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Network access server

(also NAS)

Network access server definition

A network access server is a specialized server that acts as a gateway to a larger network.

See also: DSLAM, wireless network security, remote access server

How NAS works

  • User authentication. The NAS verifies the credentials of users trying to access the network.
  • Authorization. NAS determines the network resources and services that the user can access.
  • Accounting. NAS tracks user activities (i.e., connection duration, amount of transferred data).

Examples of a network access server

  • ISP dial-up access servers. A classic example of NAS: internet service providers use NAS to provide dial-up internet access to customers.
  • DSL access multiplexers (DSLAMs). DSLAMs function as a type of NAS — they provide an aggregation point for multiple DSL connections.
  • Wireless network access servers. In wireless networks (i.e., cellular networks, Wi-Fi hotspots), NAS devices manage the connection and authentication of wireless devices to the network.
  • VPN servers. VPN servers act as NAS for users connecting to a private network over the internet. They authenticate users and encrypt traffic, providing secure access to network resources.
  • Remote access servers (RAS). Businesses use dedicated servers to enable remote employees to dial into the company’s network securely, often using VPN technology.
  • Cable modem termination systems (CMTS). In cable internet networks, CMTS devices function as NAS.
  • Authentication servers. While not NAS themselves, servers running RADIUS or TACACS+ protocols work with NAS to authenticate and authorize users.