<sect1 id="server-usage-connections">

    <title>Administering Dial-Up Connections</title>

    <para>
        The lifetime of dial-up connections must be limitted based on
        the number of users you expect to establish connection and the
        kind of services you plan to provide. The mail service
        provided by the server computer is conceived as a public
        service so anyone with a modem attached to a computer would be
        able to have access to it.  However, due to hardware
        limitations, only 100 users will be allowed to be registered
        in the public mail service. Based on this information, the
        lifetime of established connections will be of 15 minutes from
        the established moment on. Once the connection has been
        established, if the link is idle for 1 minute, the server
        computer will close the established connection to free the
        telephone line.  This control can be implemented through the
        <option>maxconnect</option> and <option>idle</option> options
        inside the <application>pppd</application>'s configuration
        file.
    </para>

    <para>
        Only registered user profiles will be able to establish connections
        to the server computer.  This control can be implemented using
        the <option>allow-number</option> option in the
        <application>pppd</application>'s configuration file to define a
        list of all telephone numbers that are allowed to establish
        connection with the server computer, based on the list of
        registered user profiles.  By default, all telephone numbers
        are denied from establishing access with the server computer,
        except those ones explicitly set by
        <option>allow-number</option> option.  If the
        <option>allow-number</option> option is not present in
        <application>pppd</application>'s configuration file, all
        telephone numbers are allowed to establish connection with the
        server computer, so be sure to include the
        <option>allow-number</option> option in
        <application>pppd</application>'s configuration file if you
        want to control who can/cannot establish connection with the
        server computer.
    </para>

<screen>
##### centos-pppd-config will overwrite this part!!! (begin) #####
allow-number 12345
allow-number 21345
allow-number 34567
##### centos-pppd-config will overwrite this part!!! (end) #####
</screen>

    <para>
        The <application>centos-pppd-admin</application> application
        must be considered part of user profile registration process
        inside the server computer. The
        <application>centos-pppd-admin</application> application would
        be used to control the list of allowed telephone numbers
        inside the <application>pppd</application>'s configuration
        file, based on the list of user profiles. The
        <application>centos-pppd-admin</application> application
        should be executed after any registration/deletion action
        against the list of user profiles with <systemitem
        class="username">root</systemitem> privilages in order to be
        able of writing the settings on
        <application>pppd</application>'s configuration file.
    </para>

    <para>
        Redialing consecutive connections from the same telephone
        number without any dealy between call retries must be avoided
        from client computers. This would reduce the possibilities for
        other client computers to establish connection with the server
        computer. To prevent this issue from happening, it would be
        necessary to provide more telephone lines than users
        authorized to establish connection with the server computer.
        Nevertheless, there is only one telephone line available for
        the server computer to use.
    </para>
    
</sect1>