Definition
A network access server is a device or server that acts as a gateway between users and network resources, such as the Internet or internal systems.
How NAS Works
- Authentication: The NAS verifies the identity of users attempting to access the network.
- Authorization: The NAS specifies the network resources and services available to the user.
- Accounting: NAS monitors user activity, such as connection time and data usage.
Examples of a Network Access Server
- ISP dial-up access servers: NAS enables internet service providers (ISPs) to provide dial-up internet access.
- DSL access multiplexers (DSLAMs): DSLAMs act as NAS by providing an aggregation point for several DSL connections.
- VPN servers: VPN servers function as NAS by linking users to private networks online. They verify users and encrypt traffic, ensuring secure access to network resources.
- Wireless network access servers: Most wireless networks, such as Wi-Fi hotspots and cellular networks, use NAS to manage the authentication and connection of wireless devices.
- Cable modem termination systems (CMTS): CMTS devices act as NAS in cable internet networks.
- Remote access servers (RAS): RAS functions as NAS by providing remote users access to a network.
- Authentication servers: Although they aren’t NAS, servers executing TACAS+ or RADIUS protocols employ NAS to authorize and authenticate users.
Difference Between NAS and NAD
- Network Access Server (NAS): A NAS is a server or software that provides remote access to a network, acting as a gateway to enable users to connect and access network resources. It authenticates and authorizes users, facilitates data transfer, and manages connection sessions.
- Network Access Device (NAD): On the other hand, NAD is an umbrella term covering devices involved in network access control, such as routers, switches, firewalls, wireless access points, etc. They can handle functions related to network access, including policy enforcement, user authentication, and traffic routing.