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<chapter id="advanced-networking">
  <title>Advanced Networking</title>
  
  <sect1 id="routing">
    <title>Gateways and Routes</title>
    
    <para><emphasis>Contributed by &a.gryphon;. 6 October
	1995.</emphasis></para>
	
    <para>For one machine to be able to find another, there must be a
      mechanism in place to describe how to get from one to the other. This is
      called Routing.  A &ldquo;route&rdquo; is a defined pair of addresses: a
      &ldquo;destination&rdquo; and a &ldquo;gateway&rdquo;.  The pair
      indicates that if you are trying to get to this
      <emphasis>destination</emphasis>, send along through this
      <emphasis>gateway</emphasis>.  There are three types of destinations:
      individual hosts, subnets, and &ldquo;default&rdquo;.  The
      &ldquo;default route&rdquo; is used if none of the other routes apply.
      We will talk a little bit more about default routes later on.  There are
      also three types of gateways: individual hosts, interfaces (also called
      &ldquo;links&rdquo;), and ethernet hardware addresses.</para>
	
    <sect2>
      <title>An example</title>
      
      <para>To illustrate different aspects of routing, we will use the
	following example which is the output of the command <command>netstat
	  -r</command>:</para>
	  
      <screen>Destination      Gateway            Flags     Refs     Use     Netif Expire

default          outside-gw         UGSc       37      418      ppp0
localhost        localhost          UH          0      181       lo0
test0            0:e0:b5:36:cf:4f   UHLW        5    63288       ed0     77
10.20.30.255     link#1             UHLW        1     2421 
foobar.com       link#1             UC          0        0 
host1            0:e0:a8:37:8:1e    UHLW        3     4601       lo0
host2            0:e0:a8:37:8:1e    UHLW        0        5       lo0 =>
host2.foobar.com link#1             UC          0        0
224              link#1             UC          0        0</screen>
	  
      <para>The first two lines specify the default route (which we will cover
	in the next section) and the <hostid>localhost</hostid> route.</para>
	  
      <para>The interface (<literal>Netif</literal> column) that it specifies
	to use for <literal>localhost</literal> is
	<devicename>lo0</devicename>, also known as the loopback device.  This
	says to keep all traffic for this destination internal, rather than
	sending it out over the LAN, since it will only end up back where it
	started anyway.</para>
      
      <para>The next thing that stands out are the <hostid
	  role="mac">0:e0:...</hostid> addresses.  These are ethernet hardware
	addresses.  FreeBSD will automatically identify any hosts
	(<hostid>test0</hostid> in the example) on the local ethernet and add
	a route for that host, directly to it over the ethernet interface,
	<devicename>ed0</devicename>.  There is also a timeout
	(<literal>Expire</literal> column) associated with this type of route,
	which is used if we fail to hear from the host in a specific amount of
	time.  In this case the route will be automatically deleted.  These
	hosts are identified using a mechanism known as RIP (Routing
	Information Protocol), which figures out routes to local hosts based
	upon a shortest path determination.</para>
	  
      <para>FreeBSD will also add subnet routes for the local subnet (<hostid
	  role="ipaddr">10.20.30.255</hostid> is the broadcast address for the
	subnet <hostid role="ipaddr">10.20.30</hostid>, and <hostid
	  role="domainname">foobar.com</hostid> is the domain name associated
	with that subnet).  The designation <literal>link#1</literal> refers
	to the first ethernet card in the machine.  You will notice no
	additional interface is specified for those.</para>
	  
      <para>Both of these groups (local network hosts and local subnets) have
	their routes automatically configured by a daemon called
	<command>routed</command>.  If this is not run, then only routes which
	are statically defined (ie. entered explicitly) will exist.</para>
	  
      <para>The <literal>host1</literal> line refers to our host, which it
	knows by ethernet address.  Since we are the sending host, FreeBSD
	knows to use the loopback interface (<devicename>lo0</devicename>)
	rather than sending it out over the ethernet interface.</para>
	  
      <para>The two <literal>host2</literal> lines are an example of what
	happens when we use an ifconfig alias (see the section of ethernet for
	reasons why we would do this).  The <literal>=&gt;</literal> symbol
	after the <devicename>lo0</devicename> interface says that not only
	are we using the loopback (since this is address also refers to the
	local host), but specifically it is an alias.  Such routes only show
	up on the host that supports the alias; all other hosts on the local
	network will simply have a <literal>link#1</literal> line for
	such.</para>
	  
      <para>The final line (destination subnet <literal>224</literal>) deals
	with MultiCasting, which will be covered in a another section.</para>
	  
      <para>The other column that we should talk about are the
	<literal>Flags</literal>.  Each route has different attributes that
	are described in the column.  Below is a short table of some of these
	flags and their meanings:</para>
	  
      <informaltable frame="none">
	<tgroup cols="2">
	  <tbody>
	    <row>
	      <entry>U</entry>
	      <entry>Up: The route is active.</entry>
	    </row>
	    
	    <row>
	      <entry>H</entry>
	      <entry>Host: The route destination is a single host.</entry>
	    </row>
	    
	    <row>
	      <entry>G</entry>
	      <entry>Gateway: Send anything for this destination on to this
		remote system, which will figure out from there where to send
		it.</entry>
	    </row>
	    
	    <row>
	      <entry>S</entry>
	      <entry>Static: This route was configured manually, not
		automatically generated by the system.</entry>
	    </row>
	      
	    <row>
	      <entry>C</entry>
	      <entry>Clone: Generates a new route based upon this route for
		machines we connect to. This type of route is normally used
		for local networks.</entry>
	    </row>
	    
	    <row>
	      <entry>W</entry>
	      <entry>WasCloned: Indicated a route that was auto-configured
		based upon a local area network (Clone) route.</entry>
	    </row>
	      
	    <row>
	      <entry>L</entry>
	      <entry>Link: Route involves references to ethernet
		hardware.</entry>
	    </row>
	  </tbody>
	</tgroup>
      </informaltable>
    </sect2>
    
    <sect2>
      <title>Default routes</title>
      
      <para>When the local system needs to make a connection to remote host,
	it checks the routing table to determine if a known path exists.  If
	the remote host falls into a subnet that we know how to reach (Cloned
	routes), then the system checks to see if it can connect along that
	interface.</para>
	  
      <para>If all known paths fail, the system has one last option: the
	&ldquo;default&rdquo; route.  This route is a special type of gateway
	route (usually the only one present in the system), and is always
	marked with a <literal>c</literal> in the flags field.  For hosts on a
	local area network, this gateway is set to whatever machine has a
	direct connection to the outside world (whether via PPP link, or your
	hardware device attached to a dedicated data line).</para>
      
      <para>If you are configuring the default route for a machine which
	itself is functioning as the gateway to the outside world, then the
	default route will be the gateway machine at your Internet Service
	Provider's (ISP) site.</para>
	  
      <para>Let us look at an example of default routes.  This is a common
	configuration:</para>
	    
      <literallayout>
[Local2]  &lt;--ether--&gt;  [Local1]  &lt;--PPP--&gt; [ISP-Serv]  &lt;--ether--&gt;  [T1-GW]
      </literallayout>
	  
      <para>The hosts <hostid>Local1</hostid> and <hostid>Local2</hostid> are
	at your site, with the formed being your PPP connection to your ISP's
	Terminal Server.  Your ISP has a local network at their site, which
	has, among other things, the server where you connect and a hardware
	device (T1-GW) attached to the ISP's Internet feed.</para>
      
      <para>The default routes for each of your machines will be:</para>
      
      <informaltable frame="none">
	<tgroup cols="3">
	  <thead>
	    <row>
	      <entry>host</entry>
	      <entry>default gateway</entry>
	      <entry>interface</entry>
	    </row>
	  </thead>
	  
	  <tbody>
	    <row>
	      <entry>Local2</entry>
	      <entry>Local1</entry>
	      <entry>ethernet</entry>
	    </row>
	    
	    <row>
	      <entry>Local1</entry>
	      <entry>T1-GW</entry>
	      <entry>PPP</entry>
	    </row>
	  </tbody>
	</tgroup>
      </informaltable>
      
      <para>A common question is &ldquo;Why (or how) would we set the T1-GW to
	be the default gateway for Local1, rather than the ISP server it is
	connected to?&rdquo;.</para>
	  
      <para>Remember, since the PPP interface is using an address on the ISP's
	local network for your side of the connection, routes for any other
	machines on the ISP's local network will be automatically generated.
	Hence, you will already know how to reach the T1-GW machine, so there
	is no need for the intermediate step of sending traffic to the ISP
	server.</para>
	  
      <para>As a final note, it is common to use the address <hostid
	  role="ipaddr">...1</hostid> as the gateway address for your local
	network.  So (using the same example), if your local class-C address
	space was <hostid role="ipaddr">10.20.30</hostid> and your ISP was
	using <hostid role="ipaddr">10.9.9</hostid> then the default routes
	would be:</para>
	  
      <literallayout>
Local2 (10.20.30.2)             --&gt;  Local1 (10.20.30.1)
Local1 (10.20.30.1, 10.9.9.30)  --&gt;  T1-GW (10.9.9.1)
      </literallayout>
    </sect2>
    
    <sect2>
      <title>Dual homed hosts</title>
      
      <para>There is one other type of configuration that we should cover, and
	that is a host that sits on two different networks. Technically, any
	machine functioning as a gateway (in the example above, using a PPP
	connection) counts as a dual-homed host.  But the term is really only
	used to refer to a machine that sits on two local-area
	networks.</para>
	  
      <para>In one case, the machine as two ethernet cards, each having an
	address on the separate subnets.  Alternately, the machine may only
	have one ethernet card, and be using ifconfig aliasing.  The former is
	used if two physically separate ethernet networks are in use, the
	latter if there is one physical network segment, but two logically
	separate subnets.</para>
	  
      <para>Either way, routing tables are set up so that each subnet knows
	that this machine is the defined gateway (inbound route) to the other
	subnet.  This configuration, with the machine acting as a Bridge
	between the two subnets, is often used when we need to implement
	packet filtering or firewall security in either or both
	directions.</para>
    </sect2>
    
    <sect2>
      <title>Routing propagation</title>
      
      <para>We have already talked about how we define our routes to the
	outside world, but not about how the outside world finds us.</para>
	  
      <para>We already know that routing tables can be set up so that all
	traffic for a particular address space (in our examples, a class-C
	subnet) can be sent to a particular host on that network, which will
	forward the packets inbound.</para>
	  
      <para>When you get an address space assigned to your site, your service
	provider will set up their routing tables so that all traffic for your
	subnet will be sent down your PPP link to your site.  But how do sites
	across the country know to send to your ISP?</para>
	  
      <para>There is a system (much like the distributed DNS information) that
	keeps track of all assigned address-spaces, and defines their point of
	connection to the Internet Backbone.  The &ldquo;Backbone&rdquo; are
	the main trunk lines that carry Internet traffic across the country,
	and around the world.  Each backbone machine has a copy of a master
	set of tables, which direct traffic for a particular network to a
	specific backbone carrier, and from there down the chain of service
	providers until it reaches your network.</para>
	  
      <para>It is the task of your service provider to advertise to the
	backbone sites that they are the point of connection (and thus the
	path inward) for your site.  This is known as route
	propagation.</para>
    </sect2>
    
    <sect2>
      <title>Troubleshooting</title>
      
      <para>Sometimes, there is a problem with routing propagation, and some
	sites are unable to connect to you.  Perhaps the most useful command
	for trying to figure out where a routing is breaking down is the
	  &man.traceroute.8; command.  It is equally useful if you cannot seem
	to make a connection to a remote machine (i.e. &man.ping.8;
	fails).</para>
	  
      <para>The &man.traceroute.8; command is run with the name of the remote
	host you are trying to connect to.  It will show the gateway hosts
	along the path of the attempt, eventually either reaching the target
	host, or terminating because of a lack of connection.</para>
	  
      <para>For more information, see the manual page for
	  &man.traceroute.8;.</para>
    </sect2>
  </sect1>
  
  <sect1 id="nfs">
    <title>NFS</title>
    
    <para><emphasis>Contributed by &a.jlind;.</emphasis></para>
    
    <para>Certain Ethernet adapters for ISA PC systems have limitations which
      can lead to serious network problems, particularly with NFS. This
      difficulty is not specific to FreeBSD, but FreeBSD systems are affected
      by it.</para>
	
    <para>The problem nearly always occurs when (FreeBSD) PC systems are
      networked with high-performance workstations, such as those made by
      Silicon Graphics, Inc., and Sun Microsystems, Inc.  The NFS mount will
      work fine, and some operations may succeed, but suddenly the server will
      seem to become unresponsive to the client, even though requests to and
      from other systems continue to be processed.  This happens to the client
      system, whether the client is the FreeBSD system or the workstation.  On
      many systems, there is no way to shut down the client gracefully once
      this problem has manifested itself. The only solution is often to reset
      the client, because the NFS situation cannot be resolved.</para>
	
    <para>Though the &ldquo;correct&rdquo; solution is to get a higher
      performance and capacity Ethernet adapter for the FreeBSD system, there
      is a simple workaround that will allow satisfactory operation.  If the
      FreeBSD system is the <emphasis>server</emphasis>, include the option
      <option>-w=1024</option> on the mount from the client.  If the FreeBSD
      system is the <emphasis>client</emphasis>, then mount the NFS file
      system with the option <option>-r=1024</option>.  These options may be
      specified using the fourth field of the <filename>fstab</filename> entry
      on the client for automatic mounts, or by using the <option>-o</option>
      parameter of the mount command for manual mounts.</para>
	
    <para>It should be noted that there is a different problem, sometimes
      mistaken for this one, when the NFS servers and clients are on different
      networks.  If that is the case, make <emphasis>certain</emphasis> that
      your routers are routing the necessary UDP information, or you will not
      get anywhere, no matter what else you are doing.</para>
	
    <para>In the following examples, <hostid>fastws</hostid> is the host
      (interface) name of a high-performance workstation, and
      <hostid>freebox</hostid> is the host (interface) name of a FreeBSD
      system with a lower-performance Ethernet adapter.  Also,
      <filename>/sharedfs</filename> will be the exported NFS filesystem (see
      <command>man exports</command>), and <filename>/project</filename> will
      be the mount point on the client for the exported file system.  In all
      cases, note that additional options, such as <option>hard</option> or
      <option>soft</option> and <option>bg</option> may be desirable in your
      application.</para>
	
    <para>Examples for the FreeBSD system (<hostid>freebox</hostid>) as the
      client: in <filename>/etc/fstab</filename> on freebox:</para>

    <programlisting>
fastws:/sharedfs /project nfs rw,-r=1024 0 0</programlisting>

    <para>As a manual mount command on <hostid>freebox</hostid>:</para>
	  
    <screen>&prompt.root; <userinput>mount -t nfs -o -r=1024 fastws:/sharedfs /project</userinput></screen>
	  
    <para>Examples for the FreeBSD system as the server: in
      <filename>/etc/fstab</filename> on <hostid>fastws</hostid>:</para>

    <programlisting>
freebox:/sharedfs /project nfs rw,-w=1024 0 0</programlisting>

    <para>As a manual mount command on <hostid>fastws</hostid>:</para>

    <screen>&prompt.root; <userinput>mount -t nfs -o -w=1024 freebox:/sharedfs /project</userinput></screen>
	  
    <para>Nearly any 16-bit Ethernet adapter will allow operation without the
      above restrictions on the read or write size.</para>
	
    <para>For anyone who cares, here is what happens when the failure occurs,
      which also explains why it is unrecoverable.  NFS typically works with a
      &ldquo;block&rdquo; size of 8k (though it may do fragments of smaller
      sizes).  Since the maximum Ethernet packet is around 1500 bytes, the NFS
      &ldquo;block&rdquo; gets split into multiple Ethernet packets, even
      though it is still a single unit to the upper-level code, and must be
      received, assembled, and <emphasis>acknowledged</emphasis> as a unit.
      The high-performance workstations can pump out the packets which
      comprise the NFS unit one right after the other, just as close together
      as the standard allows.  On the smaller, lower capacity cards, the later
      packets overrun the earlier packets of the same unit before they can be
      transferred to the host and the unit as a whole cannot be reconstructed
      or acknowledged.  As a result, the workstation will time out and try
      again, but it will try again with the entire 8K unit, and the process
      will be repeated, ad infinitum.</para>
    
    <para>By keeping the unit size below the Ethernet packet size limitation,
      we ensure that any complete Ethernet packet received can be acknowledged
      individually, avoiding the deadlock situation.</para>
	
    <para>Overruns may still occur when a high-performance workstations is
      slamming data out to a PC system, but with the better cards, such
      overruns are not guaranteed on NFS &ldquo;units&rdquo;.  When an overrun
      occurs, the units affected will be retransmitted, and there will be a
      fair chance that they will be received, assembled, and
      acknowledged.</para>
  </sect1>
  
  <sect1 id="diskless">
    <title>Diskless Operation</title>
    
    <para><emphasis>Contributed by &a.martin;.</emphasis></para>
    
    <para><filename>netboot.com</filename>/<filename>netboot.rom</filename>
      allow you to boot your FreeBSD machine over the network and run FreeBSD
      without having a disk on your client.  Under 2.0 it is now possible to
      have local swap.  Swapping over NFS is also still supported.</para>
	
    <para>Supported Ethernet cards include: Western Digital/SMC 8003, 8013,
      8216 and compatibles; NE1000/NE2000 and compatibles (requires
      recompile)</para>
    
    <sect2>
      <title>Setup Instructions</title>
      
      <procedure>
	<step>
	  <para>Find a machine that will be your server.  This machine will
	    require enough disk space to hold the FreeBSD 2.0 binaries and
	    have bootp, tftp and NFS services available. Tested
	    machines:</para>
	      
	  <itemizedlist>
	    <listitem>
	      <para>HP9000/8xx running HP-UX 9.04 or later (pre 9.04 doesn't
		work)</para>
	    </listitem>
	    
	    <listitem>
	      <para>Sun/Solaris 2.3.  (you may need to get bootp)</para>
	    </listitem>
	  </itemizedlist>
	</step>
	
	<step>
	  <para>Set up a bootp server to provide the client with IP, gateway,
	    netmask.</para>
	  
	  <programlisting>
diskless:\
        :ht=ether:\
        :ha=0000c01f848a:\
        :sm=255.255.255.0:\
        :hn:\
        :ds=192.1.2.3:\
        :ip=192.1.2.4:\
        :gw=192.1.2.5:\
        :vm=rfc1048:</programlisting>
	</step>
	
	<step>
	  <para>Set up a TFTP server (on same machine as bootp server) to
	    provide booting information to client.  The name of this file is
	    <filename>cfg.<replaceable>X.X.X.X</replaceable></filename> (or
	    <filename>/tftpboot/cfg.<replaceable>X.X.X.X</replaceable></filename>,
	    it will try both) where <replaceable>X.X.X.X</replaceable> is the
	    IP address of the client.  The contents of this file can be any
	    valid netboot commands.  Under 2.0, netboot has the following
	    commands:</para>

	  <informaltable frame="none">
	    <tgroup cols="2">
	      <tbody>
		<row>
		  <entry>help</entry>
		  <entry>print help list</entry>
		</row>
		
		<row>
		  <entry>ip
		    <option><replaceable>X.X.X.X</replaceable></option></entry>
		  <entry>print/set client's IP address</entry>
		</row>
		
		<row>
		  <entry>server
		    <option><replaceable>X.X.X.X</replaceable></option></entry>
		  <entry>print/set bootp/tftp server address</entry>
		</row>
		
		<row>
		  <entry>netmask
		    <option><replaceable>X.X.X.X</replaceable></option></entry>
		  <entry>print/set netmask</entry>
		</row>

		<row>
		  <entry>hostname <replaceable>name</replaceable></entry>
		  <entry>print/set hostname</entry>
		    </row>
		
		<row>
		  <entry>kernel
		    <option><replaceable>name</replaceable></option></entry>
		  <entry>print/set kernel name</entry>
		</row>
		
		<row>
		  <entry>rootfs
		    <option><replaceable>ip:/fs</replaceable></option></entry>
		  <entry>print/set root filesystem</entry>
		</row>
		
		<row>
		  <entry>swapfs
		    <option><replaceable>ip:/fs</replaceable></option></entry>
		  <entry>print/set swap filesystem</entry>
		</row>
		
		<row>
		  <entry>swapsize
		    <option><replaceable>size</replaceable></option></entry>
		  <entry>set diskless swapsize in Kbytes</entry>
		</row>
		
		<row>
		  <entry>diskboot</entry>
		  <entry>boot from disk</entry>
		</row>
		
		<row>
		  <entry>autoboot</entry>
		  <entry>continue boot process</entry>
		</row>
		
		<row>
		  <entry>trans
		    <option>on</option>|<option>off</option></entry>
		  <entry>turn transceiver on|off</entry>
		</row>
		
		<row>
		  <entry>flags
		    <option>b</option><option>c</option><option>d</option><option>h</option><option>s</option><option>v</option></entry>
		  <entry>set boot flags</entry>
		</row>
	      </tbody>
	    </tgroup>
	  </informaltable>
	  
	  <para>A typical completely diskless cfg file might contain:</para>

	  <programlisting>
rootfs 192.1.2.3:/rootfs/myclient
swapfs 192.1.2.3:/swapfs
swapsize 20000
hostname myclient.mydomain</programlisting>

	  <para>A cfg file for a machine with local swap might contain:</para>

	  <programlisting>
rootfs 192.1.2.3:/rootfs/myclient
hostname myclient.mydomain</programlisting>
	</step>
	
	<step>
	  <para>Ensure that your NFS server has exported the root (and swap if
	    applicable) filesystems to your client, and that the client has
	    root access to these filesystems A typical
	    <filename>/etc/exports</filename> file on FreeBSD might look
	    like:</para>
	  
	  <programlisting>
/rootfs/myclient -maproot=0:0 myclient.mydomain
/swapfs -maproot=0:0 myclient.mydomain</programlisting>

	  <para>And on HP-UX:</para>

	  <programlisting>
/rootfs/myclient -root=myclient.mydomain
/swapfs -root=myclient.mydomain</programlisting>
	</step>
	      
	<step>
	  <para>If you are swapping over NFS (completely diskless
	    configuration) create a swap file for your client using
	    <command>dd</command>.  If your <command>swapfs</command> command
	    has the arguments <filename>/swapfs</filename> and the size 20000
	    as in the example above, the swapfile for myclient will be called
	    <filename>/swapfs/swap.<replaceable>X.X.X.X</replaceable></filename>
	    where <replaceable>X.X.X.X</replaceable> is the client's IP addr,
	    eg:</para>
		  
	  <screen>&prompt.root; <userinput>dd if=/dev/zero of=/swapfs/swap.192.1.2.4 bs=1k count=20000</userinput></screen>
		  
	  <para>Also, the client's swap space might contain sensitive
	    information once swapping starts, so make sure to restrict read
	    and write access to this file to prevent unauthorized
	    access:</para>
		  
	  <screen>&prompt.root; <userinput>chmod 0600 /swapfs/swap.192.1.2.4</userinput></screen>
	</step>
	
	<step>
	  <para>Unpack the root filesystem in the directory the client will
	    use for its root filesystem (<filename>/rootfs/myclient</filename>
	    in the example above).</para>
	  
	  <itemizedlist>
	    <listitem>
	      <para>On HP-UX systems: The server should be running HP-UX 9.04
		or later for HP9000/800 series machines. Prior versions do not
		allow the creation of device files over NFS.</para>
	    </listitem>
	    
	    <listitem>
	      <para>When extracting <filename>/dev</filename> in
		<filename>/rootfs/myclient</filename>, beware that some
		systems (HPUX) will not create device files that FreeBSD is
		happy with.  You may have to go to single user mode on the
		first bootup (press control-c during the bootup phase), cd
		<filename>/dev</filename> and do a <command>sh ./MAKEDEV
		  all</command> from the client to fix this.</para>
	    </listitem>
	  </itemizedlist>
	</step>
	
	<step>
	  <para>Run <command>netboot.com</command> on the client or make an
	    EPROM from the <filename>netboot.rom</filename> file</para>
	</step>
      </procedure>
    </sect2>
    
    <sect2>
      <title>Using Shared <filename>/</filename> and <filename>/usr</filename>
	filesystems</title>
	  
      <para>At present there isn't an officially sanctioned way of doing this,
	although I have been using a shared <filename>/usr</filename>
	filesystem and individual <filename>/</filename> filesystems for each
	client.  If anyone has any suggestions on how to do this cleanly,
	please let me and/or the &a.core; know.</para>
    </sect2>
    
    <sect2>
      <title>Compiling netboot for specific setups</title>
      
      <para>Netboot can be compiled to support NE1000/2000 cards by changing
	the configuration in
	<filename>/sys/i386/boot/netboot/Makefile</filename>.  See the
	comments at the top of this file.</para>
    </sect2>
  </sect1>
  
  <sect1 id="isdn">
    <title>ISDN</title>
    
    <para><emphasis>Last modified by &a.wlloyd;</emphasis>.</para>
    
    <para>A good resource for information on ISDN technology and hardware is
      <ulink url="http://alumni.caltech.edu/~dank/isdn/">Dan Kegel's ISDN
	Page</ulink>.</para>
	
    <para>A quick simple roadmap to ISDN follows:</para>
    
    <itemizedlist>
      <listitem>
	<para>If you live in Europe I suggest you investigate the ISDN card
	  section.</para>
      </listitem>
      
      <listitem>
	<para>If you are planning to use ISDN primarily to connect to the
	  Internet with an Internet Provider on a dialup non-dedicated basis,
	  I suggest you look into Terminal Adapters.  This will give you the
	  most flexibility, with the fewest problems, if you change
	  providers.</para>
      </listitem>
      
      <listitem>
	<para>If you are connecting two lans together, or connecting to the
	  Internet with a dedicated ISDN connection, I suggest you consider
	  the stand alone router/bridge option.</para>
      </listitem>
    </itemizedlist>
    
    <para>Cost is a significant factor in determining what solution you will
      choose.  The following options are listed from least expensive to most
      expensive.</para>
    
    <sect2>
      <title>ISDN Cards</title>
      
      <para><emphasis>Contributed by &a.hm;.</emphasis></para>
      
      <para>This section is really only relevant to ISDN users in countries
	where the DSS1/Q.931 ISDN standard is supported.</para>
  
      <para>Some growing number of PC ISDN cards are supported under FreeBSD
	2.2.x and up by the isdn4bsd driver package.  It is still under
	development but the reports show that it is successfully used all over
	Europe.</para>

      <para>The latest isdn4bsd version is available from  <ulink
	  url="ftp://isdn4bsd@ftp.consol.de/pub/">ftp://isdn4bsd@ftp.consol.de/pub/</ulink>,
	the main isdn4bsd ftp site (you have to log in as user
	<username>isdn4bsd</username> , give your mail address as the password
	and change to the <filename>pub</filename> directory.  Anonymous ftp
	as user <username>ftp</username> or <username>anonymous</username>
	will <emphasis>not</emphasis> give the desired result).</para>

      <para>Isdn4bsd allows you to connect to other ISDN routers using either
	IP over raw HDLC or by using synchronous PPP.  A telephone answering
	machine application is also available.</para>

      <para>Many ISDN PC cards are supported, mostly the ones with a Siemens
	ISDN chipset (ISAC/HSCX), support for other chipsets (from Motorola,
	Cologne Chip Designs) is currently under development.  For an
	up-to-date list of supported cards, please have a look at the <ulink
	  url="ftp://isdn4bsd@ftp.consol.de/pub/README">README</ulink>
	file.</para>

      <para>In case you are interested in adding support for a different ISDN
	protocol, a currently unsupported ISDN PC card or otherwise enhancing
	isdn4bsd, please get in touch with <email>hm@kts.org</email>.</para>
	
      <para>A majordomo maintained mailing list is available.  To join the
	list, send mail to <email>majordomo@FreeBSD.org</email> and
	specify:</para>
      
      <programlisting>
subscribe freebsd-isdn</programlisting>

      <para>in the body of your message.</para>
    </sect2>
    
    <sect2>
      <title>ISDN Terminal Adapters</title>
      
      <para>Terminal adapters(TA), are to ISDN what modems are to regular
	phone lines.</para>
      
      <para>Most TA's use the standard hayes modem AT command set, and can be
	used as a drop in replacement for a modem.</para>
	  
      <para>A TA will operate basically the same as a modem except connection
	and throughput speeds will be much faster than your old modem.  You
	will need to configure <link linkend="ppp">PPP</link> exactly the same
	as for a modem setup.  Make sure you set your serial speed as high as
	possible.</para>
	  
      <para>The main advantage of using a TA to connect to an Internet
	Provider is that you can do Dynamic PPP.  As IP address space becomes
	more and more scarce, most providers are not willing to provide you
	with a static IP anymore.  Most standalone routers are not able to
	accommodate dynamic IP allocation.</para>
      
      <para>TA's completely rely on the PPP daemon that you are running for
	their features and stability of connection.  This allows you to
	upgrade easily from using a modem to ISDN on a FreeBSD machine, if you
	already have PPP setup.  However, at the same time any problems you
	experienced with the PPP program and are going to persist.</para>
	  
      <para>If you want maximum stability, use the kernel <link
	  linkend="ppp">PPP</link> option, not the user-land <link
	  linkend="userppp">iijPPP</link>.</para>
	  
      <para>The following TA's are know to work with FreeBSD.</para>
	  
      <itemizedlist>
	<listitem>
	  <para>Motorola BitSurfer and Bitsurfer Pro</para>
	</listitem>
	
	<listitem>
	  <para>Adtran</para>
	</listitem>
      </itemizedlist>
      
      <para>Most other TA's will probably work as well, TA vendors try to make
	sure their product can accept most of the standard modem AT command
	set.</para>
	  
      <para>The real problem with external TA's is like modems you need a good
	serial card in your computer.</para>
	  
      <para>You should read the <link linkend="uart">serial ports</link>
	section in the handbook for a detailed understanding of serial
	devices, and the differences between asynchronous and synchronous
	serial ports.</para>
      
      <para>A TA running off a standard PC serial port (asynchronous) limits
	you to 115.2Kbs, even though you have a 128Kbs connection. To fully
	utilize the 128Kbs that ISDN is capable of, you must move the TA to a
	synchronous serial card.</para>
	  
      <para>Do not be fooled into buying an internal TA and thinking you have
	avoided the synchronous/asynchronous issue.  Internal TA's simply have
	a standard PC serial port chip built into them.  All this will do, is
	save you having to buy another serial cable, and find another empty
	electrical socket.</para>
	  
      <para>A synchronous card with a TA is at least as fast as a standalone
	router, and with a simple 386 FreeBSD box driving it, probably more
	flexible.</para>
	  
      <para>The choice of sync/TA vs standalone router is largely a religious
	issue.  There has been some discussion of this in the mailing lists.
	I suggest you search the <ulink
	  url="http://www.FreeBSD.org/search.html">archives</ulink> for the
	complete discussion.</para>
    </sect2>
    
    <sect2>
      <title>Standalone ISDN Bridges/Routers</title>
      
      <para>ISDN bridges or routers are not at all specific to FreeBSD or any
	other operating system.  For a more complete description of routing
	and bridging technology, please refer to a Networking reference
	book.</para>
	  
      <para>In the context of this page, I will use router and bridge
	interchangeably.</para>
	  
      <para>As the cost of low end ISDN routers/bridges comes down, it will
	likely become a more and more popular choice.  An ISDN router is a
	small box that plugs directly into your local Ethernet network(or
	card), and manages its own connection to the other bridge/router.  It
	has all the software to do PPP and other protocols built in.</para>
	  
      <para>A router will allow you much faster throughput that a standard TA,
	since it will be using a full synchronous ISDN connection.</para>
	  
      <para>The main problem with ISDN routers and bridges is that
	interoperability between manufacturers can still be a problem.  If you
	are planning to connect to an Internet provider, I recommend that you
	discuss your needs with them.</para>
	  
      <para>If you are planning to connect two lan segments together, ie: home
	lan to the office lan, this is the simplest lowest maintenance
	solution.  Since you are buying the equipment for both sides of the
	connection you can be assured that the link will work.</para>
	  
      <para>For example to connect a home computer or branch office network to
	a head office network the following setup could be used.</para>
	  
      <example>
	<title>Branch office or Home network</title>
	
	<para>Network is 10 Base T Ethernet.  Connect router to network cable
	  with AUI/10BT transceiver, if necessary.</para>

	<!-- This should be a graphic -->
	<programlisting>
---Sun workstation     
|
---FreeBSD box
|
---Windows 95 (Do not admit to owning it)
|
Standalone router
   |
ISDN BRI line</programlisting>

	<para>If your home/branch office is only one computer you can use a
	  twisted pair crossover cable to connect to the standalone router
	  directly.</para>
      </example>
      
      <example>
	<title>Head office or other lan</title>
	
	<para>Network is Twisted Pair Ethernet.</para>
	
	<!-- This should be a graphic -->
	<programlisting>
    -------Novell Server
    | H |
    |   ---Sun      
    |   |
    | U ---FreeBSD
    |   |
    |   ---Windows 95
    | B |
    |___---Standalone router
                |
        ISDN BRI line</programlisting>
      </example>
      
      <para>One large advantage of most routers/bridges is that they allow you
	to have 2 <emphasis>separate independent</emphasis> PPP connections to
	2 separate sites at the <emphasis>same</emphasis> time.  This is not
	supported on most TA's, except for specific(expensive) models that
	have two serial ports. Do not confuse this with channel bonding, MPP
	etc.</para>
	  
      <para>This can be very useful feature, for example if you have an
	dedicated internet ISDN connection at your office and would like to
	tap into it, but don't want to get another ISDN line at work. A router
	at the office location can manage a dedicated B channel connection
	(64Kbs) to the internet, as well as a use the other B channel for a
	separate data connection.  The second B channel can be used for
	dialin, dialout or dynamically bond(MPP etc.) with the first B channel
	for more bandwidth.</para>
	  
      <para>An Ethernet bridge will also allow you to transmit more than just
	IP traffic, you can also send IPX/SPX or whatever other protocols you
	use.</para>
    </sect2>
  </sect1>
</chapter>

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