path: root/doc/kwifimanager/index.docbook

<?xml version="1.0" ?>
<!DOCTYPE book PUBLIC "-//KDE//DTD DocBook XML V4.2-Based Variant V1.1//EN" "dtd/kdex.dtd" [
  <!ENTITY kwifimanager "<application>KWiFiManager</application>">
  <!ENTITY LAN "<acronym>LAN</acronym>">
  <!ENTITY kappname "&kwifimanager;">
  <!ENTITY package "tdenetwork">
  <!ENTITY % English "INCLUDE"> <!-- change language only here -->
  <!ENTITY % addindex "IGNORE">
]>
<book lang="&language;">
  <bookinfo>
    <title>The &kwifimanager; Handbook</title>
    <authorgroup>
      <author>
        <firstname>Stefan</firstname>
        <surname>Winter</surname>
        <affiliation>
          <address>
            <email>[email protected]</email>
          </address>
        </affiliation>
      </author>
      <!-- TRANS:ROLES_OF_TRANSLATORS -->
    </authorgroup>
    <legalnotice>&FDLNotice;</legalnotice>
    <copyright>
      <year>2002-05</year>
      <holder>Stefan Winter</holder>
    </copyright>
    <date>2005--05-11</date>
    <releaseinfo>3.5.0</releaseinfo>
    <abstract>
      <para>The &kwifimanager; suite can be used to configure and monitor wireless &LAN;
        cards. It consists of a stand-alone application and a module for the &kde; Control
        Center.</para>
    </abstract>
    <keywordset>
      <keyword>KDE</keyword>
      <keyword>wireless</keyword>
      <keyword>Wi-Fi</keyword>
      <keyword>wlan</keyword>
      <keyword>WEP</keyword>
      <keyword>wlan-ng</keyword>
    </keywordset>
  </bookinfo>
  <chapter id="introduction">
    <title>Introduction</title>
    <para> The &kwifimanager; suite is a set of tools which allows you to manage your wireless
      &LAN; Network Interface card (PC-Card, PCI or miniPCI) under the K Desktop Environment. It
      provides information about your current connection and lets you set up up to ten independent
      configurations and use up to four configrations that are pre-configured by distribution-specific
      scripts. If you are in a place where none of your preconfigured networks is available,
      you can also dynamically switch to an available network with almost no configuration effort.
      &kwifimanager; supports every wireless &LAN; card that uses the wireless extensions
      interface. This includes virtually all wireless &LAN; cards that are operational at all
      under the &Linux; operating system.</para>
  </chapter>
  <chapter id="using">
    <title>Using the &kwifimanager; suite</title>
    <sect1 id="kwifimanager-application">
      <title>The &kwifimanager; application</title>
      <para> Purpose of the main &kwifimanager; application is to show the currently active
        network configuration and to display connection quality and access points.</para>
      <para>The main application is launched by either typing<userinput>kwifimanager</userinput> at
        the command prompt of a console window or via the K Menu, where it is located by default in
          the<guisubmenu>Applications</guisubmenu> group. If &kwifimanager; is already running
        but minimised to the system tray then it can be restored by clicking once on the <link
          linkend="systrayicon">system tray icon</link>. If there is more than one wireless &LAN;
          card in your system, just open more than one instance of &kwifimanager;: every instance
          will show information about a different card automatically.
          The &GUI; elements of the application
        are explained in the following subsections.</para>
      <sect2 id="kwifimanager-main">
        <title>Main window</title>
        <para> The &kwifimanager; main window consists of five parts:</para>
        <sect3 id="signalquality">
          <title>Signal quality display</title>
          <para> Here you can see the quality and type of the active connection. The uppermost icon
            displays the general state of the wireless network via a set of pictograms:<itemizedlist>
              <listitem>
                <para> a wireless &LAN; card with a question tag means that no card was detected
                  or its state could not be determined</para>
              </listitem>
              <listitem>
                <para> a single laptop means that a wireless &LAN; card is inserted and in
                  Infrastructure mode, but there is no radio signal from access-points. The card is
                  out of range and can not communicate to the infrastructure network.</para>
              </listitem>
              <listitem>
                <para> a laptop that is connected to an access point means that a connection to an
                  access point is established.</para>
              </listitem>
              <listitem>
                <para> two laptops mean that your system is in Ad-Hoc mode without access points. It
                  may or may not have established a Peer-to-Peer connection.</para>
              </listitem>
            </itemizedlist>
          </para>
          <para> Below these pictograms is a small quality meter. It displays, in a cellular-like
            manner, the quality level of the current connection. This information is only available
            in Infrastructure mode. In Ad-Hoc mode, the level is always 0.</para>
          <para> This graphical information is supplemented by an integer value below the icon. It
            shows the signal quality, and is computed in one of two ways: <itemizedlist>
              <listitem>
                <para>a directly reported value from the card if the card supports
                  <quote>Quality</quote> reporting</para>
              </listitem>
              <listitem>
                <para>
                  <literal>(signal strength in dBm) - (noise level in dBm)</literal> for cards that
                  do not support that.</para>
              </listitem>
            </itemizedlist> You can manually change the method used by turning
            <guimenu>File</guimenu>, <guimenuitem>Use alternate strength calculation</guimenuitem>
            on or off. Turning the option on means to use the second method. If your card is out of
            range, the value is 0; if no card is inserted or your card is in Ad-Hoc mode it will
            show N/A.</para>
        </sect3>
        <sect3 id="speed">
          <title>Connection speed</title>
          <para> An indicator for the current connection speed is shown at the right-hand side of
            the main window above the configuration info. If the speed settings are set to AUTO, the
            value will change once in a while as the card adjusts the connection speed according to
            the signal quality. The scale of the bar graph will automatically adjust to up to 108
            MBit/s when the current connection speed exceeds 11 MBit/s.</para>
        </sect3>
        <sect3 id="current-config">
          <title>Current configuration</title>
          <para>Here you can find information about your card configuration. It displays the
            following information:</para>
          <itemizedlist>
            <listitem>
              <para> the network with which the card is connected to / tries to connect to
                  (<guilabel>Searching for network:</guilabel> or <guilabel>Connected to
                network:</guilabel>)</para>
            </listitem>
            <listitem>
              <para> the <acronym>MAC</acronym> address of the access point to which the card is
                connected.</para>
              <para> If the card is in Infrastructure mode but out of range, an appropriate warning
                  (<computeroutput>- no access point -</computeroutput>) is displayed to indicate
                that no connection is established.</para>
              <para> In Ad-Hoc mode, the field shows an address that is associated with one of the
                cards in the Ad-Hoc network. It displays a MAC address that has a non-global scope:
                its second bit is set to 1, which often results in a prefix of <quote>02:</quote>
                instead of <quote>00:</quote>. Many people think this is an error, but in fact it is
                done on purpose to show that the cell you are connected to is not an actual physical
                device, but rather an imaginary access point without a real physical address.</para>
              <informalexample>
                <para> Your card is the first card that enters Ad-Hoc mode with a given SSID. Then all other cards
                  entering Ad-Hoc mode with the same SSID will see your MAC-address, slightly modified: instead
                    of<computeroutput>00:xx:yy:zz:aa:bb</computeroutput> it will
                    show<computeroutput>02:xx:yy:zz:aa:bb</computeroutput>. This behavior is
                  intentional.</para>
              </informalexample>
            </listitem>
            <listitem>
              <para> on most cards (those that have the capability to report it), the frequency on
                which the card is transmitting data and the corresponding channel number is
                displayed.</para>
            </listitem>
            <listitem>
              <para> your local IP (version 4) address, if available. If no address could be
                retrieved from the networking subsystem, the word <guilabel>unavailable</guilabel>
                is displayed.</para>
            </listitem>
            <listitem>
              <para> encryption status (only if you have started &kwifimanager; as<systemitem
                  class="username">root</systemitem>). The display will only show
                <guilabel>off</guilabel> or <guilabel>active</guilabel>, but never the real key.
                This is intentional in order to not reveal the <acronym>WEP</acronym> key to people
                passing by the users screen.</para>
            </listitem>
          </itemizedlist>
        </sect3>
        <sect3 id="ap-info">
          <title>Access Point information (bottom area)</title>
          <para> The last line of the main window shows information about your AccessPoint. This
            requires that your system administrator provided a list of MAC addresses with a
            corresponding information. An example for such a list can be found
                in<filename>$<envar>KDEDIR</envar>/share/apps/kwifimanager/locations/DE_BW_Karlsruhe_University.loc</filename>
          </para>
          <para>If you want to set up a new list, simply create a file in the same format and copy
            it into the folder <filename class="directory"
              >$<envar>KDEDIR</envar>/share/apps/kwifimanager/locations/</filename>
          </para>
          <para>It will be automatically parsed at the next start of &kwifimanager;. If you have
            a list and want to have it included in future releases of &kwifimanager;, simply
            send it to the author or current maintainer.</para>
        </sect3>
        <sect3 id="scanning">
          <title>Information about available networks</title>
          <para> The lower-left area of the main window contains a button named <guibutton>Scan for
              networks...</guibutton>. If you click on this button, &kwifimanager; will attempt
            to retrieve a list of all networks that are in range of your card. The outcome of this
            scan depends on two factors: <itemizedlist>
              <listitem>
                <para>the overall ability of your card and driver to perform network scans</para>
              </listitem>
              <listitem>
                <para>if you have root permissions or not</para>
              </listitem>
            </itemizedlist> If your card or driver arent able to scan the network, your scanning
            results will always be empty. If you are not the root user, the list may be incomplete
            or outdated. </para>
          <para> In order to receive a reliable, current list of access points you will need to
            start the scan with root privileges, for example by using the &tdesu; utility to
            start &kwifimanager;</para>
          <para> If at least one network was found, you are presented with a table showing details
            of the network. It has four columns that inform you about <itemizedlist>
              <listitem>
                <para>the network name (or the string <guilabel>(hidden cell)</guilabel> if the name
                  is not disclosed by the access point during the scan)</para>
              </listitem>
              <listitem>
                <para>the type (whether is a <guilabel>Managed</guilabel> or an
                  <guilabel>Ad-Hoc</guilabel> network)</para>
              </listitem>
              <listitem>
                <para>the signal strength of the network</para>
              </listitem>
              <listitem>
                <para>and whether or not <acronym>WEP</acronym> encryption is used</para>
              </listitem>
            </itemizedlist> In case of an active <acronym>WEP</acronym> encryption, you can click on
            that column and enter the network key. &kwifimanager; will automatically try to
            guess if the key is a hexadecimal number or a string. </para>
          <para> If the network information for the highlighted network is complete (&ie; all
            columns contain meaningful information), you can use the button <guibutton>Switch to
              network</guibutton> to enter the selected network. If &kwifimanager; has no root
            privileges, you will be prompted with a password prompt to enter the root password in
            order to change the network. </para>
          <para> Clicking on <guibutton>Close</guibutton> dismisses the network information screen
            without changes to the existing settings. </para>
        </sect3>
      </sect2>
      <sect2 id="statistics">
        <title>Statistics Viewer</title>
        <para> Optionally, by selecting <guimenuitem>Connection statistics</guimenuitem> in the
            <guimenu>File</guimenu> menu, a separate window can be shown which displays the signal
          level and noise level graphs of the last 240 seconds. The signal level is displayed in
          blue and the noise level in red. The difference (SIGNAL minus NOISE) is the connection
          quality which is displayed in the main window.</para>
        <para>Some cards do not report meaningful noise information. If this is the case for your
          card and you get annoyed by the irrelevant red line, you can disable showing the noise
          level in the statistics window by unselecting <menuchoice>
            <guimenu> Config </guimenu>
            <guimenuitem> Show noise level in statistics </guimenuitem>
          </menuchoice> in the &kwifimanager; main window.</para>
      </sect2>
      <sect2 id="config-edit">
        <title>Configuration Editor</title>
        <para> By selecting<menuchoice>
            <guimenu>Config</guimenu>
            <guimenuitem>Configuration Editor</guimenuitem>
          </menuchoice> you are taken to the <link linkend="control-center">control center
          module</link> of &kwifimanager;. In case you are not the <systemitem class="username"
            >root</systemitem> user, a window will pop up requesting the <systemitem
            class="username">root</systemitem> password. This is because the configuration module
          allows you to change network connectivity und uses <userinput>ifconfig</userinput> to make
          changes, which requires root privileges.</para>
      </sect2>
      <sect2 id="misc">
        <title>Miscellaneous</title>
        <para>There are some minor additional features worth of being mentioned.</para>
        <sect3 id="acoustic-scanning">
          <title>Acoustic Scanning</title>
          <para>First, there is a feature named <guilabel>Acoustic Scanning</guilabel>. If this
            option is enabled, the connection quality is converted into an acoustic signal. A higher
            signal quality leads to a higher frequency of the <quote>beep</quote> output and to a
            more rapid beeping. If you've ever seen the Star Trek(tm) series you will see some
            parallels to their <quote>tricorders</quote>
          </para>
        </sect3>
        <sect3 id="logging">
          <title>Network logging</title>
          <para>A second feature is network logging. It just means that &kwifimanager; will log
            the name of the network you are connecting to every time your network changes. 
            This option is most useful when searching for the special network name
              <quote>any</quote>. In this mode, the card will log into any network it finds. The
            logfile's position is <filename class="directory"
            >$<envar>HOME</envar>/.kde/share/apps/kwifimanager/wireless-log</filename>
          </para>
        </sect3>
        <sect3>
          <title>Disabling the wireless network</title>
          <para>You can completely disable the card by selecting the option <guimenu>File</guimenu>
            <guimenuitem>Disable radio</guimenuitem>. Using this option will turn off the cards
            transmitter which effectively turns it off and saves a little bit of energy. This will
            only work for your card if it accepts changes to its
            <computeroutput>txpower</computeroutput> property.</para>
        </sect3>
      </sect2>
    </sect1>
    <sect1 id="systrayicon">
      <title>The system tray icon</title>
      <para>When &kwifimanager; is launched, it installs a small icon in the system tray. The icon contains
      parts of the information of the main window, namely the bar graph and optionally the signal strength
        number.  If you hover over the icon with the mouse for a few seconds, a tooltip will appear that 
        contains the currently connected network name. Whether or not the strength number shall be 
        shown can be configured via <guimenu>Config</guimenu>,
      <guimenuitem>Show Strength Number in System Tray</guimenuitem>.</para>
      <para>If you have configured &kwifimanager; to stay in the system tray when clicking on the 
        <guibutton>X</guibutton> button, the icon will stay in the tray persistently unless you really exit
      the application by clicking on <guimenu>File</guimenu>, <guimenuitem>Quit</guimenuitem>.</para>
      <para>You can always hide the main application to the system tray by clicking on the tray icon. Similarly,
      to restore the main application from the tray, just click on it once.</para>
    </sect1>
    <sect1 id="control-center">
      <title>The Control Center module</title>
      <para>The configuration module in the &kcontrolcenter; is perhaps the most useful part of
        the &kwifimanager; suite. Here you can actually change the basic settings of your
        wireless &LAN; card. The module can manage up to ten independent configurations for the
        card. If you dont need that many configurations, you can reduce the number of configs
        shown at any time by changing the <guilabel>Number of Configurations</guilabel> entry.
        If you have configured your wireless settings with a distribution-specific tool, chances are good
        that the &kcontrolcenter; module will automatically detect this and also read in and show that
        configuration. In any case these configurations will be read-only, because it is the distribution's
        job to handle updating these settings and the module should not interfere with their internal magic.
        Up to five additional preset configurations can be shown in addition to the ten
        that are self-definable. These configurations will have the name <guilabel>Vendor x</guilabel>
        to distinguish them from the others.
        The &kcontrolcenter; can even automatically set your card up whenever you start the module.
        Since establishing (or bringing down) a network connection is a security sensitive operation,
        any changes to the configuration can only be done by <systemitem class="username">root</systemitem>.</para>
      <sect2 id="configuration-tab">
        <title>The Configuration Tabs</title>
        <para>The configurations are split up in three parts: <itemizedlist>
          <listitem>
            <para>general configuration settings (like the network name)</para>
          </listitem>
          <listitem>
            <para>encryption settings</para>
          </listitem>
          <listitem>
            <para>power saving settings</para>
          </listitem>
          </itemizedlist>
          These parts are explained in the following sections.
        </para>
        <sect3 id="config_general">
          <title>General settings</title>
        <para>The upper part of the control center module consists of one to ten tabs labelled
            <guilabel>Config 1</guilabel> through <guilabel>Config 10</guilabel>. Each of these tabs
          can hold a configuration for your WLAN card. In addition (as explained above) up to five vendor-specific
          configurations may be visible, labelled <guilabel>Vendor 1</guilabel> through <guilabel>Vendor 5</guilabel>.</para>
        <para>The most important settings are always visible, the cryptography and power management
          options are only shown when activated. The perhaps most important element in each
          configuration tab is the field<guilabel>Network name</guilabel>. Here you can specify
          which network you would like to log into. You can either specify the name of your network
          directly, or you can try a scan on all available networks by setting the network name to
            <userinput>any</userinput>.</para>
        <para>In addition to the network name, you have to specify the type of network to log into.
          That's the purpose of the button group<guilabel>Operation mode</guilabel>. The
            option<guilabel>Managed</guilabel> means that the network consists of designated
          base stations, so-called <quote>access points</quote> or sometimes <quote>residential
          gateways</quote>. This is the most common operation mode for company networks. The second
            option,<guilabel>Ad-hoc</guilabel> means that your network is just a direct
          connection between computers, without access points. The three other options 
          (<guilabel>Repeater</guilabel>, <guilabel>Master</guilabel> and <guilabel>Secondary</guilabel>)
        are only very seldomly used. If you want to use them, please be aware that these settings are simply
        passed to the iwconfig program and have not been tested extensively. In case something doesnt
        work as expected, you are welcome to send a bug report.</para>
        <para>You can optionally set the connection speed for your connection. The setting
            <guilabel>auto</guilabel> should do for most uses, since the card will determine the
          appropriate speed itself. However, if you find that the speed changes every few seconds,
          for example when you have a weak connection, you can set the speed manually.</para>
        <para>Below these configuration items you will find a field named<guilabel>Execute script on
          connect:</guilabel>. Here you can enter the name of a script to execute after setting up
          the network connection. It will be
          executed whenever you hit the <guilabel>Activate configuration</guilabel> button and,
          optionally, automatically when you start the Control Center module. The script will have
          <systemitem class="username">root</systemitem> rights. This may lead to problems
          if you want to start an X application in the script and the X server belongs to someone
          else than root. You can make such scripts work correctly if you execute the X application
          via<userinput>
            <command>tdesu</command>
            <option>-u</option>
            <replaceable>USERNAME</replaceable>
            <option>-c</option>
            <replaceable>COMMAND</replaceable>
          </userinput>. Or, you can instruct your X server to also allow connections coming from
        root. You can do this with the <command>xhost</command> program.</para>
        </sect3>
        <sect3 id="config_crypto">
          <title>Cryptography settings</title>
        <para>The checkbox <guilabel>Use encryption</guilabel> determines whether or not encryption
          shall be activated. If it is checked, a button labelled <guibutton>Configure...</guibutton> becomes
          available which allows you to configure the details of encryption. 
          After pushing the button, you are presented the following settings in a new dialog: </para>
        <variablelist>
          <varlistentry>
            <term>
              <guilabel>Key to use:</guilabel>
            </term>
            <listitem>
              <para>You can define up to four secret keys for each configuration; in this field you
                can set which one you want to use to send encrypted packets. The card can always
              receive packets that are encrypted with <emphasis>any</emphasis> of the keys.</para>
              <tip><para>You can achieve asymetrical encryption (different keys for sending and receiving)
                if you configure your access point to send packets with a different key than the card. Just make
              sure that the partner station has the required key in any one of its key slots.</para></tip>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term>
              <guilabel>Crypto mode:</guilabel>
            </term>
            <listitem>
              <para>When encryption is activated, there are two ways to deal with incoming
                non-encrypted packets: discard or allow. When you set your card for <guilabel>Open</guilabel>,
                the card will also listen to non-encrypted packets.
                  <guilabel>Restricted</guilabel> will only allow encrypted network packets,
                any other packets are discarded.</para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term>
              <guilabel>Crypto keys:</guilabel>
            </term>
            <listitem>
              <para>This box lets you specify the secret keys to use for cryptography. To protect 
                your passwords, only asterisks will be shown when you enter a password. The &kcontrolcenter;
              module will automatically try to guess whether you want to set an encryption string
              or a hexadecimal number by checking the input length: string keys are usually 5 or 13
              characters long (for 64- or 128-Bit key lengths) whereas hex values are 10 or 26 characters
                long (please do not put a <quote>0x</quote> in front of hex keys).</para>
            </listitem>
          </varlistentry>
        </variablelist>
        <para>Be aware that the built-in cryptography support (named WEP for Wired Equivalent
          Privacy) is not very safe at all. See <xref linkend="wep"/> for details.</para>
        </sect3>
        <sect3 id="config_power">
          <title>Power saving settings</title>
        <para>The last configuration element that remains to be described is the power management.
          When checking the box <guilabel>Enable Power Management</guilabel> a button for the
          configuration of the setting will become active. After clicking this button, a new dialog will open
          and you will be presented
          some options that can help you save energy. The first two input fields named
            <guilabel>Sleep timeout</guilabel> and <guilabel>Wakeup period</guilabel>
          describe the periodicity of network online times for your wireless &LAN; card. The card will
          turn the radio antenna off for the time period (in seconds) specified in
            <guilabel>Sleep timeout</guilabel>. Afterwards it will be active for <guilabel>Wakeup
              period</guilabel> and will in that time establish the network connection and send/receive
          packets that queued up during the sleep time. If no network
          connection is found, it will go to sleep again immediately and the cycle begins again. The box named
            <guilabel>Receive packets</guilabel> below lets you specify which packets the card
          should listen to when awaken. You can either select <guilabel>Unicast only</guilabel>
          (which will only let your card listen to packets sent specifically to your card),
            <guilabel>Multi/Broadcast only</guilabel> (will only listen to packets sent to multiple
          machines and discard packets directed to your card) or <guilabel>Both</guilabel>. Most
          people should select the default value <guilabel>Both</guilabel>.</para>
        </sect3>
      </sect2>
      <sect2 id="auto-configuration">
        <title>Auto-configuration on &kcontrolcenter; Module startup</title>
        <para> If you wish, you can make &kwifimanager; initialize your wireless &LAN; card
          whenever you start the &kcontrolcenter; module. To do so, check the box <guilabel>Load
            preset configuration on startup</guilabel> and select the configuration you want to use
          in the listbox below. If you want to set the card to
          these settings at once, push the button <guilabel>Activate
        configuration</guilabel>.</para>
      </sect2>
      <sect2 id="autodetect">
        <title>Autodetecting your device</title>
        <para>&kwifimanager; needs to know the interface name of your wireless &LAN; card to
          apply any settings. You can either enter the information (&eg;
          <userinput>eth1</userinput> or<userinput>wlan0</userinput>) manually in the input field
          on the right-hand side of<guilabel>Settings apply to interface:</guilabel>, or let &kwifimanager;
          auto-detect the interface. To do so, push the button<guibutton>Autodetect
          interface</guibutton>. This will perform a scan on all interfaces listed in <filename
            class="directory">/proc/net/dev</filename> to find your card. The result of the scan
          will show up in the input field beside the button. If the field remains empty, no card was
          found. Please note that &kwifimanager; uses the wireless extensions to detect cards.
          If you use a card controlled by the wlan-ng package, &kwifimanager; only shows correct
          results if your driver has a compatibility layer for the wireless extensions
        built-in. In the case that there are multiple wireless LAN cards present on the system,
        scanning stops after the first card found. So, if you want to apply the settings to a different
        card than the one that was detected during the scan, you need to enter its interface name
        by hand.</para>
      </sect2>
    </sect1>
  </chapter>
  <chapter id="credits">
    <title>License and contributors</title>
    <para>Documentation copyright &copy; Stefan
        Winter<email>[email protected]</email>.</para> &underFDL; &underGPL;
    <!-- TRANS:CREDIT_FOR_TRANSLATORS -->
  </chapter>
  <appendix id="further-information">
    <title>Further Information</title>
    <para>This appendix contains some extra information of items concerning wireless &LAN; that
      are not directly related to &kwifimanager;.</para>
    <sect1 id="macaddress">
      <title>Notes on the MAC address display in Ad-hoc mode</title>
      <para>At first glance, the MAC address in the field <guilabel>Access Point</guilabel> seems to
        be wrong in Ad-hoc mode because it changes the first two digits of the MAC address
          to<computeroutput>02</computeroutput>. But actually, this is a hardcoded feature in
        wireless &LAN; cards.</para>
      <para>Usually a card is connected to a <quote>real</quote> access point. Then the correct MAC
        address is shown. If you change to Ad-hoc (or <quote>Peer-to-peer</quote>) mode, one of the
        computers must act as a server for the other computers. The first computer that enters a
        network will set itself as server. So, all other computers connecting to the same Ad-hoc
        network will see that first computer as network server. But since this computer is not a
          <quote>real</quote> server (that is, it is not a permanently available access point),
        clients should be aware that the network they are connecting to is not a permanent one. IEEE
        standards for MAC addresses have a place reserved for such (rare) occasions: MAC addresses that are
        not globally valid have a bit set to one that shows that these addresses are 
        <quote>locally administered</quote>. This bit is the second bit in transmit order, and the seventh
      bit in logical order and will hence raise the number of the MAC's first digit block from 00 to 02.</para>
      <para>You can compare this sort of address to the non-global IP addresses like<quote>192.168.*.*.</quote>
      </para>
      <para>So, the implementors of wireless networking agreed to give these<quote>virtual</quote>
        network servers a MAC address that is within the <quote>locally administered</quote> scope.
        To keep this virtual MAC address unique, they used a little trick: they only changed the
        first segment of the MAC address of the wireless &LAN; card, and since the remaining
        segments are still unique in the world, they have a unique address to use as network
        server.</para>
    </sect1>
    <sect1 id="wep">
      <title>Security considerations on <acronym>WEP</acronym> cryptography</title>
      <para>
        <acronym>WEP</acronym> cryptography is not very secure at all. A paper from
        cryptography analysts called the encryption algorithm <quote>kindergarten
        cryptography</quote>. Actually, software exists that exploits a huge security hole in the
        encryption standard. This software listens to the encrypted network traffic, analyzes it,
        and after only a few hours it reveals the password to enter the network in clear text. The
        more traffic on the network, the easier it is to find out the password because some packets are
        particularly weak because they carry a bad so-called initialisation vector (IV). Recent access
      points try to avoid these bad IVs, so it is getting harder to exploit the hole.</para>
      <para>If you are truly concerned about your security, do<emphasis>not</emphasis> use plain
          <acronym>WEP</acronym>. If you are just setting up a two-computer home network, well, then
        I guess<acronym>WEP</acronym> should do.</para>
      <para>There are many alternatives to <acronym>WEP</acronym> encryption. Its successors WPA and
        WPA2 are better designed and do a better job protecting your traffic, for example by dynamically changing
        the keys after a while.
        If you dont want to rely on the basic safety of the network link you could use
          <acronym>SSH</acronym> to communicate over the network. <acronym>SSH</acronym> is a
        program suite that encrypts data with its own algorithm, which is very secure. Another
        option is to use <acronym>PPTP</acronym>, the Point-to-Point-Tunneling protocol. However,
        even <acronym>PPTP</acronym> seems to be a bit leaky concerning encryption security. And
        finally, you could set up an IPSec tunnel (VPN connection) for your encrypted connections. As of yet, this
        encryption seems to be very safe and flexible.</para>
    </sect1>
  </appendix>
  <appendix id="compile">
    <title>Compilation and Installation</title> &install.intro.documentation;
    &install.compile.documentation;</appendix> &documentation.index;</book>