An Access Server or Network Access Server(NAS) is a connection server that connects network components to a local area network( LAN) or wide area network(WAN) using emulation software. The Network Access Server is used to connectusers to the Internet Service Provider( ISP).
A Network Access Server interfaces with both the local network operator, such as the telecommunications company, and the Internet backbone. NAS servers are controlled by AAA servers, Authentication, Authorization, and Accounting (AAA). These authenticate users and their logins by verifying their names and passwords. After verification by the AAA server, the NAS server can provide the user with the network and service for which the AAA server has granted authorization. The NAS server thus provides the client with the communication link between the user and the service server.