StarLAN was the first IEEE 802.3 standard forEthernet over twisted pair wiring. It was standardized by theIEEE Standards Association as802.3e in 1986, as the1BASE5 version ofEthernet. The StarLAN Task Force was chaired by Bob Galin.

An early version of StarLAN was developed by Tim Rock and Bill Aranguren atAT&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 astar topology from a centralhub in contrast to thebus network of the shared cable10BASE5 and10BASE2 networks that had been based onALOHAnet.

The standard known as 1BASE5 was adopted as 802.3e in 1986 by members of theIEEE 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 telephoneon-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 calledT568B in the standardTIA/EIA-568 (later calledANSI/TIA-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 respectively) carry the StarLAN signals. This greatly simplified the installation of combined voice and data wiring in countries that usedregistered 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 toprivate branch exchange (PBX) equipment in the event that a StarLAN cable was plugged into the wrong device.

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

Parts of the StarLAN technology were patented by AT&T^[4] and were initially part of a wider vision from AT&T to link theirUNIX-basedAT&T 3B2 minicomputers to a network of MS-DOS PCs.^[5] A StarLAN card was also offered for theAT&T UNIX PC.

In 1988, AT&T released StarLAN 10 operating at 10 Mbit/s. The original StarLAN was renamed StarLAN 1, reflecting its 1 Mbit/s speed.^[6]

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

StarLAN 10 andSynOpticsLattisNet provided the basis for the later 10 megabit per second standard10BASE-T. The 10BASE-T task force was chaired by Pat Thaler,^[8] 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 the3Com 3C-523 could be used with either StarLAN 10 or 10BASE-T, by switching link beat on or off.^[9]

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