USENET is made up of many subnetworks. Each subnet has a name, such as ‘net’ or ‘btl’… Each subnet is a connected graph, that is, a path exists from every node to every other node in the subnet. In addition, the entire graph is (theoretically) connected. (In practice, some political considerations have caused some sites to be unable to post articles reaching the rest of the network.).
The Usenet is run by thousands of news servers that exchange millions of messages each day, distributing new postings so each newsgroup looks about the same from anywhere in the world. This simple but powerful technology makes the Usenet the first peer-to-peer Internet technology, a model later adopted with great success by the original infamous Napster music sharing site and other file distribution services. The following sections provide more information: