Xidian University 为什么分层 You want to have the physical layer as separate as possible from the layer of the kinds of protocols you use to get data across the links of the networks. You want that to be as separate as possible from the protocols you use to do routing,congestion control,and those things. You want that to be very separate from the things that go on in the computers that use the network for ultimate error recovery and things like that. Also you want to design the network in such a way that all of those things are done separately and don't have to change when one finds a better way of doing something in one of these other layers.为什么分层 Also you want to design the network in such a way that all of those things are done separately and don't have to change when one finds a better way of doing something in one of these other layers. You want to have the physical layer as separate as possible from the layer of the kinds of protocols you use to get data across the links of the networks. You want that to be as separate as possible from the protocols you use to do routing, congestion control, and those things. You want that to be very separate from the things that go on in the computers that use the network for ultimate error recovery and things like that