public RadiusAuthenticationProtocol getRadiusAuthProtocol()
            throws GuacamoleException {
        return environment.getRequiredProperty(
            RadiusGuacamoleProperties.RADIUS_AUTH_PROTOCOL
        );
    }
Returns the authentication protocol Guacamole should use when
communicating with the RADIUS server, as configured in
guacamole.properties.  This must match the configuration
of the RADIUS server, so that the RADIUS server and Guacamole
client are "speaking the same language."

@return
    The authentication protocol of the RADIUS server, 
    from guacamole.properties.

@throws GuacamoleException
    If guacamole.properties cannot be parsed.
extensions/guacamole-auth-radius/src/main/java/org/apache/guacamole/auth/radius/conf/ConfigurationService.java