Disconnecting during ISP's Off-Peak

Greetings,

My ISP offers unlimited bandwidth during offpeak times (0200-1000). In order to take advantage you must disconnect and reconnect within this period.

Although I am a newbie, I do understand how to modify my Cron files, and where they're located.

So, therefore, my question is what is/are the best command(s) to use to disconnect my pppoe session and subsequently reconnect. Is there a graceful way to do this, so as to minimize my visitor's interruption? I'm currently running SME 5.6 Unsupported.

Thanks so much for your help.
-
Steve