A network access server (NAS) is a group of components that provides remote users with a point of access to a network.

Overview

A NAS concentrates dial-in and dial-out user communications. An access server may have a mixture of analog and digital interfaces and support hundreds of simultaneous users. A NAS consists of a communications processor that connects asynchronous devices to a LAN or WAN through network and terminal emulation software. It performs both synchronous and asynchronous routing of supported protocols. The NAS is meant to act as a gateway to guard access to a protected resource. This can be anything from a

telephone A telephone, colloquially referred to as a phone, is a telecommunications device that enables two or more users to conduct a conversation when they are too far apart to be easily heard directly. A telephone converts sound, typically and most ...

network, to

printers Printer may refer to: Technology * Printer (publishing), a person * Printer (computing), a hardware device * Optical printer for motion picture films People * Nariman Printer (fl. c. 1940), Indian journalist and activist * James Printer (1 ...

, to the

Internet The Internet (or internet) is the Global network, global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a internetworking, network of networks ...

. A client connects to the NAS. The NAS then connects to another resource asking whether the client's supplied

credentials A credential is a piece of any document that details a qualification, competence, or authority issued to an individual by a third party with a relevant or '' de facto'' authority or assumed competence to do so. Examples of credentials include ac ...

are valid. Based on that answer the NAS then allows or disallows access to the protected resource.

Examples

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

Internet service provider An Internet service provider (ISP) is an organization that provides a myriad of services related to accessing, using, managing, or participating in the Internet. ISPs can be organized in various forms, such as commercial, community-owned, no ...

which provides network access via common modem or modem-like devices (be it

PSTN The public switched telephone network (PSTN) is the aggregate of the world's telephone networks that are operated by national, regional, or local telephony operators. It provides infrastructure and services for public telephony. The PSTN consists ...

DSL Digital subscriber line (DSL; originally digital subscriber loop) is a family of technologies that are used to transmit digital data over telephone lines. In telecommunications marketing, the term DSL is widely understood to mean asymmetric di ...

cable Cable may refer to: Mechanical * Nautical cable, an assembly of three or more ropes woven against the weave of the ropes, rendering it virtually waterproof * Wire rope, a type of rope that consists of several strands of metal wire laid into a hel ...

GPRS General Packet Radio Service (GPRS), also called 2.5G, is a mobile data standard on the 2G cellular communication network's Global System for Mobile Communications, global system for mobile communications (GSM). Networks and mobile devices wit ...

UMTS The Universal Mobile Telecommunications System (UMTS) is a 3G mobile cellular system for networks based on the GSM standard. UMTS uses Wideband Code Division Multiple Access, wideband code-division multiple access (W-CDMA) radio access technolog ...

) can have one or more NAS (network access server) devices which accept PPP,

PPPoE The Point-to-Point Protocol over Ethernet (PPPoE) is a network protocol for Encapsulation (networking), encapsulating Point-to-Point Protocol (PPP) frames inside Ethernet frames. It appeared in 1999, in the context of the boom of DSL as the solu ...

or PPTP connections, checking credentials and recording accounting data via back-end

RADIUS In classical geometry, a radius (: radii or radiuses) of a circle or sphere is any of the line segments from its Centre (geometry), center to its perimeter, and in more modern usage, it is also their length. The radius of a regular polygon is th ...

servers, and allowing users access through that connection. * The

captive portal A captive portal is a web page accessed with a web browser that is displayed to newly connected users of a Wi-Fi or wired network before they are granted broader access to network resources. Captive portals are commonly used to present a landing o ...

mechanism used by many

WiFi Wi-Fi () is a family of wireless network protocols based on the IEEE 802.11 family of standards, which are commonly used for Wireless LAN, local area networking of devices and Internet access, allowing nearby digital devices to exchange data by ...

providers: a user wants to access the Internet and opens a 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

protocol to connect to an AAA server and passes off the

username A user is a person who uses a computer or Computer network, network Service (systems architecture), service. A user often has a user account and is identified to the system by a username (or user name). Some software products provide serv ...

and

password A password, sometimes called a passcode, is secret data, typically a string of characters, usually used to confirm a user's identity. Traditionally, passwords were expected to be memorized, but the large number of password-protected services t ...

. 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

voice over IP Voice over Internet Protocol (VoIP), also known as IP telephony, is a set of technologies used primarily for voice communication sessions over Internet Protocol (IP) networks, such as the Internet. VoIP enables voice calls to be transmitted as ...

(VoIP). However, instead of using a username and password, many times a phone number or

IP Address An Internet Protocol address (IP address) is a numerical label such as that is assigned to a device connected to a computer network that uses the Internet Protocol for communication. IP addresses serve two main functions: network interface i ...

are used. If the phone number is a valid customer then the call can be completed. Other uses might be to verify whether a phone number has long distance access or a telephone card has minutes left.

Associated protocols

Although not required, NASs are almost exclusively used with authentication, authorization, and accounting (AAA) servers. Of the AAA protocols available,

tends to be the most widely used. The

Diameter In geometry, a diameter of a circle is any straight line segment that passes through the centre of the circle and whose endpoints lie on the circle. It can also be defined as the longest Chord (geometry), chord of the circle. Both definitions a ...

base protocol extends RADIUS services by providing error handling and inter-domain communications. This protocol is used in networks like the

IP Multimedia Subsystem The IP Multimedia Subsystem or IP Multimedia Core Network Subsystem (IMS) is a standardised architectural framework for delivering IP multimedia services. Historically, mobile phones have provided voice call services over a circuit-switched-sty ...

(IMS).

References

External links

* , Network Access Server Requirements Next Generation (NASREQNG) {{DEFAULTSORT:Network Access Server Network access Telephony Telecommunications infrastructure

Overview

Examples

Associated protocols

See also

References

External links