正确答案
试题解析
解析:Explanation:ARPfindsthehardwareaddressofahostfromaknownIPaddress.Here'showitworks:whenIPhasadatagramtosend,itmustinform.aNetworkAccessprotocol,suchasEthernetorTokenRing,ofthedestination'shardwareaddressonthelocalnetwork.(Ithasalreadybeeninformedbyupper-layerprotocolsofthedestination'sIPaddress.)IfIPdoesn'tfindthedestinationhost'shardwareaddressintheARPcache,itusesARPtofindthisinformation.ICMPworksattheNetworklayerandisusedbyIPformanydifferentservices.ICMPisamanagementprotocolandmessagingserviceproviderforIP.ItsmessagesarecarriedasIPdatagrams.RFC1256isanannextoICMP,whichaffordshosts'extendedcapabilityindiscoveringroutestogateways.Periodically,routeradvertisementsareannouncedoverthenetwork,reportingIPaddressesfortherouter'snetworkinterfaces.Hostslistenforthesenetworkinfomercialstoacquirerouteinformation.Aroutersolicitationisarequestforimmediateadvertisementsandmaybesentbyahostwhenitstartsup.