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Title: StarLAN  
Author: World Heritage Encyclopedia
Language: English
Subject: Ethernet, Ethernet over twisted pair, Ethernet physical layer, IEEE 802.3, Local area network
Collection: Ethernet
Publisher: World Heritage Encyclopedia


StarLAN was the first IEEE 802.3 standard for Ethernet over twisted pair wiring. It was standardized by the standards association of the Institute of Electrical and Electronics Engineers (IEEE) as 802.3e in 1986, as the 1BASE5 version of Ethernet. The StarLAN Task Force was chaired by Bob Galin.


An early version of StarLAN was developed by by Tim Rock and Bill Aranguren at AT&T Information Systems as an experimental system in 1983.[1] The name StarLAN was coined by the IEEE task force based on the fact that it used a star topology from a central hub in contrast to the bus network of the shared cable 10BASE5 and 10BASE2 networks that had been based on ALOHANET.

The standard known as 1BASE5 was adopted as 802.3e in 1986 by members of the IEEE 802.3 standards committee as the Twisted Pair Medium Access Control sublayer and Physical Signalling sublayer specification in section 12.[2] The original StarLAN ran at a speed of 1 Mbit/s.

A major design goal in StarLAN was reduction in Ethernet installation costs by the reuse of existing telephone on-premises wiring and compatibility with analog and digital telephone signals in the same cable bundle. The signal modulation and wire pairing used by StarLAN were carefully chosen so that they would not affect or be affected by either the analog signal of a normal call, on hook and off hook transients, or the 20 Hz high-voltage analog ring signal. Reuse of existing wires was critical in many buildings where rewiring was cost prohibitive, where running new wire would disturb asbestos within the building infrastructure, and where the bus topology of coaxial bus Ethernet was not installable.

The wire positioning called T568B in the standard TIA/EIA-568 was originally devised for StarLAN, and pair 1 (blue) was left unused to accommodate an analog phone pair. Pairs 2 and 3 (orange and green) carry the StarLAN signals. This greatly simplified the installation of combined voice and data wiring in countries that used registered jack connectors and American wiring practices for their phone service (connecting both to the same cable was a simple matter of using a pin-pin RJ45 splitter or punching down the same wires to two ports). This arrangement prevented harm to private branch exchange (PBX) equipment in the event that a StarLAN cable was plugged into the wrong device.

Since 1BASE5 reused existent wiring, maximum link distance was only approximated at 250 m; depending on cable performance up to 500 m were possible. Up to five chained hubs were allowed.[3]

Parts of the StarLAN technology was patented by AT&T,[4] and initially was part of a wider vision from AT&T, where it would link their UNIX-based AT&T 3B2 minicomputers to a network of MS-DOS PCs.[5]

StarLAN 10

In 1988, AT&T released StarLAN 10, which operated at 10 Mbps. The original StarLAN was renamed to StarLAN 1, reflecting its speed of 1 Mbps. [6]

It was adopted by other networking vendors such as Hewlett-Packard and Ungermann-Bass. Integrated circuits were introduced starting in 1986 that reduced the cost of the interfaces.[7]

StarLAN 10 and SynOptics LattisNet provided the basis for the later 10 megabit per second standard 10BASE-T. The 10BASE-T task force was chaired by Pat Thaler, a member of the StarLAN task force. 10BASE-T used the basic signalling of StarLAN 10 and added link beat. Some network interface cards such as the 3Com 3C-523 could be used with either StarLAN 10 or 10BASE-T, by switching link beat on or off.[8]


  1. ^ Urs von Burg (2001). The triumph of Ethernet: technological communities and the battle for the LAN standard. Stanford University Press. pp. 175–176, 255–256.  
  2. ^ 802.3a,b,c, and e-1988 IEEE Standards for Local Area Networks: Supplements to Carrier Sense Multiple Access With Collision Detection (CSMA/CD) Access Method and Physical Layer Specifications.  
  3. ^ IEEE 802.3 Clause 12.1.4
  4. ^ US 4674085  Patent "Local area network" William L. Aranguren, Mario A. Restrepo, and Michael J. Sidney, Filed October 6, 1986, issued June 16, 1987.
  5. ^ "Although expensive and slow, the system allows minis and PCs to share data" , 27 Oct 1987, p229, PC Mag
  6. ^ StarLAN Technology Report, 4th Edition. Architecture Technology Corporation. 1991. 
  7. ^ Mary Petrosky (June 9, 1986). "Starlan nets: Chip set chips away at Interface cost". Network World 3 (14). p. 4. Retrieved June 10, 2011. 
  8. ^ Ohland, Louis. "3Com 3C523". Walsh Computer Technology. Retrieved 1 April 2015. 
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