Both ARP and RARP are the network layer protocol. Whenever a host needs to send an IP datagram to another host, the sender requests both the logical address and the physical address of the recipient. Dynamic mapping provides two ARP and RARP protocols. The fundamental difference between ARP and RARP that ARP obtains the physical address of the receiver when supplied with the logical address of the receiver while in RARP when supplied with the physical address of the host, it obtains the logical address of the host from the server.
Let's analyze the other differences between ARP and RARP in the comparison table.
|Complete form||Address resolution protocol.||Reverse Address Resolution Protocol.|
|Basic||Retrieve the physical address of the receiver.||Retrieve the logical address for a computer from the server.|
|Mapping||ARP associates the 32-bit logical address (IP) with the 48-bit physical address.||RARP maps the 48-bit physical address to the 32-bit logical (IP) address.|
Definition of ARP
ARP (Address Resolution Protocol) a network layer protocol. Since ARP is a dynamic mapping protocol, each host in the network knows the logical address of another host. Now, suppose a host has to send the IP datagram to another host. But the IP datagram must be encapsulated in a frame so that it can pass through the physical network between the sender and the receiver. Here, the sender needs the physical address of the receiver in order to identify which recipient the packet belongs to when the packet travels on the physical network.
To retrieve the recipient's physical address, the sender performs the following action.
- The sender sends the ARP query packet over the network which is transmitted to all the other hosts or routers on the network.
- The ARP query package contains the sender's logical and physical address and the recipient's logical address.
- All the host and router that receives the ARP query packet process it, but only the intended recipient identifies its logical address present in the ARP query packet.
- The receiver then sends an ARP reply packet which contains the logical address (IP) and the physical address of the receiver.
- The unicast ARP reply packet directly to the sender whose physical address is present in the ARP query packet.
Definition of RARP
RARP (Reverse Address Resolution Protocol) also a network layer protocol. RARP a TCP / IP protocol that allows any host to obtain its IP address from the server. RARP adapted by the ARP protocol and only in contrast to ARP.
RARP performs the following steps to obtain an IP address from the server.
- The sender transmits the RARP request to all other hosts on the network.
- The RARP request packet contains the physical address of the sender.
- All the host that receives the RARP request packet processes it but only the authorized host that can serve the RARP service responds to the RARP request packet that host known as the RARP server.
- The authorized RARP server replies directly to the requesting host with the RARP reply packet which contains the IP address for the sender.
Obsolete RARP now for two reasons. First, the RARP is using the data link layer transmission service; this means that RARP must be present in every network. Secondly, RARP only provides the IP address, but today the computer also needs other information.
Key differences between ARP and RARP
- The complete form of ARP is the address resolution protocol, while the complete form of RARP is the reverse address resolution protocol.
- The ARP protocol retrieves the physical address of the receiver. On the other hand, the RARP protocol retrieves the logical address (IP) of the protocol.
- ARP associates the 32-bit logical address (IPv4) with a 48-bit physical address of the receiver. On the other hand, RARP associates the 48-bit physical address with the receiver's 32-bit logical address.
RARP has been replaced by BOOTP and DHCP.