yasamoka wrotenuclearcat wroteYou should count on your ADSL modem
Alternatively, is it possible that he can use software that monitors data from a specific IP address, in this case the data coming from the IP address of the modem?
MAC address probably, it will be more precise, but i dont know about software for that. And if modem are on UPS, it will be good idea (if modem support that) to use SNMP, to query model. This way you can keep precise statistics across reboots.