I've got a Xfinity > motorola arris surfboard SB6141 > M9 Plus. 

Since connection I have exceeded 1024GB bandwidth limit for 2 months running. 

Next month I am going to get charged ($200 per month!).

So I need to understand bandwidth usage by device to identoify and manage the bandwidth sucks. 

Xfinity won't give me an bandwidth information beyond total usage per month (not even daily which would be handy since not everyon that lives in my house is here every day). On my last call they told me that they only collected monthly data but could not explain how they do that without aggregating daily data for months that have different numbers of days. I know for a fact that they pull all the MAC addresses and use that data to link mulitple devices to single user profiles for advertising purposes so it's frustrating that the customer that is generating that data is not privy to the information but that's probably something for another forum. 

TP Link have explained that I can get device connection stats only not bandwidth information. 

I dont even seem to be able to get total monthly data usage from Deco to compare with Xfinity.

It seems like TP Link should be able to add to the monthlhy report. So I am tempted to pay $50 per month and go unlimited until that happens - but does anyone know if there is a reason why not or if this is on a dev list somewhere?

Or I need to put some hardware between my modem and Deco. Does anyone know a cheap and easy solution I am generally a mac house and could probably crank up an old unsed one if that didn't slow things down. 

Or I am looking at firewall devices like Firewalla but that seems like I am buying something that is highly duplicative to what I thought I was getting with Deco. 

Any thoughts or ideas on how I solves this as unchecked it's going to cost an extra $200 per month.