124 lines
5.6 KiB
HTML
124 lines
5.6 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
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<!--Converted with LaTeX2HTML 96.1-c (Feb 29, 1996) by Nikos Drakos (nikos@cbl.leeds.ac.uk), CBLU, University of Leeds -->
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<HTML>
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<!-- updated Sun Jul 14 20:10:00 MET DST 1996 by:
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Tony den Haan (tony@iaehv.nl) ftp://ftp.IAEhv.nl/pub/users/tony-->
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<HEAD>
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<TITLE>Pathalias and Map File Format</TITLE>
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</HEAD>
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<BODY LANG="EN">
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<A HREF="node1.html"><IMG WIDTH=65 HEIGHT=24 ALIGN=BOTTOM ALT="contents" SRC="contents_motif.gif"></A> <BR>
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<B> Next:</B> <A HREF="node195.html">Configuring elm</A>
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<B>Up:</B> <A HREF="node186.html">Electronic Mail</A>
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<B> Previous:</B> <A HREF="node193.html">Mixing UUCP and RFC-822</A>
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<BR> <P>
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<H1><A NAME="SECTION0015500000">Pathalias and Map File Format</A></H1>
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<A NAME="mailpathalias"></A> <A NAME="mailmaps"></A>
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The pathalias database provides the main routing information in
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UUCP-based networks. A typical entry looks like this (site name
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and path are separated by TABs):
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<PRE>
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moria.orcnet.org ernie!bert!moria!%s
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moria ernie!bert!moria!%s
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</PRE>
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This makes any message to moria be delivered via ernie
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and bert. Both moria's fully qualified name and its UUCP
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name have to be given if the mailer does not have a separate way to
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map between these name spaces.
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<P>
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If you want to direct all messages to hosts inside some domain to its
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mail relay, you may also specify a path in the pathalias database,
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giving the domain name as target, preceded by a dot. For example, if
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all hosts in the sub.org may be reached through
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swim!smurf, the pathalias entry might look like this:
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<PRE>
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\&.sub.org swim!smurf!%s
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</PRE>
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Writing a pathalias file is acceptable only when you are running a site
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that does not have to do much routing. If you have to do routing for a
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large number of hosts, a better way is to use the pathalias command
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to create the file from map files. Maps can be maintained much easier,
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because you may simply add or remove a system by editing the system's map
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entry, and re-create the map file. Although the maps published by the
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Usenet Mapping Project aren't used for routing very much anymore, smaller
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UUCP networks may provide routing information in their own set of maps.
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<P>
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A map file mainly consists of a list of sites, listing the sites
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each system polls or is polled by. The system name begins in column
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one, and is followed by a comma-separated list of links. The list may
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be continued across newlines if the next line begins with a tab. Each
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link consists of the name of the site, followed by a cost given in
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brackets. The cost is an arithmetic expression, made up of numbers and
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symbolic costs. Lines beginning with a hash sign are
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ignored.
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<P>
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As an example, consider moria, which polls swim.twobirds.com
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twice a day, and bert.sesame.com once per week. Moreover, the link
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to bert only uses a slow 2400bps modem. moria's would publish
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the following maps entry:
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<PRE>
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moria.orcnet.org
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bert.sesame.com(DAILY/2),
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swim.twobirds.com(WEEKLY+LOW)
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moria.orcnet.org = moria
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</PRE>
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The last line would make it known under its UUCP name, too. Note that
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it must be DAILY/2, because calling twice a day actually
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halves the cost for this link.
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<P>
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Using the information from such map files, pathalias is able to
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calculate optimal routes to any destination site listed in the paths
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file, and produce a pathalias database from this which can then be used
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for routing to these sites.
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<P>
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<A NAME="7173"></A>
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pathalias provides a couple of other features like site-hiding
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(i.e. making sites accessible only through a gateway) etc. See the
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manual page for pathalias for details, as well as a complete list
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of link costs.
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<P>
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Comments in the map file generally contain additional information on
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the sites described in it. There is a rigid format in which to specify
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this, so that it can be retrieved from the maps. For instance, a
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program called uuwho uses a database created from the map files
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to display this information in a nicely formatted way.
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<P>
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When you register your site with an organization that distributes map files
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to its members, you generally have to fill out such a map entry.
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<P>
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Below is a sample map entry (in fact, it's the one for my site):
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<PRE>
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#N monad, monad.swb.de, monad.swb.sub.org
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#S AT 486DX50; Linux 0.99
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#O private
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#C Olaf Kirch
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#E okir@monad.swb.de
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#P Kattreinstr. 38, D-64295 Darmstadt, FRG
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#L 49 52 03 N / 08 38 40 E
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#U brewhq
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#W okir@monad.swb.de (Olaf Kirch); Sun Jul 25 16:59:32 MET DST
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#
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monad brewhq(DAILY/2)
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# Domains
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monad = monad.swb.de
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monad = monad.swb.sub.org
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</PRE>
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The white space after the first two characters is a TAB. The meaning of
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most of the fields is pretty obvious; you will receive a detailed
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description from whichever domain you register with. The L
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field is the most fun to find out: it gives your geographical position
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in latitude/longitude and is used to draw the postscript maps that show
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all sites for each country, as well as world-wide.<A HREF="footnode.html#7174"><IMG ALIGN=BOTTOM ALT="gif" SRC="foot_motif.gif"></A>
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<P>
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<HR><A HREF="node1.html"><IMG WIDTH=65 HEIGHT=24 ALIGN=BOTTOM ALT="contents" SRC="contents_motif.gif"></A> <BR>
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<B> Next:</B> <A HREF="node195.html">Configuring elm</A>
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<B>Up:</B> <A HREF="node186.html">Electronic Mail</A>
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<B> Previous:</B> <A HREF="node193.html">Mixing UUCP and RFC-822</A>
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<P><ADDRESS>
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<I>Andrew Anderson <BR>
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Thu Mar 7 23:22:06 EST 1996</I>
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</ADDRESS>
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</BODY>
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</HTML>
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