Your prof is probably unschooled into the depth of protocols and protocol stacks. He is quite unaware that when he sends this or that across the net exactly what happens to make those nice little *standardized* packets that any system can read, but only the one it's addressed to gets (yes, I'm not counting sniffers here, this is basic stuff).

The reason for the model is to set a standard from which all protocols are based, so that computers everywhere can communicate - it's the very foundation of networking. Without it, we'd be blocked from communication by 'language barriers' between computers. (hence the International Standards Organization invented it).

Tell Prof to stick that in his pipe with whatever else he's been smoking.

/me looks up 2 posts and sees that this has already been stated in a much larger form and apols for repeating.