Network Access Server - Examples

Examples

The above translates into different implementations for different uses. Here are some examples.

  • An Internet Service Provider which provides network access via common modem or modem-like devices (be it PSTN, DSL, cable or GPRS/UMTS) can have one or more NAS (network access server) devices which accept PPP, PPPoE or PPTP connections, checking credentials and recording accounting data via back-end RADIUS servers, and allowing users access through that connection.
  • A sample use is the captive portal mechanism used by many WiFi providers: a user wants to access the Internet. He opens his browser. The NAS detects that the user is not currently authorized to have access to the Internet, so the NAS prompts the user for their username and password. The user supplies them and sends them back to the NAS. The NAS then uses the RADIUS protocol to connect to an AAA server and passes off the username and password. The RADIUS server searches through its resources and finds that the credentials are valid and notifies the NAS that it should grant the access. The NAS then grants the user access to the internet.
  • Another use of a NAS would be in VoIP. However, instead of using a username and password, many times a phone number or IP Address are used. If the phone number is a valid customer then the call can be completed. Other uses might be if the phone number has long distance access or if a telephone card has minutes left.

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