Ethernet History

July 17, 2011

We are all used to hearing people talk about wireless communications technology, which has grown to an astonishing degree in a very short time.  There are a significant number of households in the US. for example, that no longer have wired “Plain Old Telephone Service” [POTS], but use cellular phones exclusively.  Similarly, many firms and residences make extensive use of wireless networking technology.  Nonetheless, wired networking technology still forms the backbone for most networks in organizations around the world; the predominant technology used is Ethernet, introduced commercially in the early 1980s, and codified in a collection of standards known as  IEEE 802.3. As computer standards go, one that last more than 30 years is a genuine old-timer; understanding its longevity can shed some light on what makes for a scalable standard.

Ars Technica has a very good feature article that gives an overview of the history of Ethernet; it explains how the basic design principles of Ethernet were adapted to newer circumstances, gaining enormously in network speed in the process.

These days, it is perhaps easy to think that computer networking started with the development of Internet technology in the ARPANet, a project of the Defense Advanced Research Projects Agency.  But in fact, there was a fair amount of networking in use back around 1980, before PCs were introduced.  In our firm, for example, we used electronic mail extensively, as well as systems for database access, shared calendars, and document processing, across geographic locations; other firms had similar facilities.  The problem with these systems was that they were generally proprietary.  Ours was built on IBM’s networking facilities, under the general name of Systems Network Architecture [SNA]; other manufacturers, like Digital Equipment Corp., had their own networking standards.  So the idea of developing a common, standard method of networking computers was itself a significant step.

The introduction of personal computers had the effect of making computing much more accessible to a much larger group of people; but it also meant that there were, within a relatively short time, many more computers that might be connected in a network.   Ethernet was originally developed at Xerox’s Palo Alto Research Center [PARC], and originally ran at a speedy (for the time) 3 Mbps over coaxial cable, used as an electrical transmission line.  It was one of three leading candidates for adoption as a standard; the others were the Token Ring technology, supported by IBM, and Token Bus, backed by General Motors.  Both of these system regulated traffic on the LAN by passing a special message, the “token”, from one station to the next in rotation.  Only the station holding the token was allowed to transmit.  This meant that no confusion could result from everyone talking at once, and that the network’s capacity was deterministic.  Ethernet, in contrast, relies on detecting and resolving such confusion (called “collisions”), rather than on prevention.  In this case, the strategy results in a simpler, cheaper technology which, in practice, works well enough.  (Sometimes an ounce of cure is better than a pound of prevention!)

The original Ethernet (10BASE5) used a bus topology with relatively thick coaxial cable (RG-8X), which was fairly expensive and a pain to work with.  A more practical variant (10BASE2 or Thinnet) was developed using thinner (RG-58) coaxial cable, still in a bus topology.  These systems ran at 10 Mbps, which sounds very slow today, but was blazingly fast compared to data communications with, say, a 1200 baud modem. In the early 1990s, we ran a trading floor network of 100+ workstations and about a dozen servers, broadcasting real-time market data, all on 10 Mbps Ethernet.

Ethernet finally became nearly ubiquitous when technology was developed for running it over unshielded twisted-pair cables [UTP], like those used for telephone wiring.  The 10 Mbps version was called 10BASE-T; it was not long before 100 Mbps speeds were possible, using slightly higher grade UTP cabling technology.  Soon, Ethernet over fibre-optic media was developed, now with the potential to provide 100 Gbps.

But in the end it was Ethernet that won the battle for LAN standardization through a combination of standards body politics and a clever, minimalist—and thus cheap to implement—design. It went on to obliterate the competition by seeking out and assimilating higher bitrate protocols and adding their technological distinctiveness to its own.

In some ways, Ethernet reminds me of the UNIX operating system, whose first release was in 1969, and whose derivatives and descendants are still going strong.  In both cases, the initial designers got some very important things right; Ethernet, for example, omitted complicated collision-prevention logic, and UNIX adopted the “everything is a file” access paradigm.  Though, in both cases, much of the underlying technology has changed dramatically, the original designs provided a sound foundation.

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