Linux Network Administrator's Guide, Second Edition

How Does Usenet Handle News?

Today, Usenet has grown to enormous proportions. Sites that carry the whole of Netnews usually transfer something like a paltry 60 MB a day.^[122] Of course, this requires much more than pushing files around. So let’s take a look at the way most Unix systems handle Usenet news.

News begins when users create and post articles. Each user enters a message into a special application called a newsreader, which formats it appropriately for transmission to the local news server. In Unix environments the newsreader commonly uses the inews command to transmit articles to the newsserver using the TCP/IP protocol. But it’s also possible to write the article directly into a file in a special directory called the news spool. Once the posting is delivered to the local news server, it takes responsibility for delivering the article to other news users.

News is distributed through the net by various transports. The medium used to be UUCP, but today the main traffic is carried by Internet sites. The routing algorithm used is called flooding. Each site maintains a number of links (news feeds) to other sites. Any article generated or received by the local news system is forwarded to them, unless it has already been at that site, in which case it is discarded. A site may find out about all other sites the article has already traversed by looking at the Path: header field. This header contains a list of all systems through which the article has been forwarded in bang ...