Unison makes it easier to access Usenet than ever before, but for best results, it's good to have some familiarity with Usenet's history.
Developed in the 1970s, Usenet was one of the earliest communities on the internet. Many Usenet concepts found their way into later social networks, such as bulletin board systems and web forums.
Despite its age, Usenet remains a popular destination for both discussion and file postings.
To browse and post to Usenet, you need both a client program (such as Unison) and an active account on a Usenet server.
Some internet service providers (ISPs) include access to Usenet with your other account services. You should check with your ISP to see if Usenet access is included, and if so, what your login credentials are.
If you don't already have access to a Usenet server, many commercial servers are available for a monthly fee. One such server is our own Unison Access.
It's important to understand that there is no central Usenet server. Each individual server propagates its messages to other servers, until finally the message is available (theoretically) from any server that carries the newsgroup. This means that at any point in time, different Usenet servers may contain different portions of the overall Usenet content.
Things posted to Usenet do not last forever. Because of the tremendous amount of data posted to Usenet every day, messages eventually expire and begin disappearing from servers. Exactly how long this takes depends on the server. Usenet service providers refer to this as "retention". Messages expired from one server may still be available on another server that has better retention.
Usenet was initially created for the exchange of text-based discussion, however users soon came up with ways to share files using the network as well. Since Usenet is only capable of handling text-based messages, any files must go through an "encoding" process, which turns them into a series of text messages. The reader on the receiving side then decodes and joins the messages back into the original file.
Fortunately, Unison takes care of this entire encoding, decoding, and joining process for you, so all you see are regular files that you can download just as you would from a web site.
Newsgroups: Usenet is divided into separate, independent topic areas, called newsgroups.
PAR Set: PAR (for "parity") is a file format that allows reconstruction of missing file parts. If some parts of a file post are missing, but enough of the file's PAR set is present, you may be able to rebuild the missing parts.
Parts: When a large file is posted to Usenet, it is usually split into multiple smaller parts to facilitate transmission throughout the network. You must have access to all the individual parts to download the file. In some cases, if your server is missing parts, you may be able to reconstruct them by downloading the file's PAR set as well.
Retention: A measure of how long posts remain on a particular Usenet server before expiring.