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 link…
The 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 the article.
The Usenet 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 name 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 statistics.