321 lines
6.2 KiB
HTML
321 lines
6.2 KiB
HTML
<HTML
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><HEAD
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><TITLE
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>What Is Usenet, Anyway?</TITLE
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><META
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NAME="GENERATOR"
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CONTENT="Modular DocBook HTML Stylesheet Version 1.57"><LINK
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REL="HOME"
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TITLE="Linux Network Administrators Guide"
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HREF="index.html"><LINK
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REL="UP"
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TITLE="Netnews"
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HREF="x-087-2-news.html"><LINK
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REL="PREVIOUS"
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TITLE="Usenet History"
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HREF="x-087-2-news.history.html"><LINK
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REL="NEXT"
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TITLE="How Does Usenet Handle News?"
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HREF="x-087-2-news.algorithm.html"></HEAD
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><TR
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><TH
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COLSPAN="3"
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>Linux Network Administrators Guide</TH
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></TR
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><TR
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><TD
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WIDTH="10%"
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ALIGN="left"
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><A
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HREF="x-087-2-news.history.html"
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>Prev</A
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></TD
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><TD
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WIDTH="80%"
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ALIGN="center"
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VALIGN="bottom"
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>Chapter 20. Netnews</TD
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><TD
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WIDTH="10%"
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ALIGN="right"
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VALIGN="bottom"
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><A
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HREF="x-087-2-news.algorithm.html"
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>Next</A
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></TD
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></TR
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></TABLE
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><HR
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ALIGN="LEFT"
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WIDTH="100%"></DIV
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><DIV
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CLASS="SECT1"
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><H1
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CLASS="SECT1"
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><A
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NAME="X-087-2-NEWS.USENET"
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>20.2. What Is Usenet, Anyway?</A
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></H1
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><P
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>
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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, nor does it have 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 <I
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CLASS="EMPHASIS"
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>what</I
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> it is; at the risk of sounding stupid, one might define Usenet as a collaboration
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of separate sites that exchange Usenet news. To be a Usenet site, all you
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have to do is find another Usenet site and strike an agreement with its
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owners and maintainers to exchange news with you. Providing another site
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with news is called <I
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CLASS="EMPHASIS"
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>feeding</I
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> it, whence another
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common axiom of Usenet philosophy originates: “Get a feed, and you're
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on it.”</P
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><P
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>
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The basic unit of Usenet news is the
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<I
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CLASS="EMPHASIS"
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>article</I
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>. This is a message a user writes and
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“posts” to the net. In order to enable news systems to
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deal with it, it is prepended with administrative information, the
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so-called article header. It is very similar to the mail header format
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laid down in the Internet mail standard RFC-822, in that it consists
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of several lines of text, each beginning with a field name terminated
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by a colon, which is followed by the field's value.<A
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NAME="X-087-2-FNUN01"
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HREF="#FTN.X-087-2-FNUN01"
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>[1]</A
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> </P
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><P
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>
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Articles are submitted to one or more <I
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CLASS="EMPHASIS"
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>newsgroup</I
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>. One may
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consider a newsgroup a forum for articles relating to a common topic. All
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newsgroups are organized in a hierarchy, with each group's name indicating
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its place in the hierarchy. This often makes it easy to see what a group is
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all about. For example, anybody can see from the newsgroup name that
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<SPAN
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CLASS="SYSTEMITEM"
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>comp.os.linux.announce</SPAN
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> is used for
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announcements concerning a computer operating system named Linux.</P
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><P
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>
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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, and
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may even add their own local news hierarchies. For example,
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<SPAN
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CLASS="SYSTEMITEM"
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>groucho.edu</SPAN
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> might have a news link
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to <SPAN
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CLASS="SYSTEMITEM"
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>barnyard.edu</SPAN
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>, 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
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<SPAN
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CLASS="SYSTEMITEM"
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>sci</SPAN
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>,
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<SPAN
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CLASS="SYSTEMITEM"
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>comp</SPAN
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>, or
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<SPAN
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CLASS="SYSTEMITEM"
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>rec</SPAN
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>. Some of the downstream
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sites, say a UUCP site called <SPAN
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CLASS="SYSTEMITEM"
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>brewhq</SPAN
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>,
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will want to carry even fewer groups, because they don't have the network or
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hardware resources. On the other hand,
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<SPAN
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CLASS="SYSTEMITEM"
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>brewhq</SPAN
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> might want to receive
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newsgroups from the <SPAN
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CLASS="SYSTEMITEM"
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>fj</SPAN
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>
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hierarchy, which GMU doesn't carry. It therefore maintains another link
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with <SPAN
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CLASS="SYSTEMITEM"
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>gargleblaster.com</SPAN
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>, which carries
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all <SPAN
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CLASS="SYSTEMITEM"
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>fj</SPAN
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> groups and feeds
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them to <SPAN
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CLASS="SYSTEMITEM"
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>brewhq</SPAN
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>. The news flow is
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shown in <A
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HREF="x-087-2-news.usenet.html#X-087-2-NEWS.FIG.ARTICLE-FLOW"
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>Figure 20-1</A
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>.</P
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><DIV
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CLASS="FIGURE"
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><A
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NAME="X-087-2-NEWS.FIG.ARTICLE-FLOW"
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></A
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><P
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><B
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>Figure 20-1. Usenet newsflow through Groucho Marx University</B
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></P
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><P
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><IMG
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SRC="lag2_2001.jpg"></P
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></DIV
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><P
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>The labels on the arrows originating from
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<SPAN
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CLASS="SYSTEMITEM"
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>brewhq</SPAN
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> may require some explanation,
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though. By default, it wants all locally generated news to be sent to
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<SPAN
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CLASS="SYSTEMITEM"
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>groucho.edu</SPAN
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>. However, as
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<SPAN
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CLASS="SYSTEMITEM"
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>groucho.edu</SPAN
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> does not carry the
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<SPAN
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CLASS="SYSTEMITEM"
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>fj</SPAN
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> groups, there's no point in
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sending it any messages from those groups. Therefore, the feed from
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<SPAN
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CLASS="SYSTEMITEM"
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>brewhq</SPAN
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> to GMU is labeled
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<TT
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CLASS="LITERAL"
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>all,!fj</TT
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>, meaning that all groups
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except those below <SPAN
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CLASS="SYSTEMITEM"
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>fj</SPAN
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> are sent to it.</P
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></DIV
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><H3
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CLASS="FOOTNOTES"
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>Notes</H3
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><TABLE
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BORDER="0"
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CLASS="FOOTNOTES"
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WIDTH="100%"
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><TR
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><TD
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ALIGN="LEFT"
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VALIGN="TOP"
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WIDTH="5%"
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><A
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NAME="FTN.X-087-2-FNUN01"
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HREF="x-087-2-news.usenet.html#X-087-2-FNUN01"
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>[1]</A
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></TD
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><TD
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ALIGN="LEFT"
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VALIGN="TOP"
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WIDTH="95%"
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><P
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> The format of Usenet news messages is
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specified in RFC-1036, “Standard for interchange of USENET
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messages.”</P
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></TD
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></TR
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></TABLE
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><DIV
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CLASS="NAVFOOTER"
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><HR
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ALIGN="LEFT"
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WIDTH="100%"><TABLE
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WIDTH="100%"
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BORDER="0"
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CELLPADDING="0"
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CELLSPACING="0"
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><TR
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><TD
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WIDTH="33%"
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ALIGN="left"
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VALIGN="top"
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><A
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HREF="x-087-2-news.history.html"
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>Prev</A
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></TD
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><TD
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WIDTH="34%"
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ALIGN="center"
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VALIGN="top"
|
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><A
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HREF="index.html"
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>Home</A
|
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></TD
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><TD
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WIDTH="33%"
|
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ALIGN="right"
|
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VALIGN="top"
|
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><A
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HREF="x-087-2-news.algorithm.html"
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>Next</A
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></TD
|
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></TR
|
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><TR
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><TD
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WIDTH="33%"
|
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ALIGN="left"
|
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VALIGN="top"
|
|
>Usenet History</TD
|
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><TD
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WIDTH="34%"
|
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ALIGN="center"
|
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VALIGN="top"
|
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><A
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HREF="x-087-2-news.html"
|
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>Up</A
|
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></TD
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><TD
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WIDTH="33%"
|
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ALIGN="right"
|
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VALIGN="top"
|
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>How Does Usenet Handle News?</TD
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></TR
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></TABLE
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></DIV
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></BODY
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></HTML
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> |