Networks

I am new network and a system administrator in a company with almost 500 workers.
My problem is workers connect to the internet anytime at their work stations and I want to implement a system that will restrict internet usage at working hours but not all users will be restricted because some uses the internet for their work.

I want to be able to restrict usage, bandwidth control, mac filtering and a firewall that could prevent unauthorized users. I need your advise thank you.