Computer Networking Question(s)

[vincin]

Im in a computer networking class and need some explanations of things if anyone knows alot about networking. Okay, in the OSI model, I get the 7 layers....and each layer has certain functions right? well why do some layers repeat those tasks...like flow control, encryption. do packets turn into frames..that turn into bits???
whats packet sniffing? is there frame sniffing? bit sniffing??? SPDU sniffing!?!?

Why are the first 3 layers apart of the 'subnet' and not the other layers.

Whats the freaking purpose of the session and presentation layer?! they suck.

Wheres the "medium access layer" in the OSI model? data-link?? and whats the big deal about medium access...its boring.

Whats the point of token ring? it seems slow and pointless.

I just need a detailed explanation of this stuff from a computer expert. I understand programming, but networking seems like another system.