Multiple Services - Single Login

Hi, I am curious to understand the best means of providing multiple service authentications, such as PPPoE, Dialup, VPN, etc, via one login and password. I have seen it done before by NAS-IP-Address but it would quite cumbersome in our network. I was fooling around with the "NAS-Port-Type" but am having mixed results. Is there a better way to determine the type of service? Thanks, -- Nick Huanca