Address
Resolution Protocol ARP and RARP
IP addresses are assigned independently of the hardware
addresses of the machines. To send a datagram on the Internet, the
network software must convert the IP address into a physical address, used to
transmit the frame.
Address resolution refers to the determination of the
address of a device from the address of that equipment to another protocol level.
We solve, for example, an IP address in an Ethernet address or an ATM address.
It’s ARP (Address Resolution Protocol)
performing this translation between the IP world and Ethernet based on the
physical network. ARP enables machines to resolve addresses without using
static table that lists all addresses of both worlds. A machine uses ARP to
determine the recipient’s physical address by broadcasting an ARP request to
the subnet containing the IP address to be translated. The machine with the
relevant IP address responds with its physical address. To make ARP more
efficient, each machine maintains in memory a table of
addresses resolved and thus reduces the number of Broadcast emissions.
RARP (Reverse ARP) allows a machine to use its physical address to
determine its logical address on the Internet. The RARP mechanism
allows a computer to be identified as a target on the network
by broadcasting a RARP request. The servers receiving the message examine their
table and meet. Once the IP address obtained, the machine stores it in memory and
no longer uses RARP until it is reset.
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