Access servers (RADIUS clients)
An access server is a device that provides some level of access to a larger network. An access server using a RADIUS infrastructure is also a RADIUS client, sending connection requests and accounting messages to a RADIUS server. Examples of access servers are:

• Network access servers (NASs) that provide remote access connectivity to an organization network or the Internet. An example is a Windows 2000 computer running the Routing and Remote Access service and providing either traditional dial-up or virtual private network (VPN) remote access services to an organization's intranet.
• Wireless access points that provide physical layer access to an organization's network, using wireless-based transmission and reception technologies.
• Switches that provide physical layer access to an organization's network, using traditional LAN technologies such as Ethernet.

traditional...