RADIUS stands for Remote Authentication Dial In User Service. RADIUS is a generic authentication, authorization, and accounting protocol. It contains commands for identifying a user and authenticating that user via various methods. Significantly, RADIUS is extensible, which means that vendors can (and have) created proprietary extensions to the basic RADIUS protocol. These extensions are referred to as RADIUS "dialects." Naturally, it's important that a RADIUS client and server be able to talk using compatible dialects. 

RADIUS is used in 802.11 by WPA and 802.11i, among others. A wireless client wishing to join the network uses the EAP protocol to request authentication from the AP. The AP is configured with the IP address of a RADIUS server, and passes the authentication request to the server using the RADIUS protocol. The server determines whether the client is authorized (which may involve the exchange of more RADIUS and EAP frames--for example, a challenge/response of some sort), and then notifies the AP whether the authentication succeeded. The advantage of this architecture is two-fold: authentication is centralized at the RADIUS server, meaning that clients can authenticate to any AP that is configured to use their RADIUS server; and many organizations already have a RADIUS server--e.g. for dial-up or VPN authentication--which means that the wireless authentication can integrate smoothly into the existing security infrastructure. 

RFID

Radio Frequency Identification. RFID technology is an automatic way to collect product, place, time or transaction data quickly and easily without human intervention or error. An RFID system comprises a reader (or interrogator), its associated antenna and the transponders (Tags/ RFID Cards) that carry the data. In much the same way that UPC bar codes are scanned with hand-held and permanent laser scanners today (like at the grocery store checkout lane), RFID scanning provides product identification information to a central system. Instead of a UPC bar code, the RFID information is contained in a "tag" affixed to the product. The RFID reader transmits a low-power radio signal, through its antenna, that the tag receives via its own antenna to power an integrated circuit (chip). Using the energy it gets from the signal when it enters the radio field, the tag will briefly converse with the reader for verification and the exchange of data. Once that data is received by the reader it can be sent to a controlling computer for processing and management. Be sure to read our additional discussion of RFID technology in the Wi-Fi: Just the Facts section and additional technical material on the Connect802 RFID backhaul network design consulting page.