Bandwidth Monitoring-bytes sent/received

Does anyone know of an accurate monitoring tool that can tell me the number of bytes sent and received over the internet - preferably free? The Seven Network Status Window shows this for the current session but I'm not sure how accurate this is. Does any know?

I use Rainmeter with the Ioxx skin: http://albinozz.deviantart.com/art/Ioxx-Pack-131513476

It shows in bytes correctly. Of course, this only measures data from your computer and not the router.

Thanks. I'll have a look at that.