work(请作答此空),systemsthateffectivelyisolateanorganization'sinternalnetworkstructurefroman()network,suchastheINTERNETisbecomingincreasinglypopular.Thesefirewallsystemstypicallyactasapplication-layer()betweennetworks,usuallyofferingcontrolledTELNET,FTP,andSMTPaccess.Withtheemergenceofmoresophisticated()layerprotocolsdesignedtofacilitateglobalinformationdiscovery,thereexistsaneedtoprovideageneral()fortheseprotocolstotransparentlyandsecurelytraverseafirewall.
A.safeguards B.firewalls C.routers D.switches正确答案B
