raviprakash sunkara wrote: Radius can be used as authentication mechanism. The user data (login + password) are stored in the Radius server and openser asks the Radius server for verification. Thus, verification of credentials is done inside the Radius server. The other alternative is to use a database backend (subscriber table) and openser authenicates against the credentials stored in the subscriber table. Thus, verification of credentials is done inside openser. use the auth_radius module (or the other radius modules if you need more features) No. Usually the Radius server is on another PC. If you do not know what Radius is and if you do not havfe the explicit requirement to use Radius, then do not use it and use auth_db instead (storing the user data in a database) Also take a look at this thread: http://mail.iptel.org/pipermail/serusers/2004-April/007407.html regards klaus