why is the ip address divided into a network part and a host part? would not be simpler to process it as a single id that uniquely identifies a host? a. the network and host parts are needed for implementing hierarchical routing. this makes routing table sizes and router processing times manageable, as opposed to storing addresses for each possible destination host. this remains so even if the network part has variable size in cdir. b. it would be simpler to process the address as a single, unique id, but that would make multicast very hard. c. the division into network and host parts is needed to maintain organizational boundaries and subnetting.