One of the most astounding facts about Usenet is that it isn't part of
any organization, nor does it have any sort of centralized network management
authority. In fact, it's part of Usenet lore that except for a technical
description, you cannot define what it is; at the risk of sounding stupid, one might define Usenet as a collaboration
of separate sites that exchange Usenet news. To be a Usenet site, all you
have to do is find another Usenet site and strike an agreement with its
owners and maintainers to exchange news with you. Providing another site
with news is called feeding it, whence another
common axiom of Usenet philosophy originates: “Get a feed, and you're
on it.”
The basic unit of Usenet news is the
article. This is a message a user writes and
“posts” to the net. In order to enable news systems to
deal with it, it is prepended with administrative information, the
so-called article header. It is very similar to the mail header format
laid down in the Internet mail standard RFC-822, in that it consists
of several lines of text, each beginning with a field name terminated
by a colon, which is followed by the field's value.[1]
Articles are submitted to one or more newsgroup. One may
consider a newsgroup a forum for articles relating to a common topic. All
newsgroups are organized in a hierarchy, with each group's name indicating
its place in the hierarchy. This often makes it easy to see what a group is
all about. For example, anybody can see from the newsgroup name that
comp.os.linux.announce is used for
announcements concerning a computer operating system named Linux.
These articles are then exchanged between all Usenet sites that are
willing to carry news from this group. When two sites agree to exchange
news, they are free to exchange whatever newsgroups they like, and
may even add their own local news hierarchies. For example,
groucho.edu might have a news link
to barnyard.edu, which
is a major news feed, and several links to minor sites which it feeds
news. Now Barnyard College might receive all Usenet groups, while GMU
only wants to carry a few major hierarchies like
sci,
comp, or
rec. Some of the downstream
sites, say a UUCP site called brewhq,
will want to carry even fewer groups, because they don't have the network or
hardware resources. On the other hand,
brewhq might want to receive
newsgroups from the fj
hierarchy, which GMU doesn't carry. It therefore maintains another link
with gargleblaster.com, which carries
all fj groups and feeds
them to brewhq. The news flow is
shown in Figure 20-1.
The labels on the arrows originating from
brewhq may require some explanation,
though. By default, it wants all locally generated news to be sent to
groucho.edu. However, as
groucho.edu does not carry the
fj groups, there's no point in
sending it any messages from those groups. Therefore, the feed from
brewhq to GMU is labeled
all,!fj, meaning that all groups
except those below fj are sent to it.
