Econet was Acorn Computers's low-cost local area network system, intended for use by schools and small businesses.

Econet
ANB22 BBC Econet Upgrade manuals.jpg
Econet upgrade manuals
DeveloperAcorn Computers
ManufacturerAcorn Computers
TypeComputer networking
Generation8-bit
Release date1981 (1981)
Operating systemMOS

Econet software was mostly superseded by AUN, though some suppliers were still offering bridging kits to interconnect old and new networks.[1][2] In turn, AUN was superseded by the Acorn Access+ software.[3] Support for Econet was removed from the Linux kernel at version 3.5 in 2012, because of lack of use and privilege escalation vulnerabilities.[4][5]

Implementation historyEdit

Econet was specified in 1980, and first developed for the Acorn Atom and Acorn System 2/3/4 computers in 1981.[6][7] Also in that year the BBC Microcomputer was released, initially with provision for floppy disc and Econet interface ports, but without the necessary supporting ICs fitted, optionally to be added in a post sale upgrade.[8]

In 1982, the Tasmania Department of Education requested a tender for the supply of personal computers to their schools. Earlier that year Barson Computers, Acorn's Australian computer distributor, had released the BBC Microcomputer with floppy disc storage as part of a bundle. Acorn's Hermann Hauser and Chris Curry agreed to allow it to be also offered with Econet fitted, as they had previously done with the disc interface. As previously with the Disc Filing System, they stipulated that Barson would need to adapt the network filing system from the System 2 without assistance from Acorn. Barson's engineers applied a few modifications to fix bugs on the early BBC Micro motherboards, which were adopted by Acorn in later releases. With both floppy disc and networking available, the BBC Micro was approved for use in schools by all state and territory education authorities in Australia and New Zealand, and quickly overtook the Apple II as the computer of choice in private schools.

With no other supporting documentation available, the head of Barson's Acorn division, Rob Napier, published Networking with the BBC Microcomputer,[9] the first reference documentation for Econet.

Econet was officially released for the BBC Micro in the UK in 1984, and it later became popular as a networking system for the Acorn Archimedes. Econet was eventually officially supported on all post-Atom Acorn machines,[10][11] apart from the Electron (except in Australia and New Zealand where Barson Computers built their own Econet daughter board[12]), along with 3rd party ISA cards for the IBM PC. The "Ecolink" ISA interface card for IBM-compatible PCs was available.[13] It used Microsoft's MS-NET Redirector for MS-DOS to provide file and printer sharing via the NET USE command.

File, Print and Tape servers, for the architecture were also supplied by 3rd party vendors such as S J Research.[14]

Econet was supported by Acorn MOS, RISC OS, RISC iX, FreeBSD and Linux operating systems.[15]

Acorn once received an offer from Commodore International to license the technology, which it refused.[16]

Subsequent developmentEdit

With the falling prices and widespread adoption of IP networking in the early 1990s, Acorn Universal Networking (AUN),[17] an implementation of Econet protocols and addressing over TCP/IP (in Acorn's words "an AUN network is a conformant TCP/IP network underneath the Econet-like veneer"[18]), was developed to provide legacy support for Econet on Ethernet-connected machines.[19]

The Econet protocol and AUN were also supported by the Linux kernel.[5]

Supported systemsEdit

Econet was supported by a large number of different computer and server systems, produced both by Acorn and by other companies. As well as Acorn's MOS and RISC OS these also used other operating systems such as CP/M, DR-DOS, Unix, Linux or Microsoft Windows.

The Econet API includes an Econet_MachinePeek command, which can be used by software to determine if a machine is present on the network and its hardware platform. The machine-type codes which can be returned by that command[20][21] are a useful indication of the range of hardware that offered Econet as their primary networking function or as an option:

Code Machine type
&0000 Reserved
&0001 Acorn BBC Micro Computer (OS 1 or OS 2)
&0002 Acorn Atom
&0003 Acorn System 3 or System 4
&0004 Acorn System 5
&0005 Acorn Master 128 (OS 3)
&0006 Acorn Electron (OS 0)
&0007 Acorn Archimedes (OS 6)
&0008 Reserved for Acorn
&0009 Acorn Communicator
&000A Acorn Master 128 Compact Econet Terminal
&000B Acorn Filestore
&000C Acorn Master 128 Compact (OS 5)
&000D Acorn Ecolink card for Personal Computers
&000E Acorn Unix Workstation
&000F to &FFF9 Reserved (see below for later allocations)
&FFFA SCSI Interface
&FFFB SJ Research IBM PC Econet interface
&FFFC Nascom 2
&FFFD Research Machines 480Z
&FFFE SJ Research File Server
&FFFF Z80 CP/M

The manual[21] includes an assembly language program to report a machine type, software version and release numbers.

An update to the list in volume 5A of the PRM[22] lists the following additions to the table above:

Code Machine type
&000F RISC PC architecture
&0010 to &FFF7 Reserved
&FFF8 SJ Research GP server
&FFF9 SJ Research 80386 UNIX

Physical and data-link layersEdit

Econet DIN-5 pinout
 
1 Data (+ve)
2 Ground
3 Clock (+ve)
4 Data (-ve)
5 Clock (-ve)

Econet is a five-wire bus network. One pair of wires is used for the clock, one pair for data, and one wire as a common ground. Signalling used the RS-422 5-volt differential standard, with one bit transferred per clock cycle. Unshielded cable was used for short lengths, and shielded cable for longer networks. The cable was terminated at each end to prevent reflections and to guarantee high logic levels when the bus was undriven.

The original connectors were five-pin circular 180° DIN types. On later 32-bit machines (notably the A3020 and A4000), the Econet connection was made via five of the pins on their 15-pin D-type Network port, which could also accept MAUs (Media Attachment Units) to allow other types of network to be connected via the same socket. This port looks similar to an AUI port, but is not compatible.[citation needed]

The Acorn A4 laptop used another implementation, in the form of a 5 pin mini-DIN.[23]

Each Econet interface was controlled by a Motorola MC68B54 Advanced Data Link Controller (ADLC) chip, which handled electrical transmission/reception, frame checksumming and collision detection.[24]

 
Acorn A4 - ALA66 Econet module

Network and transport layersEdit

Econet used a connectionless transmission model, similar to UDP, with no checksumming or error correction at this layer. Each packet had a four byte header consisting of:

  1. The destination station number
  2. The destination network number
  3. The source station number
  4. The source network number

A single data transmission consisted of four frames, each with a header as above:

  1. The sending station sends a scout packet with a port number and a flag byte
  2. The addressed receiving station returns a scout acknowledge to the sender
  3. The sending station sends the data
  4. The receiving station finishes with a final acknowledge, identical to the scout acknowledge

There was provision for broadcast transmissions, a single frame sent with its destination station and network numbers set to 255. There was also provision for promiscuous mode reception, termed wild receive in the PRM, requested by listening for station and network numbers both being zero.

Technical details of packets and frames, the Econet API, and worked examples in ARM assembler and BBC BASIC are given in the RISC OS Programmer's Reference Manual.[25]

Network servicesEdit

At the time and in the markets for which Econet was developed, the main purpose of computer networking was to provide local area shared access to expensive hardware such as disc storage and printers. Acorn provided software for the BBC Micro to implement a file server, and optionally a printer server also. The original file server was very basic, essentially allowing limited access to a floppy disc over the network. The server software was further developed over many years, and Acorn and other manufacturers also produced dedicated Econet servers based on various technologies. So the servers available fell into roughly three categories:[26]

  • The Acorn Fileserver, from Level 1 through Level 4, running on a standard computer (BBC, Master or Archimedes) and providing simple file and print services.[27][28]
  • The dedicated Acorn Filestore units, running on dedicated hardware with higher capacity and more facilities.[29]
  • Third party units (notably from SJ Research), again running on dedicated hardware and with their own implementations of the server software. These were compatible with the Acorn implementations, but with additional enhancements. (Notably, Oak Solutions collaborated with Acorn to develop the Level 4 Fileserver solution.[28])

The machine type numbers listed in the "Supported systems" section above are an indication of the range of hardware that was available or planned.

Additional services could be implemented, using the network API provided. Short utilities such as network chat programs were often published in magazines or distributed by sharing among users; these made use of the Econet protocols to work alongside the basic file and print services. Larger software packages (some of them commercial) were available that provided services such as Teletext and modem drivers.[30]

FilestoreEdit

Acorn emphasised the Filestore in the late 1980s as a solution for small workgroups,[31] offering a base unit with optional hard disk storage modules.[29] The Filestore was a 65C102-based machine with 64 KB of RAM and 64 KB of ROM having Econet connectivity, two 3.5" floppy drives, a parallel printer interface, expansion bus, Econet clock and termination circuits, a real-time clock, and a quantity of battery-backed RAM.[32] The battery-backed RAM was used to hold configuration and authentication details.[33]

Initially, hard disk expansion was offered in the form of the E20 module providing a 3.5" 20 MB Winchester disk drive for the E01 base unit;[32] later expansions in the form of the E40S and E60S provided 40 MB and 60 MB storage respectively for the E01S base unit.[29] The "S" suffix reportedly signifies that the units are "stacking".[33]

FileserverEdit

Acorn also offered the Level 1,[32] Level 2 and Level 3 Fileserver solutions running on sufficiently upgraded BBC Micro or BBC Master computers.[34] The Level 1 product offered access to existing Acorn DFS discs via a BBC Model B with Econet, disc interface and single or dual drives. Level 2 elevated the requirements to include a 6502 second processor but provided hierarchical storage with the number of files limited only by the amount of storage available, plus enhanced access controls, random access to data files, and authentication support.[27] Level 3 introduced Winchester hard drive support.[32]

With the release of the Level 4 Fileserver software providing a means to "extend the life of existing Acorn computers, such as the A310",[28] the emphasis had evidently shifted away from the Filestore and towards the Level 4 product at the start of the 1990s.[35] A base Filestore E01S unit had a price inclusive of VAT of £1148.85 in February 1989, whereas an Archimedes 310 with 1 MB of RAM cost only £958.00 and an Econet module £56.35, illustrating the pricing considerations for potential buyers.[36] By 1991, the Filestore was apparently no longer offered in Acorn's pricing (nor was the A310), but the Level 4 software was priced at £233.83 and an Archimedes 410/1 with 1 MB of RAM at £1049.33.[37]

Unix system servicesEdit

With the introduction of Acorn's Unix workstations running RISC iX, an envisaged application for Econet was the use of Master 128 computers acting as terminals to these Unix systems.[31](pp4) Such systems also offered the capability to act as bridges between Econet and Ethernet networks, offering routing facilities to any Unix machines attached to the Econet,[31](pp5) this being enabled by the IP-over-Econet support in RISC iX.[38]

X.25 network servicesEdit

An Econet X.25 gateway product was offered by Acorn, providing access to X.25 networks for computers on an Econet, with the X25 Terminal ROM and the existing Acorn DNFS ROM needing to be fitted to computers to enable access to X.25 services, with the Terminal ROM providing terminal emulation and file transfer functionality.[39]

The gateway hardware consisted of the core functionality of a BBC Micro, this being the network service module connected to the Econet, combined with a Z80 second processor connected via the Tube interface, this acting as the gateway module and having 16 KB ROM and 32 KB of private RAM, augmented by another board with a Z80 processor with 32 KB of private RAM, this being the X25 module accessing the X.25 line. The gateway and X25 modules communicated via 16 KB of dual-ported shared RAM. The X25 module was designed by Symicron and ran the "proven" Symicron Telematics Software (STS).[40]

Econet users would send network service requests to the gateway that would be forwarded by the STS functionality of the gateway to the X.25 network. Incoming X.25 calls would be forwarded by the STS functionality to the network service functionality and on to the Econet. Network service requests could employ X.25, Yellow Book Transport Service, and X.29 protocols.[41]

Comparison with modern systemsEdit

While Econet was essentially specific to the Acorn range of computers, it does share common concepts with modern network file systems and protocols:

  • Remote Procedure Call – Almost all network operations were performed via a primitive remote procedure call system, either by passing a command line direct to the file server, or by passing an operating system call parameter block. The logon command *I AM was processed by passing the whole command line and reading back the result code.
  • Access Permissions – By the time of the Acorn Level 4 File Server and the SJ Research MDFS systems, Econet file servers had a full user name and password system with public and private attributes. These worked similar to Unix permissions without the group field. Files could be set to be readable and/or writable by everyone, just by the user, or both.
  • Subnetting – A basic Econet would be a single network segment, which is usually assumed to be network 0. With the use of one or more bridges, it is possible to have up to 127 Econet segments with up to 254 hosts each, for a maximum of 32,258 possible machines.
  • Broadcasting – By using host 255, an Econet host could send broadcast packets to all hosts on the network segment. Later implementations of the client software used this to automatically locate file and printer servers.
  • Printer Spooling – Later versions of the Econet printer server software used printer spooling to locally cache print jobs before sending to the remote printer. This ensured whole print jobs were sent to the printer in one go.
  • Ports – Because the various protocols (file and printer servers, bridge discovery, and so forth) used defined port numbers,[42][43][44] it was possible to for additional services such as BroadcastLoader, AppFS, a teletext server, and a range of chat programs and multiplayer games to coexist within the Econet system.

See alsoEdit

ReferencesEdit

  1. ^ "CJEMicro Networking and Broadband". 2018. Retrieved 14 November 2018. CS1 maint: discouraged parameter (link)
  2. ^ "BeebMaster Beebshop". 2018. Retrieved 14 November 2018. CS1 maint: discouraged parameter (link)
  3. ^ "Acorn Access+ User Guide" (PDF). Acorn Computers. 1994. Retrieved 26 November 2014. CS1 maint: discouraged parameter (link)
  4. ^ Hemminger, Stephen (18 May 2012). "Econet: Remove Ancient Bug Ridden Protocol". Archived from the original on 9 July 2012. Retrieved 18 May 2012. CS1 maint: discouraged parameter (link)
  5. ^ a b Corbet, Jonathan (23 May 2012). "The 3.5 Merge Window Opens". LWN.net. Retrieved 24 November 2014. CS1 maint: discouraged parameter (link)
  6. ^ "Retro Isle - Acorn Econet". www.retroisle.com. Retrieved 2020-10-28.
  7. ^ "Chris's Acorns: Econet". chrisacorns.computinghistory.org.uk. Retrieved 2020-10-28.
  8. ^ "BBC Micro Model B Econet Interface". www.retro-kit.co.uk. Retrieved 2020-10-28.
  9. ^ Napier, Robert G. (1984). Networking with the BBC Microcomputer. Prentice-Hall. ISBN 978-0-13-611468-0.
  10. ^ "Networking". www.apdl.org.uk. Retrieved 2020-10-28.
  11. ^ "BeebMaster - I Want an Econet!". www.beebmaster.co.uk. Retrieved 2020-10-28.
  12. ^ "Acorn Electron Econet Interface". BeebMaster. Retrieved 27 September 2020.
  13. ^ "PC Econet Interface". beebmaster.co.uk. Retrieved 25 November 2014. CS1 maint: discouraged parameter (link)
  14. ^ "SJ Research MDFS - Econet File Server - Peripheral - Computing History". www.computinghistory.org.uk. Retrieved 2020-10-28.
  15. ^ "Acorn Unix Econet Device Driver and Network Device" (PDF). Acorn Computers RISC iX Group. Retrieved 26 November 2014. CS1 maint: discouraged parameter (link)
  16. ^ Athreye, Suma S. (18 July 2000). "Agglomeration and Growth: A Study of the Cambridge Hi-Tech Cluster" (PDF). SIEPR Discussion Paper No. 00-42. Stanford Institute for Economic Policy Research. Archived from the original (PDF) on 13 May 2003. Retrieved 18 June 2012. CS1 maint: discouraged parameter (link)
  17. ^ AUN - Acorn Universal Networking (PDF). Acorn Computers Limited. June 1995. Retrieved 26 November 2014.
  18. ^ Using AUN with the TCP/IP Protocol Suite (Release 2) (PDF) (Technical report). Acorn Computers Limited. 27 May 1994. p. 4. Retrieved 10 March 2021.
  19. ^ TCP/IP Addressing, Subnetworking and Interoperability: an Overview (PDF) (Technical report). Acorn Computers Limited. 11 August 1995. p. 8. Retrieved 10 March 2021.
  20. ^ RISC OS 3 Programmer's Reference Manual. Volume 2. Acorn Computers Ltd. 1992. pp. 2–635. ISBN 1-85250-110-3. |volume= has extra text (help)
  21. ^ a b "RISC OS Programmer's Reference Manual". RISCOS.com. Retrieved 24 November 2014. CS1 maint: discouraged parameter (link)
  22. ^ "RISC OS Programmer's Reference Manual". RISCOS.com. Retrieved 24 November 2014. CS1 maint: discouraged parameter (link)
  23. ^ "Chris's Acorns: Acorn ALA66 Econet podule". chrisacorns.computinghistory.org.uk. Retrieved 2020-10-28.
  24. ^ "6854/68A54/68B54 Advanced Data Link Controller data sheet" (PDF). Motorola. Retrieved 25 November 2014. CS1 maint: discouraged parameter (link)
  25. ^ "Chapter 47 - Econet". RISC OS 3 Programmer's Reference Manual. Volume 2. Acorn Computers Ltd. 1992. pp. 2–609 et seq. ISBN 1-85250-110-3. |volume= has extra text (help)
  26. ^ Murray, Rick. "Econet server software description". Econet Enthusiasts Area. Retrieved 26 November 2014. CS1 maint: discouraged parameter (link)
  27. ^ a b Introducing the Econet® Acorn Computer local area network (PDF). Acorn Computers Limited. February 1983. Retrieved 9 February 2021.
  28. ^ a b c Archimedes Level 4 Fileserver Software (PDF). Acorn Computers Limited. January 1991. Retrieved 7 February 2021.
  29. ^ a b c Filestore (PDF). Acorn Computers Limited. September 1988. Retrieved 7 February 2021.
  30. ^ For example, see articles and mail-order advertisements in Acorn User magazines from the late 1980s onwards.
  31. ^ a b c Connectivity from Acorn (PDF) (1 ed.). Acorn Computers Limited. September 1989. Retrieved 7 February 2021.
  32. ^ a b c d Local Area Networking - Econet (PDF). Acorn Computers Limited (1 ed.). 1986. Retrieved 7 February 2021.
  33. ^ a b "About FileStores". BeebMaster. Retrieved 8 February 2021.
  34. ^ Local Area Networking - Econet (PDF). Acorn Computers Limited (2 ed.). February 1987. Retrieved 7 February 2021.
  35. ^ Connectivity from Acorn (PDF) (2 ed.). Acorn Computers Limited. January 1991. Retrieved 7 February 2021.
  36. ^ Acorn Retail Price List February 1989 (PDF) (9 ed.). Acorn Computers Limited. January 1989. Retrieved 7 February 2021.
  37. ^ Acorn UK Retail Prices October 1991 (PDF) (19 ed.). Acorn Computers Limited. October 1991. Retrieved 7 February 2021.
  38. ^ RISC-iX Group, Acorn Computers, Cambridge, UK. Acorn Unix Econet Device Driver and Network Device (PDF) (Technical report). Acorn Computers Limited. Retrieved 16 October 2020. CS1 maint: discouraged parameter (link) CS1 maint: multiple names: authors list (link)
  39. ^ Econet X25 Gateway (PDF) (1 ed.). Acorn Computers Limited. August 1986. Retrieved 7 February 2021.
  40. ^ The Econet-X25 Gateway (PDF) (Technical report). Acorn Computers Limited. Retrieved 3 April 2021.
  41. ^ Functional Specification of Econet-X25 Gateway (PDF) (Technical report). Acorn Computers Limited. Retrieved 3 April 2021.
  42. ^ Port numbers prior to RISC OS 3.5 are listed at "RISC OS Programmer's Reference Manual". RISCOS.com. Retrieved 26 November 2014. CS1 maint: discouraged parameter (link)
  43. ^ Port numbers for RISC OS 3.5 and later are listed at "RISC OS Programmer's Reference Manual". RISCOS.com. Retrieved 26 November 2014. CS1 maint: discouraged parameter (link)
  44. ^ Port numbers for RISC OS Open are defined in "Hdr.Econet". Econet Enthusiasts Area. Retrieved 26 November 2014. CS1 maint: discouraged parameter (link)

External linksEdit