What is a Network Access Server (NAS)?

A network access server (NAS) is a device that manages remote logins to set up a point-to-point protocol connection. These devices are also referred to as media access gateways or remote access servers by some.

Regardless of the name, these devices manage authentication and enable users to access necessary resources. They can be used between users and a phone system or between users and the internet.

How Does a NAS (Network Access Server) Work?

A NAS serves as a gateway for users to access a wide range of resources. Users must pass through the NAS and successfully complete any authentication tests to access the resources they need.

You’ve likely used a NAS without realizing it. Years ago, accessing the internet required waiting for your computer to go through a series of beeps and buzzes, a process managed by a NAS during dial-up connections. Surprisingly, 2.1 million people still use dial-up systems at home today.

Here’s how the dial-up process works:

1. Modem connection: The user starts the computer, connects the modem, and opens a communication line.
2. Modem to NAS: The modem sends the user’s password and username to the NAS.
3. Authentication: Once the NAS verifies the credentials, it opens a gateway to the internet, allowing access to another server.

The NAS plays a simple yet crucial role here. It verifies the user’s credentials and opens a gateway for the user to access another server. Without a NAS, this process wouldn’t be possible.

While you might not hear the same beeps and clicks when logging into the internet at work, the process is fundamentally the same. Your request passes through a NAS to verify and grant access.

Similarly, if you’ve ever used a network printer, you’ve interacted with a NAS. Your computer connects to the NAS, which verifies your authorization, and then you can start your print job.

NAS Examples

We’ve provided several examples of NAS deployments, but network access servers have a variety of functions, from direct internet connectivity to using internet-supported services for communication.

Common functions of network access servers include:

1. Internet Service Providers (ISPs): A primary function of a NAS is to act as a gateway to protected remote resources. Most NAS devices are servers that ISPs use to grant their customers internet access. ISPs that provide internet via modem-like devices, such as cable or DSL, use NAS devices to handle authentication through point-to-point protocol (PPP), point-to-point tunneling protocol (PPTP), or point-to-point protocol over ethernet (PPPoE) connections.
2. Communication Applications (VoIP): In this context, the NAS authenticates users using credentials like IP addresses or phone numbers instead of individual usernames and passwords. If the phone number belongs to a valid, active customer and has specific properties (e.g., available minutes or long-distance access), the NAS will complete the call. Additionally, a NAS can support network management and optimization tasks, including load balancing, network resource management, and user session management.
3. Virtual Private Network (VPN): VPNs provide remote users with access to a private network. In enterprise settings, VPNs allow employees to securely connect to the company’s network and access necessary resources from any location. This is especially beneficial for companies with flexible workplace policies or a mobile workforce. A typical VPN setup includes a network access server combined with client software. Within this structure, the NAS authenticates employees as they connect to the VPN via the internet. Robust security is essential for these systems, as approximately 69 percent of VPN users connect via mobile devices.
4. DSL access multiplexers (DSLAMs): DSLAMs serve as a type of NAS, providing an aggregation point for multiple DSL connections.
5. Wireless network access servers: In wireless networks, such as cellular networks and Wi-Fi hotspots, NAS devices manage the connection and authentication of wireless devices to the network.
6. Remote access servers (RAS): Businesses use dedicated servers to allow remote employees to securely dial into the company’s network, often utilizing VPN technology.
7. Cable modem termination systems (CMTS): In cable internet networks, CMTS devices act as NAS.
8. Authentication servers: While not NAS themselves, servers running RADIUS or TACACS+ protocols collaborate with NAS to authenticate and authorize users.

Most NAS systems operate with authentication, authorization, and accounting services using the RADIUS protocol. This protocol typically runs in the background, facilitating quick and efficient network access management.

FAQ’s

How does a NAS manage authentication?

A NAS uses credentials provided by the user, such as usernames and passwords or IP addresses and phone numbers, to verify their identity. Once authenticated, the NAS opens a gateway to the required resources, such as the internet or a private network.

What is the role of a NAS in a dial-up connection?

In a dial-up connection, the NAS manages the authentication process. The user’s computer connects to the modem, which then sends the username and password to the NAS. Once verified, the NAS opens a gateway to the internet, allowing the user to access online resources.

Can you give an example of how a NAS is used in modern networks?

In modern networks, a NAS is often used in corporate environments to manage VPN connections. Remote employees connect to the company’s network via the internet, and the NAS authenticates their credentials before granting access to internal resources. This process ensures secure communication and resource access.

How do NAS devices support communication applications like VoIP?

For VoIP applications, a NAS uses credentials such as IP addresses or phone numbers to authenticate users. If the credentials match those of a valid customer, the NAS allows the call to proceed. NAS devices also support network optimization tasks like load balancing and resource management.

What is the significance of the RADIUS protocol in NAS operations?

The RADIUS protocol is crucial for NAS operations as it handles authentication, authorization, and accounting services. This protocol ensures that users are properly authenticated, authorized for access, and that their usage is accurately accounted for, enabling efficient network access management.

How does a NAS function in wireless networks?

In wireless networks, such as cellular and Wi-Fi hotspots, NAS devices manage the connection and authentication of wireless devices. They ensure that only authorized devices can access the network, maintaining security and proper resource allocation.

Are NAS devices still relevant in today’s internet infrastructure?

Yes, NAS devices are still relevant and widely used in today’s internet infrastructure. They play a crucial role in managing and securing connections across various types of networks, from traditional dial-up to modern broadband and wireless networks.

Conclusion

Network access servers (NAS) are crucial for managing authentication and enabling secure access to various resources. They facilitate connections for ISPs, support VPNs for remote work, and authenticate users in communication applications. By ensuring only authorized users can access protected resources, NAS devices remain vital in today’s digital infrastructure.