An introduction to AUN

When Acorn originally released the BBC micro it had the capability to be networked using Acorn's own networking system, Econet. This was commonly used to share the then-expensive printers and disc drives (both floppy and 'Winchester' hard drives).

When the Archimedes series was launched Acorn retained the Econet network system, and all the Archimedes series machines (other than the the A3010) could be upgraded with a plug-in board. This gave access to the same network facilities present on the BBC Micro.

The Acorn Fileserver protocol was used to allow BBC and Archimedes machines to access files stored on a fileserver. The user would login with their username and password and would be able to use their own area of the fileserver disc. In a similar way the Printer Server Protocol allowed a network user to print to a printer on a remote machine, sharing with other users.

Both Acorn and SJ Research produced a range of file server and printer server solutions. The most common were the SJ Research MDFS, a stand alone server box that connected to an Econet network and offered file and print serving, and the Acorn Level 4 fileserver, which allowed an Archimedes machine to act as a file server and / or a printer server.

Several other products made use of the networking abilities of both the BBC and Archimedes. These included teletext page servers, terminal connections, databases and even games.

As application and data sizes grew, the original Econet system was pushed to its limits. While it was adequate for transferring the relatively small amount of data used by the BBC, as the Archimedes started to use megabytes, Econet was just too slow.

Newer networking technologies allowed data to be moved around much quicker than on Econet. Whereas an Econet network was limited to around 200kbits a second, an Ethernet could run up to 10 megabits a second - 50 times as fast!

Although ethernet was already available on the Archimedes to talk to TCP/IP networks, usually with Unix servers, most users still wanted to be able to run all their existing Econet-based applications. Acorn Universal Networking was the way this was effected.

The term "AUN" has had many meanings in the past, but what we today call "AUN" in RISC OS Select is a way to allow these Econet-based applications to be run over an TCP/IP network (typically Ethernet).

What's in AUN?

AUN in RISC OS Select consists of a number of ROM modules and supporting disc files and scripts. These are configured using configuration plugins.

There are two main aspects to what is provided. There is the AUN system itself - the way that Econet-based applications can run - and there are the file and print server clients.

Econet Station Numbering

An Econet network was made up of a number of stations. Two networks could be connected by means of a Bridge. Each computer connected was uniquely identified by two numbers. The first was the station number, which could be between 1 and 254, the second was the network number, which could be between 1 and 127.

Translating that to TCP/IP

AUN uses a TCP/IP network to provide the same facilities as Econet. Because applications expect to be able to reference a station using the net and station numbers, these must be "mapped" onto IP addresses. This mapping defines what IP address ranges are used for an econet network.

To avoid clashes on machines that have both an ethernet and an econet interface the network number of an AUN station must be between 128 and 251.

The AUN Map file controls the translation between the network number and IP address. For example, if your network runs on the private IP range of 192.168.0.x, you may want to map this to AUN network 128. This will mean the machine with the IP has an AUN address of 128.1.

Setting up AUN

The "AUN" plugin in the !Configure "Networking" section allows the AUN system to be set up.

The first option is "Enable AUN" - this control wether or not the AUN system is activated. If you wish to use any Econet-based network applications over an ethernet network you will need to enable this.

The current AUN network map is shown below this. The buttons at the side are used to edit the values in the AUN map. The "Auto-configure AUN maps for local interfaces" option provides a quick and easy way of setting up a simple AUN system. It will automatically map each local ethernet interface to a AUN network, based on that interface's IP address. Often, this will give a fully functional AUN system without the need for the AUN Map files.

The automatic configuration of AUN maps will ignore any link local addresses which are allocated to interfaces.

Finally, the current contents of the AUN Map file can be saved by dragging the icon to a filer window, or a saved map loaded by dragging it to the box. This allows a map file to be setup on one computer and quickly installed on several others.


Earlier we mentioned the file and printer server clients. The "NetFS" plugin allows us to use these.

Level 4, or Advanced Level 4, allows an Archimedes or RiscPC to act as a file server to an AUN network, providing a password controlled storage area and spooled printer facilities. While these products are not provided by RISC OS ltd, the clients to provide access to them are.

The file server client provides NetFS and a "Net" icon on the iconbar that allows connections to be made to servers, the printer server client allows the connection of "Net" to be selected in !Printers, allowing print jobs to be sent to printer server machines which share one or more printers.

To enable these clients, the "Use NetFS and NetPrint" option should be enabled. The file server and print server options allow the default file and printer servers to be set. The default file server will appear in the logon box when the "Net" icon is clicked.

The "Use ArthurLib" option allows Archimedes and BBC machines to have separate "Library" directories on the fileserver. It's usually left on.

This documentation is copyright 3QD Developments Ltd 2013 and may not be reproduced or published in any form without the copyright holders permission. RISC OS is subject to continuous development and improvement as such all information is reproduced by 3QD Developments Ltd in good faith and is believed to be correct at the time of publication E&OE. 3QD Developments Ltd cannot accept any liability for any loss or damage arising from the use of any information provided as part of the RISC OS Documentation.

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