How is bandwidth usage monitored?

The total amount of bandwidth to and from a particular computer is monitored on a daily basis and follows the machine's hardware address (MAC address). Note: A hardware address (also referred to as a "MAC" or "Media Access Control" address) consists of twelve hexadecimal values, sometimes in a continuous string, other times separated by dashes or colons (e.g., 00-00-0C-03-F3-55 or 00000C03F355). This address is unique to each network device on a computer--no two computers will have the same MAC address. Computers having more than one network card (e.g., one for wireless and one for wired) will also have one MAC address for each network card.  more