【71-75】The Address Resolution Protocol（ARP）wasDeveloped to enableCommunication onAn InternetworkAndperformArequired function in IP routing.ARP liesBetween layers（71）of the OSI model,andAllowsComputerstointroduce each otherAcrossA network prior toCommunication.APR finds the（72）address ofA hostfromitsknown（73）address.BeforeADevice sendsADatagram toAnotherDevice,it looks in itsARPCache toseeifthereisA MACAddressAndCorresponding IPAddress for theDestinationDevice.If there is no entry,the soureeDevicesendsA（74）message to everyDevice on the network.EachDeviceCompares the IPAddress to itsown.OnlytheDevice with the matching IPAddress replies withA packetContaining the MACAddress for theDevice（exceptin theCase of “proxyARP”）.The sourceDeviceAdds the（75）device MACAddress to itsARP tableforfuturereference.
