Sites that carry the whole of Netnews usually transfer something like a paltry 60 MB a day. 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. But it's also possible to write the article directly into a file in a special directory called the news spool.
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 . 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. The flow between any two sites may be limited by two criteria. On the other hand, the newsgroups exchanged may be limited by both the sending and receiving systems.