private synchronized static void cleanUpAllExpiredSession() {
		Iterator it = sessions.entrySet().iterator();
		long currTime = new Date().getTime();
		while(it.hasNext()) {
			Map.Entry pair = (Map.Entry)it.next();
			Session iSession = (Session)pair.getValue();
			if(iSession.isExpired(currTime)) {
				it.remove();
			}
			
		}
	}