Blame Manuals/Tcpi-ug/Connectivity/Ppp/modem.docbook

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<sect1 id="connectivity-ppp-modem">
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    <title>The Modem Device</title>
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    <para>
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        In order to establish a PPP link between two computers using
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        the telephone line as medium for data transmission, you will
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        need to install and configure a modem device in each computer
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        you plan to connect. On the other hand, if you're planning to
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        use PPP to connect the same computer to different networks
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        simultaneously (e.g., to build a proxy between them), you will
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        need to install and configure one modem device for each
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        different network you plan to establish such simultaneous
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        connection in the same computer.
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    </para>
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    <sect2 id="connectivity-ppp-modem-install">
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    <title>Installing Modem Devices</title>
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    <para>
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        To install a modem device in the computer, you need to attach
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        the modem hardware to the computer and later the telephone
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        line to the modem hardware. To attach the modem hardware to
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        your computer, you need to connect the serial or USB cable
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        that comes from the modem hardware to the appropriate input on
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        your computer (whether serial or USB). To connect the modem
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        hardware to the telephone line, you need to unplug the cable
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        that connects your telephone device and plug it on the modem
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        device, specifically in the port reserved for data
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        transmission.  Later, using a similar cable, you could connect
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        your telephone device to the modem's telephone port, so you
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        can realize telephone calls when no data transmition take
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        place through modem's data port.
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    </para>
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    <para>
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        To be on the safe side, do everything related to hardware
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        installation with the computer turned off. Then, when
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        everthing has been put in place, turn the computer on. Once
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        the operating system is up and running, you can verify the
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        modem hardware using either the <command>lsusb</command> or
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        <command>lspci</command> commands, based on whether you
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        attached the modem device to an USB or serial port,
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        respectivly.  These commands need to be run with
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        administrative privileges, thus, you probably need to do
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        <command>sudo</command> on them or login as 
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        class="username">root</systemitem> user in order to execute
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        them. For example, assuming you logged in as 
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        class="username">root</systemitem> user and you installed an
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        USB modem hardware as mentioned before, the output of
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        <command>lsusb</command> command would be similar to that
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        following:
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    </para>
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<screen>
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Bus 003 Device 001: ID 0000:0000  
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Bus 001 Device 001: ID 0000:0000  
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Bus 001 Device 002: ID 058f:6366 Alcor Micro Corp. Multi Flash Reader
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Bus 002 Device 001: ID 0000:0000  
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Bus 005 Device 003: ID 06e0:f104 Multi-Tech Systems, Inc.
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MT5634ZBA-USB MultimodemUSB (new firmware)
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Bus 005 Device 001: ID 0000:0000  
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Bus 005 Device 002: ID 046d:c018 Logitech, Inc. Optical Wheel Mouse
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Bus 004 Device 001: ID 0000:0000 
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</screen>
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    <para>
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        The relevant line in this output is that one mentioning the
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        existence of your modem. For example, Multi-Tech System,
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        Inc.  MT5634ZBA-USB MultimodemUSB (new
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        firmware)<footnote>
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        <para>
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            I want to thank my friend Brians Suarez Alonso for
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            bringing this modem hardware to me and for his paitient,
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            resisting my repetitive calls at night to realize
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            connection tests.
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        </para>
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        </footnote>. This line confirms that your modem hardware is
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        supported by &TC;; and it is possible to transmit data through
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        it.  Otherwise, if the modem you installed doesn't appear in
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        this list, it is probably because such hardware is not
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        supported by &TC;;, yet.
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    </para>
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    <para>
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        Once you have confirmed the modem hardware has been installed
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        in the computer (either client or server), you need to
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        determine the device name the operating system assigned to it.
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        This information is required by programs like
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        <application>mgetty</application> and
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        <application>wvdial</application>, so they can know what
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        device to talk to.  Assuming you've connected your modem
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        device through an USB port, the operating system will assign
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        the the <filename>/dev/ttyACM0</filename> device file to talk
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        to it.  On the other hand, assuming you've connected your
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        modem device through a serial port, the operating system will
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        use the <filename>/dev/ttyS0</filename> device file to talk to
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        it.  To be absolutly sure about what device name the operating
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        system assigned to your modem hardware, you can use the
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        <command>lshal</command> command from <package>hal</package>
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        package.
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    </para>
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    </sect2>
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    <sect2 id="connectivity-ppp-modem-config">
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    <title>Configuring Modem Devices</title>
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    <para>
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        Inside &TC;;, modem devices can be configured using the
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        <command>system-config-network</command> tool. This tool is a
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        manages modem configuration files under the
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        <filename>/etc/sysconfig/network-scripts</filename> and
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        <filename>/etc/wvdial.conf</filename>.  Inside
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        <filename>/etc/sysconfig/network-scripts</filename>, modem
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        configuration files can take different file names. To identify
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        them you need to open the file and checking the value set on
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        <varname>DEVICE</varname> variable. This variable can take
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        values like ppp0 for the first modem device,
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        ppp1 for the second modem device, and so on for
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        other modem devices.
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    </para>
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    <para>
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        The configuration files of modem devices may vary based on
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        whether the computer is acting as server, client or both.
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        When you configure the modem device on the server computer,
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        you should take care of specifying both the IP address
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        (IPADDR) and the network mask (NETMASK) inside the
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        configuration file.  Otherwise, the established connection
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        might end up having the wrong IP information you need to
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        transfer data correctly through it, assuming the other end
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        isn't configured to specify it.  When you configure the modem
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        device on the server computer, there is no need for you to set
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        any configuration related to wvdial, unless you be thinking to
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        make your server computer to act as a client of another server
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        computer. In fact, in the server computer, you can create the
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        modem configuration file by yourself based on the information
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        provided at
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        <filename>/usr/share/doc/initscripts-*/sysconfig.txt
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        </filename>
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    </para>
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    <para>
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        When you configure the modem device on the client computer,
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        you don't need to take care of specifying either the IP
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        address or network mask because the server computer will
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        assign them for you. The assignment of client computer IP
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        address is configured by <application>ppp</application> daemon
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        when it is executed by <application>mgetty</application> after
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        an incoming call has arrived to modem's port.
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    </para>
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    <example id="connectivity-ppp-modem-config.fig-1">
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    <title>Modem configuration file</title>
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    <screenshot>
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    <screeninfo>Modem configuration file</screeninfo>
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    <mediaobject>
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    <textobject>
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<screen>
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# Please read /usr/share/doc/initscripts-*/sysconfig.txt
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# for the documentation of these parameters.
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TYPE=modem
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DEVICE=ppp0
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BOOTPROTO=none
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ONBOOT=no
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USERCTL=yes
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PEERDNS=yes
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AC=off
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BSDCOMP=off
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VJCCOMP=off
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CCP=off
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PC=off
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VJ=off
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LINESPEED=115200
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MODEMPORT=/dev/ttyACM0
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PROVIDER=ProviderName
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DEFROUTE=yes
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PERSIST=no
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PAPNAME=faith
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WVDIALSECT=ProviderName
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MODEMNAME=Modem0
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DEMAND=no
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IPV6INIT=no
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IDLETIMEOUT=600
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NETMASK=255.255.255.0
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IPADDR=192.168.1.1
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</screen>
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    </textobject>
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    </mediaobject>
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    </screenshot>
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    </example>
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    </sect2>
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</sect1>