My usage doesn't = my ISP usage

With vista, I check my internet usage in the Network and Sharing Centre daily when shutting down, I shut down the satellite modem at the same time.
Yet when I check my usage at my ISP's website, they are constantly 10 or 20 or more mb a day over what my Network and sharing Centre has my usage as.
Anyone know Why?
I sometimes go over my usage limit because my ISP has me about 500mb per month over what I have added up daily from my Network and Sharing Centre.


Maybe some packet data between just the ISP and the modem. I think when you shut down and restart a modem that some data transfer takes place for authentication and so on. These days 10 to 20 mb is considered 'trivial' although I appreciate that on a restricted or metered connection every byte counts. It all sounds perfectly normal anyhow. Do you have to shut the modem down ?
No I don't have to shut down the modem, but I do.
What you said makes sense, I wonder if i didn't turn the modem off then there might not be that exchange between my ISP and my modem for authentication and so on, every day.
Thanks for that.


It was worth trying. Maybe it is just the ISP accessing the modem every so often (or the other way around) for verification of some sort.

I know I said earlier that it was a small amount, but actually when you multiply it out its not. Its over 0.8Gb in a 31 day month, and when I think that back in 2007 I was on a 2Gb allowance... so not so trivial after all.

Perhaps an email to your ISP might be worth pursuing, or seeing if there is a forum for your router manufacturer where you could ask specifically.