edit- oh u want by network client.. well like it seems usually in these matters, if you had a linux connection server I'm sure theres a geek somewhere who wrote software to do what u need.. but setting it up could be time consuming. not sure of windows based solutions
or of course an expensive router that can generate these statistics, I'm sure cisco makes plenty that would suit the needs. but I'm sure thats not the route you'd go unless its a good sized business funded network