远程认证拨号用户服务(Remote Authentication Dial In User Service,RADIUS)是在网络访问服务器(Network Access Server,NAS)和集中存放认证信息的Radius服务器之间传输认证、授权和配置信息的协议。其协议的标准定义在IETF的RFC2865和RFC2866文件中。对于中小型企业NAS应用来说,以Linux为平台建立RADIUS服务器是非常好的选择。使用共享软件完全可以建立简洁、高效的RADIUS服务器,而且无须任何软件上的花费。 Remote Authentication Dial In User Service (RADIUS) is a protocol that transfers authentication, authorization, and configuration information between a Network Access Server (NAS) and a Radius server that centrally stores authentication information. The standard for its protocols is defined in the IETF RFC2865 and RFC2866 files. For small and medium-sized NAS applications, the establishment of a RADIUS server using Linux as a platform is a very good choice. The use of shared software can establish a simple and efficient RADIUS server, and without any software costs.