Monitoring Local Network Traffic

Hi Everyone.

To start, I am not a network specialist so please dumb down your answers for my simple brain.

I have about 20 devices active in my LAN, from cel phones (android), laptops (windows and iPads), wired and wireless devices that connect to my BELL Connection Hub DSL router.

I am looking for a program that can monitor the traffic on my router and indicate which IP / MAC address on the network is using up the most of the bandwidth.

Any tools out there that can do this without having to install it on each device?