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+ <meta name="Description" content="Software and systems for realtime digital communications between amateur radio stations for the provision of information on propagation conditions and stations operating">
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+ <h2>Hops, Network Isolation and other matters...</h2>
+ <hr>
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+
+
+ <address><a href="mailto:djk@tobit.co.uk">Dirk Koopman G1TLH</a></address>
+ <p>
+ <!-- Created: Sun Dec 13 20:25:14 GMT 1998 -->
+ <!-- hhmts start -->
+Last modified: Sun Dec 20 18:15:15 GMT 1998
+<!-- hhmts end -->
+
+ <h4>Introduction</h4>
+
+ Starting with version 1.13 there is simple hop control available on a per
+ node basis. Also it is possible to isolate a network completely so that you
+ get all the benefits of being on that network, but can't pass on information
+ from it to
+ to any other networks you may be connected to (or vice versa).
+
+ <h4>Basic Hop Control</h4>
+
+ The number of hops that are set for all PC protocol messages (that require them)
+ are specified in <tt>/spider/perl/DXProtVars.pm</tt>.
+
+ <p>In versions prior to 1.13 you would move this file to
+ <tt>/spider/local/</tt> and modify the perl variables:
+ <tt>$def_hopcount</tt> and <tt>%hopcount</tt> to some reasonable
+ values.
+
+ <p>From version 1.13 onwards a new mechanism has been introduced
+ which uses a file called <tt>/spider/data/hop_count.pl</tt>. The
+ prefered way of doing basic hop control is now to create this file
+ and modify it as you wish. Eventually this file will contain all
+ the hop control and related information. An example of the
+ <tt>hop_count.pl</tt> file can be found in the
+ <tt>/spider/examples</tt> directory.
+
+ <p>You can change this file at any time, including when the
+ cluster is running. If you do this then the changes only take
+ effect after you have run the <tt>load/hops</tt> command on a
+ client console with full sysop privileges.
+
+ <h4>Per Node Hop Control</h4>
+
+ From version 1.13 it is possible to control the number of hops to each
+ node. This is done by adding information to the <tt>%nodehops</tt> perl
+ variable in the <tt>hop_count.pl</tt> file (as described above). This
+ variable is a perl "hash of hashes", which means that you create an
+ entry for every callsign you wish to control and then one line for
+ every PC protocol message that you wish to alter.
+
+ <p>You can also have a entry called <tt>default</tt> for every callsign
+ so you can set the hops as a whole for all PC messages to just that
+ callsign. This is overridden by any specific hop counts you may have.
+
+ <h4>Example <tt>hop_count.pl</tt> File</h4>
+
+ An example for you:-
+
+ <p><pre>
+#
+# hop table construction
+#
+
+package DXProt;
+
+# default hopcount to use
+$def_hopcount = 15;
+
+# some variable hop counts based on message type
+%hopcount =
+(
+ 11 => 10,
+ 16 => 10,
+ 17 => 10,
+ 19 => 10,
+ 21 => 10,
+);
+
+#
+# the per node hop control thingy
+#
+
+%nodehops =
+(
+ GB7DJK-1 =>
+ {
+ 11 => 5,
+ 16 => 23,
+ 17 => 23,
+ default => 50,
+ },
+
+ GB7TLH =>
+ {
+ 19 => 45,
+ 21 => 45,
+ 16 => 45,
+ 17 => 45,
+ default => 15,
+ },
+);
+ </pre>
+
+ <p>The figures chosen are not necessarily what I use. What I would say is that
+ until you are certain that you know what you are doing (and that the software
+ is working at least as well as advertised) you should keep the default hop
+ counts down to the sort of levels shown above.
+
+ <h4>Isolated Networks</h4>
+
+ It is possible to isolate networks from each other on a "gateway" node using
+ the <tt>set/isolate <node call></tt> command.
+
+ <p>The effect of this is to partition an isolated network
+ completely from another nodes connected to your node. Your node
+ will appear on and otherwise behave normally on every network to
+ which you are connected, but data from isolated network will not
+ cross onto any other network or vice versa.
+
+ <P>However all the spot, announce and WWV traffic and personal
+ messages will still be handled locally (because you are a real
+ node on all connected networks), that is locally connected users
+ will appear on all networks and will be able to access and receive
+ information from all networks transparently.
+
+ <p>All routed messages will be sent as normal, so if a user on one
+ network knows that you are a gateway for another network, he can still
+ still send a talk/announce etc message via your node and it will
+ be routed across.
+
+ <p>The only limitation currently is that non-private messages
+ cannot be passed down isolated links regardless of whether they
+ are generated locally. This will change when the bulletin routing
+ facility is added.
+
+<!-- Standard Footer!! -->
+ <p> </p>
+ <p>
+ <FONT COLOR="#606060"><hr></font>
+ <font color="#FF0000" size=-2>
+ Copyright © 1998 by Dirk Koopman G1TLH. All Rights Reserved<br>
+ </font>
+ <font color="#000000" size=-2>$Id$</font>
+ </body>
+</html>
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