USENET is a
directed graph. Each node in the graph is a host computer, each arc in the graph
is a transmission path from one host to another host. Each arc is labelled with
a newsgroup pattern, specifying which newsgroup classes are forwarded along that
sites receiving the incoming article examine it to make sure they really want
the article, accept it locally, and then in turn forward the article to all their
interested neighbors. This process continues until the entire network has seen
RFC 850; Standard for
Interchange of USENET Messages; Mark Horton;
is run by thousands of news servers that are accessed by client news
readers. At regular intervals, each news server connects to its partner
news servers, compares newsgroup databases, and exchanges any messages the other
server doesn't already have. A message posted to a single news server is therefore
quickly propagated completely around the Usenet in a very short time, typically
within a few minutes.
Like the Internet, the Usenet's distributed architecture
isn't dependent on any central administrative control, making it particularly
robust because it doesn't have a single point of failure. The entire network of
interconnected Usenet news servers is so large that the loss of individual news
servers does not significantly affect it.
The most common news server software
types are NNTP and INN.
It isn't unusual for more than one news server to operate at a given domain
if needed for different purposes. For a
variety of reasons, some sites provide public news servers.
Statistics. The following
sites provide statistics on the volume of Usenet traffic across their
news servers. Older stats are referenced from the page on historical