in the states you guys use a cable modem called surfboard made by motorola. i know you can induce lag if you hit the standby button on the front. not all modems have a standby button. i know the surfboard 4100 and 4200 have them. not sure if it will have the same effect as a lag switch.
You have to be host to use a standby button to lag other people. If you try to standby when your not host, your just disconnecting yourself from the host and that doesnt affect anyone else but yourself.