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4.5 KiB
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87 lines
4.5 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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<HEAD>
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<TITLE>What is Usenet, Anyway?</TITLE>
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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="node258.html">How Does Usenet Handle </A>
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<B>Up:</B> <A HREF="node255.html">Netnews</A>
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<B> Previous:</B> <A HREF="node256.html">Usenet History</A>
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<BR> <P>
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<H1><A NAME="SECTION0018200000">What <EM>is</EM> Usenet, Anyway?</A></H1>
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One of the most astounding facts about Usenet is that it isn't part of
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any organization, or has any sort of centralized network management
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authority. In fact, it's part of Usenet lore that except for a technical
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description, you cannot define <em>what</em> it is, you can only say what
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it isn't. If you have Brendan Kehoe's excellent ``Zen and the Art of the
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Internet'' (available online or through Prentice-Hall, see [<A HREF="#zen"></A>])
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at hand, you will find an amusing list of Usenet's non-properties.
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<P>
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At the risk of sounding stupid, one might define Usenet as a
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collaboration of separate sites who exchange Usenet news. To be a
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Usenet site, all you have to do is find another site Usenet site, and
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strike an agreement with its owners and maintainers to exchange news
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with you. Providing another site with news is also called <em>feeding</em>
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it, whence another common axiom of Usenet philosophy originates: ``Get a
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feed and you're on it.''
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<P>
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The basic unit of Usenet news is the article. This is a message a user
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writes and ``posts'' to the net. In order to enable news systems to deal
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with it, it is prepended with administrative information, the so-called
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article header. It is very similar to the mail header format laid down
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in the Internet mail standard RFC-822, in that it consists of several
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lines of text, each beginning with a field name terminated by a colon,
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which is followed by the field's value.<A HREF="footnode.html#8518"><IMG ALIGN=BOTTOM ALT="gif" SRC="foot_motif.gif"></A>
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<P>
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Articles are submitted to one or more <em>newsgroups</em>. One may
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consider a newsgroup a forum for articles relating to a common topic.
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All newsgroups are organized in a hierarchy, with each group's name
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indicating its place in the hierarchy. This often makes it easy to see
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what a group is all about. For example, anybody can see from the
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newsgroup name that comp.os.linux.announce is used for
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announcements concerning a computer operating system named .
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<P>
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These articles are then exchanged between all Usenet sites that are
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willing to carry news from this group. When two sites agree to exchange
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news, they are free to exchange whatever newsgroups they like to, and
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may even add their own local news hierarchies. For example,
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groucho.edu might have a news link to barnyard.edu, which
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is a major news feed, and several links to minor sites which it feeds
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news. Now, Barnyard College might receive all Usenet groups, while GMU
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only wants to carry a few major hierarchies like sci,
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comp, rec, etc. Some of the downstream sites, say a UUCP
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site called brewhq, will want to carry even fewer groups, because
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they don't have the network or hardware resources. On the other hand,
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brewhq might want to receive newsgroups from the fj
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hierarchy, which GMU doesn't carry. It therefore maintains another link
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with gargleblaster.com, who carry all fj groups, and feed
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them to brewhq. The news flow is shown in
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figure-<A HREF="node257.html#newsfigarticleflow"><IMG ALIGN=BOTTOM ALT="gif" SRC="cross_ref_motif.gif"></A>.
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<P>
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<P><A NAME="8697"></A><BR>
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<STRONG>Figure:</STRONG>
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<A NAME="newsfigarticleflow"></A>
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Usenet news flow through Groucho Marx University.
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<!--(tony: need .gif made from latex-fig flow.fig)-->
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<BR>
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<P>The labels on the arrows originating from brewhq may require some
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explanation, though. By default, it wants all locally generated news to
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be sent to groucho.edu. However, as groucho.edu does not
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carry the fj groups, there's no pointing in sending it any
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messages from those groups. Therefore, the feed from brewhq to
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GMU is labeled all,!fj, meaning that all groups except those
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below fj are sent to it.
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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="node258.html">How Does Usenet Handle </A>
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<B>Up:</B> <A HREF="node255.html">Netnews</A>
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<B> Previous:</B> <A HREF="node256.html">Usenet History</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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