<sect1 id="connectivity-dialup-overview">

    <title>Overview</title>

    <para>
        This manual describes the configuration of two computers, one
        acting as server and other as client. The server computer (see
        <xref linkend="connectivity-dialup-server" />) will be
        configured to provide internet services and the client
        computer (see <xref linkend="connectivity-dialup-client" />)
        to make use of those internet services. The connection medium
        used by both client and server computer is the telelphone line
        (i.e., the same medium you use to realize telephone calls).
        In this configuration, both client and server computers use
        special devices named <quote>Modems</quote> to transmit data
        in form of sound across the telephone line (see <xref
        linkend="connectivity-dialup-modem" />).
    </para>
    
    <para>
        This infrastructure is made available to you free of charge,
        however, you should know that maintaining it might cost you
        both money and time. For example, for each hour the server
        computer is on production there is an electrical consume that
        need to be paid every month.  Likewise, each call that you
        establish from the client computer to the server computer will
        cost you money, based on the location you made the call from
        and the time you spend connected.
    </para>

    <para>
        To use this infrastructure, people connecting from the client
        computers to the server computer must agree the conditions
        described in <xref linkend="connectivity-dialup-policy" />.
    </para>

    <para>
        It is worth to mention that, you can configure one computer to
        act both as server and client. In this case, your computer
        acts as client of another server computer, not the one you
        have configured in the same computer of your client (i.e., you
        cannot call yourself and expect to answer any incoming call
        using the same line you used to make the outgoing call, it
        doesn't make any sense).  Likewise, your server will act as
        server for another client computer, not the one you have
        configured. In resume, you can both receive incoming calls or
        realize outgoing calls using the same telephone line, but only
        when the telephone line is free from any incoming or outgoing
        call.
    </para>

    <para>
        This infrastructure could result very useful to you when you
        want to share IP packages with your friends and the only
        communication medium you and your friends have access to is a
        telephone network.
    </para>

</sect1>