</authorgroup>

      </authorgroup>

    </info>

    </info>

    <para>For one machine to be able to find another over a network,

    <para>For one machine to be able to find another over a network,

      there must be a mechanism in place to describe how to get from

      there must be a mechanism in place to describe how to get from

host2.example.com link#1             UC          0        0

host2.example.com link#1             UC          0        0

224              link#1             UC          0        0</screen>

224              link#1             UC          0        0</screen>

      <para>The first two lines specify the default route, described

      <para>The first two lines specify the default route, described

	in more detail in <xref linkend="network-routing-default"/>,

	in more detail in <xref linkend="network-routing-default"/>,

	and the <systemitem>localhost</systemitem> route.</para>

	and the <systemitem>localhost</systemitem> route.</para>

      <para>The interface (<literal>Netif</literal> column) that this

      <para>The interface (<literal>Netif</literal> column) that this

	routing table specifies to use for

	routing table specifies to use for

	<literal>localhost</literal> is <filename>lo0</filename>,

	<literal>localhost</literal> is <filename>lo0</filename>,

	<primary>Ethernet</primary>

	<primary>Ethernet</primary>

	<secondary>MAC address</secondary>

	<secondary>MAC address</secondary>

      </indexterm>

      </indexterm>

      <para>The addresses beginning with <systemitem

      <para>The addresses beginning with <systemitem

	  class="etheraddress">0:e0:</systemitem> are Ethernet

	  class="etheraddress">0:e0:</systemitem> are Ethernet

	hardware addresses, also known as <acronym>MAC</acronym>

	hardware addresses, also known as <acronym>MAC</acronym>

	calculates routes to local hosts based upon a shortest path

	calculates routes to local hosts based upon a shortest path

	determination.</para>

	determination.</para>

      <para>&os; will add subnet routes for the local subnet.

      <para>&os; will add subnet routes for the local subnet.

	<systemitem class="ipaddress">10.20.30.255</systemitem> is the

	<systemitem class="ipaddress">10.20.30.255</systemitem> is the

    <sect2 xml:id="network-routing-default">

    <sect2 xml:id="network-routing-default">

      <title>Default Routes</title>

      <title>Default Routes</title>

      <para>When the local system needs to make a connection to a

      <para>When the local system needs to make a connection to a

	remote host, it checks the routing table to determine if a

	remote host, it checks the routing table to determine if a

    <sect2 xml:id="network-dual-homed-hosts">

    <sect2 xml:id="network-dual-homed-hosts">

      <title>Dual Homed Hosts</title>

      <title>Dual Homed Hosts</title>

      <para>A dual-homed system is a host which resides on two

      <para>A dual-homed system is a host which resides on two

	different networks.</para>

	different networks.</para>

    <sect2 xml:id="network-dedicated-router">

    <sect2 xml:id="network-dedicated-router">

      <title>Building a Router</title>

      <title>Building a Router</title>

      <para>A network router is a system that forwards packets from

      <para>A network router is a system that forwards packets from

	one interface to another.  Internet standards and good

	one interface to another.  Internet standards and good

	<literal>1</literal>.  To stop routing, reset this to

	<literal>1</literal>.  To stop routing, reset this to

	<literal>0</literal>.</para>

	<literal>0</literal>.</para>

      <para>The new router will need routes to know where to send the

      <para>The new router will need routes to know where to send the

	traffic.  If the network is simple enough, static routes can

	traffic.  If the network is simple enough, static routes can

	be used.  &os; comes with the standard BSD routing daemon

	be used.  &os; comes with the standard BSD routing daemon

	<title>Setting Up Static Routes</title>

	<title>Setting Up Static Routes</title>

	<authorgroup>

	<authorgroup>

	</authorgroup>

	</authorgroup>

      </info>

      </info>

      <!-- Feb 2004 -->

      <!-- Feb 2004 -->

	<primary>kernel options</primary>

	<primary>kernel options</primary>

	<secondary>MROUTING</secondary>

	<secondary>MROUTING</secondary>

      </indexterm>

      </indexterm>

      <para>&os; natively supports both multicast applications and

      <para>&os; natively supports both multicast applications and

	multicast routing.  Multicast applications do not require any

	multicast routing.  Multicast applications do not require any

	special configuration of &os;; as applications will generally

	special configuration of &os;; as applications will generally

      <title>Wireless Networking</title>

      <title>Wireless Networking</title>

      <authorgroup>

      <authorgroup>

      </authorgroup>

      </authorgroup>

    </info>

    </info>

    <indexterm>

    <indexterm>

      <primary>802.11</primary>

      <primary>802.11</primary>

      <see>wireless networking</see>

      <see>wireless networking</see>

    </indexterm>

    </indexterm>

      <title>USB Tethering</title>

      <title>USB Tethering</title>

    </info>

    </info>

    <para>Many cellphones provide the option to share their data

    <para>Many cellphones provide the option to share their data

      connection over USB (often called "tethering").  This feature

      connection over USB (often called "tethering").  This feature

	    <surname>Lucistnik</surname>

	    <surname>Lucistnik</surname>

	  </personname>

	  </personname>

	  <contrib>Written by </contrib>

	  <contrib>Written by </contrib>

	</author>

	</author>

      </authorgroup>

      </authorgroup>

    </info>

    </info>

    <sect2>

    <sect2>

      <title>Introduction</title>

      <title>Introduction</title>

      <title>Host Controller Interface

      <title>Host Controller Interface

	(<acronym>HCI</acronym>)</title>

	(<acronym>HCI</acronym>)</title>

      <para>The Host Controller Interface (<acronym>HCI</acronym>)

      <para>The Host Controller Interface (<acronym>HCI</acronym>)

	provides a command interface to the baseband controller and

	provides a command interface to the baseband controller and

      <title>Logical Link Control and Adaptation Protocol

      <title>Logical Link Control and Adaptation Protocol

	(<acronym>L2CAP</acronym>)</title>

	(<acronym>L2CAP</acronym>)</title>

      <para>The Logical Link Control and Adaptation Protocol

      <para>The Logical Link Control and Adaptation Protocol

	(<acronym>L2CAP</acronym>) provides connection-oriented and

	(<acronym>L2CAP</acronym>) provides connection-oriented and

      <title>Service Discovery Protocol

      <title>Service Discovery Protocol

	(<acronym>SDP</acronym>)</title>

	(<acronym>SDP</acronym>)</title>

      <para>The Service Discovery Protocol (<acronym>SDP</acronym>)

      <para>The Service Discovery Protocol (<acronym>SDP</acronym>)

	provides the means for client applications to discover the

	provides the means for client applications to discover the

      <title><acronym>OBEX</acronym> Object Push

      <title><acronym>OBEX</acronym> Object Push

	(<acronym>OPUSH</acronym>) Profile</title>

	(<acronym>OPUSH</acronym>) Profile</title>

      <para><acronym>OBEX</acronym> is a widely used protocol for

      <para><acronym>OBEX</acronym> is a widely used protocol for

	simple file transfers between mobile devices.  Its main use

	simple file transfers between mobile devices.  Its main use

	is in infrared communication, where it is used for generic

	is in infrared communication, where it is used for generic

      <title>Bridging</title>

      <title>Bridging</title>

      <authorgroup>

      <authorgroup>

      </authorgroup>

      </authorgroup>

    </info>

    </info>

    <sect2>

    <sect2>

      <title>Introduction</title>

      <title>Introduction</title>

      <para>It is sometimes useful to divide one physical network,

      <para>It is sometimes useful to divide one physical network,

	such as an Ethernet segment, into two separate network

	such as an Ethernet segment, into two separate network

	segments without having to create <acronym>IP</acronym>

	segments without having to create <acronym>IP</acronym>

      <sect3>

      <sect3>

	<title>Filtering/Traffic Shaping Firewall</title>

	<title>Filtering/Traffic Shaping Firewall</title>

	<para>A common situation is where firewall functionality is

	<para>A common situation is where firewall functionality is

	  needed without routing or Network Address Translation

	  needed without routing or Network Address Translation

	  on the network.  In this situation, using a router-based

	  on the network.  In this situation, using a router-based

	  firewall is difficult because of subnetting issues.</para>

	  firewall is difficult because of subnetting issues.</para>

	<para>A bridge-based firewall can be configured and dropped

	<para>A bridge-based firewall can be configured and dropped

	  into the path just downstream of the <acronym>DSL</acronym>

	  into the path just downstream of the <acronym>DSL</acronym>

	  or <acronym>ISDN</acronym> router without any

	  or <acronym>ISDN</acronym> router without any

    <sect2>

    <sect2>

      <title>Firewalling</title>

      <title>Firewalling</title>

      <para>When packet filtering is enabled, bridged packets will

      <para>When packet filtering is enabled, bridged packets will

	pass through the filter inbound on the originating interface

	pass through the filter inbound on the originating interface

      <title>Link Aggregation and Failover</title>

      <title>Link Aggregation and Failover</title>

      <authorgroup>

      <authorgroup>

      </authorgroup>

      </authorgroup>

    </info>

    </info>

    <para>&os; provides the &man.lagg.4; interface which can be used

    <para>&os; provides the &man.lagg.4; interface which can be used

      to aggregate multiple network interfaces into one virtual

      to aggregate multiple network interfaces into one virtual

      <title>Diskless Operation</title>

      <title>Diskless Operation</title>

      <authorgroup>

      <authorgroup>

      </authorgroup>

      </authorgroup>

      <authorgroup>

      <authorgroup>

      </authorgroup>

      </authorgroup>

    </info>

    </info>

    <para>A &os; machine can boot over the network and operate

    <para>A &os; machine can boot over the network and operate

      without a local disk, using file systems mounted from an

      without a local disk, using file systems mounted from an

      <title>Network Address Translation</title>

      <title>Network Address Translation</title>

      <authorgroup>

      <authorgroup>

      </authorgroup>

      </authorgroup>

    </info>

    </info>

      <indexterm>

      <indexterm>

	<primary>&man.natd.8;</primary>

	<primary>&man.natd.8;</primary>

      </indexterm>

      </indexterm>

      <para>&os;'s Network Address Translation

      <para>&os;'s Network Address Translation

	(<acronym>NAT</acronym>) daemon, &man.natd.8;, accepts

	(<acronym>NAT</acronym>) daemon, &man.natd.8;, accepts

	incoming raw <acronym>IP</acronym> packets, changes the

	incoming raw <acronym>IP</acronym> packets, changes the

      <indexterm>

      <indexterm>

	<primary><acronym>NAT</acronym></primary>

	<primary><acronym>NAT</acronym></primary>

      </indexterm>

      </indexterm>

      <para>The most common use of <acronym>NAT</acronym> is to

      <para>The most common use of <acronym>NAT</acronym> is to

	perform what is commonly known as Internet Connection

	perform what is commonly known as Internet Connection

	Sharing.</para>

	Sharing.</para>

	<primary>kernel</primary>

	<primary>kernel</primary>

	<secondary>configuration</secondary>

	<secondary>configuration</secondary>

      </indexterm>

      </indexterm>

      <para>When modules are not an option or if it is preferable to

      <para>When modules are not an option or if it is preferable to

	build all the required features into a custom kernel, the

	build all the required features into a custom kernel, the

	following options must be in the custom kernel configuration

	following options must be in the custom kernel configuration

    <sect2 xml:id="network-natdaddress-redirection">

    <sect2 xml:id="network-natdaddress-redirection">

      <title>Address Redirection</title>

      <title>Address Redirection</title>

      <para>Address redirection is useful if more than one

      <para>Address redirection is useful if more than one

	<acronym>IP</acronym> address is available.  Each

	<acronym>IP</acronym> address is available.  Each

	<acronym>LAN</acronym> client can be assigned its own

	<acronym>LAN</acronym> client can be assigned its own

  <sect1 xml:id="network-atm">

  <sect1 xml:id="network-atm">

    <info><title>Asynchronous Transfer Mode (<acronym>ATM</acronym>)</title>

    <info><title>Asynchronous Transfer Mode (<acronym>ATM</acronym>)</title>

      <authorgroup>

      <authorgroup>

      </authorgroup>

      </authorgroup>

    </info>

    </info>

	  </personname>

	  </personname>

	  <contrib>Contributed by </contrib>

	  <contrib>Contributed by </contrib>

	</author>

	</author>

	<author>

	<author>

	  <personname>

	  <personname>

	    <firstname>Allan</firstname>

	    <firstname>Allan</firstname>