How to deal with this ...

Hi Guys, Using Freeradius for authorization, accounting and ip pools management. By mistake i turned off my NAS, and when this NAS came back online then freeradius began rejecting my users as if they were still connected, should my NAS send some kind of "Accounting restart let's start again" packet to Freeradius in order to let him know that those users are no longer connected? am i right? if not how can i deal with this kind of problems? apart from not being so stupid again to turn off a nas by mistake .... Thanks in advance, Ezequiel.