计算机网络自上而下第四版英文版答案1.Anetwork-layerpacketisadatagram.Arouterforwardsapacketbasedonthepacket’sIP(layer3)address.Alink-layerswitchforwardsapacketbasedonthepacket’sMAC(layer2)address.2.Datagram-basednetworklayer:forwarding;routing.AdditionalfunctionofVCbasednetworklayer:callsetup.3.Forwa