Remote Authentication Dial-In User Service Protocol: UDP Ports: 1812, 1813, 1645, 1646 Better known of the two AAA standards. 3 RADIUS devices: RADIUS Server Can support multiple NASs Supports PAP, CHAP, and MS-CHAP ( PPP ) Network Access Servers ( NAS ) Group of systems that connect to the network Microsoft: Internet Authentication Service (IAS) Linux: FreeRADIUS Resources # https://en.wikipedia.org/wiki/RADIUS