Nortel (Northern Telecom) Nortel (Northern Telecom) This document describes an architecture and the protocol used with respect to a Network Access Server (NAS), when modems are outsourced from the data network operator to the carrier network operator. At the heart of modem outsourcing there are several key areas, namely, varied mechanisms for authentication, authorization based on network wide state and policy for resource sharing, accounting/auditing and other management functions.