Textbooks love to open networking with the OSI model. Seven layers, two mnemonics, a stack of vocabulary before anyone has touched a cable. That is a clean map if you already know the building. It is a bad first week if you do not.
In ITN 101 we skip the layers early on purpose. Week one is nodes, links, and protocols, said in ordinary English. Weeks two and three are the stuff you can trip over: copper, fiber, radio, connectors, and the boxes in the rack. Only after students have held a patch cable and watched a switch learn a MAC address do we put floor numbers on those boxes. A hub is floor one. A switch is floor two. A router is floor three. Suddenly the map has somewhere to hang.
Basically, a model is useful when it names things you have already met. Before that, it is seven labels floating in air. The OSI model is still coming (Network+ tests it, and the industry speaks it). We just refuse to start there. Troubleshooting is the real payoff of layers: you check one floor at a time instead of guessing in a building with no numbers. That skill lands better once the cable, the frame, and the address are already in the room.
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