@ Canis Lupus: What I mean is that you could sink 20 years into learning every detail about every protocol out there and still not be anymore capable then you are now. So many things are specifically implemented in a way so that they are invisible to everything that isn't part of the same EDIT: or adjacent OSI layer. Even more categories of information are just going to be irrelevant to your goal; for example MDI is a crucial component of any network around the world and everyone who goes to college for this kind of stuff learns about it. But it is not very likely to help you crack into your friends laptop.