Networkscanbeinterconnectedbydifferentdevicesinthephysicallayernetworkscanbeconnectedby()_orhubs.whichjustmovethebitsfromonenetworktoanidenticalnetwork.Onelayerupwefindbridgesandswitcheswhichoperateatdatalinklayer.Theycanaccept(请作答此空)examinetheMACaddressandforwardtheframestoadifferentnetworkwhiledoingminorprotocoltranslationintheprocessinmenetworklayer,wehaveroutersthatcanconnecttwonetworks,Iftwonetworkshave()networklayer,theroutermaybeabletotranslatebetweenthepackerformats.Inthetransportlayerwefindtransportgateway,whichcaninterfacebetweentwotransportconnectionsFinally,intheapplicationlayer,applicationgatewaystranslatemessage().Asanexample,gatewaysbetweenInternete-mailandX.400e-mailmust()thee-mailmessageandchangevariousheaderfields.
A.frimes
B.packets
C.packages
D.cells
正确答案是A