Protocol (RARP) is a protocol for dynamic allocation of IP addresses in addition to the bootstrap protocol and the Dynamic Host Configuration Protocol( DHCP).
The Reverse Address Resolution Protocol (RARP) is thus used to assign an IP address to a diskless workstation. Since network-wide communication is not possible without an IP address, the station connected to a network must obtain an IP address from another computer, the RARP server. To do this, the client willing to send communicates with the RARP server, which manages all Internet addresses for harddiskless stations. For this purpose, a request is sent from the client to the server. This RARP request is packaged in an Ethernet frame and identified in the type field as a RARP data packet. The request is sent as a broadcast over the network and thus goes to all connected computers. The broadcast contains the hardware address of the client. The RARP server responds to the RARP client's request and, based on the physical address of the requesting station, assigns an IP address stored in a table, using the client's hardware address as the destination address. If there are multiple RARP servers on the network, then the RARP client uses the first received response with the transmitted IP address.
Any network that has stations connected to it without a hard disk and that supports the RARP protocol must have a RARP server. The RARP operates at the network layer and is derived from the Address Resolution Protocol( ARP) and therefore uses a similar data format. It dates from 1984 and is described in RFC 903.