Allocate and Trace Internet Usage

I need some helps on how to allocate or monitor the internet usage of my home. I dont have a server, I just use a broadband Belkin router so everyone in the house can online. People are getting irresponsible in using monthly download usage. I’m wondering are there any tools that i could use to trace a usage of via IP or MAC or allocate usage for each of the users. My router does not have that function. Any helps would be appreciated.

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