Address Resolution Protocol (ARP)

From Computing and Software Wiki

Testing

Address Resolution Protocol is a low level protocol on the physical layer of the network with the purpose of finding other hosts physical (hardware) addresses with their Internet Protocol (IP) addresses. ARP allows programs to work only with IP addresses by filling a cache with IP to physical addresses. The cache will generally have a timeout of about 20 minutes to clear out the IP to physical address bindings and will refill it with the same ones if needed which can allow for updating new physical addresses for certain IP addresses because of new hardware. ARP fills the cache with IP to physical address bindings by sending out broadcast messages of an ARP request type with a target hosts IP address asking for its physical address and at the same time giving its own IP to physical address binding. The receiver will decide whether or not its own IP address matches and if so will send a reply back to the original sender with its own IP to physical address. The original sender will decide to wait for a reply to continue processing or not, save the IP to physical binding of the requested host and can then use the physical address to directly send internet packets.

References

http://www.ietf.org/rfc/rfc826.txt
http://en.wikipedia.org/wiki/Address_Resolution_Protocol