The network standard that would eventually become Ethernet had its genesis forty years ago today in a memo between engineers at Xerox. It went on to become so ubiquitous that Ethernet is now synonymous with networking and many people are scarcely aware of any other LAN technology.
Ethernet had a rather protracted birth, with commercial products not shipping until about 1980, but it grew in popularity over the next decade or so until it was the network technology of choice as businesses began to invest in PCs and link them together in order to share resources.
Robert Metcalfe is the engineer credited with inventing Ethernet, first mentioned in a memo circulated to colleagues at Xerox on 22 May, 1973. However, many others had a hand in developing the nascent technology, and the basic concepts behind the technology were actually based on the pioneering Aloha system used to connect users with a central computer at the University of Hawaii.
The latter employed a shared medium to connect all nodes on the network, rather than a dedicated link for each station. Nodes were allowed to transmit packets whenever they had data to send, and resend later if the transmission coincided with another station sending data at the same time, known as a collision.
Early Ethernet implementations adopted a similar approach, sharing a single run of cable and using what is now known as carrier-sensing multiple access with collision detection, or CSMA/CD, to communicate over the line.
It wasn't until Metcalfe had left Xerox that the first commercial products came to market, developed in partnership between Xerox, Intel and Digital Equipment Corporation (DEC). These introduced the 10Mbps Ethernet standard, and typically operated over thick co-axial cable similar to that used for connecting a TV antenna.
The Ethernet specifications were also accepted by the IEEE 802 LAN/MAN Standards Committee and published as the 802.3 standard covering the physical and data link layers for a CSMA/CD network.
Ethernet's subsequent success can partly be attributed to the fact that it wasn't tied to any single vendor, but also because the standard was flexible enough to be adapted to changing requirements. The ability to support twisted-pair cabling dramatically reduced the cost of wiring up a site for Ethernet when it was introduced, for example.
Rival LAN technologies were mostly proprietary, such as Datapoint's ARCnet and Token Ring, which is largely associated with IBM. Token Ring also had the downside that its access method was defined by the topology of the network, making it difficult to add or remove stations from an operating LAN.
Ethernet was also given a boost by being adopted by Novell as the standard way to build a network based around its Novell Netware platform. Netware made it possible to network together a group of PCs with one or more Netware servers providing shared file and print services in the days before Microsoft even had a server version of Windows.
Since the early 1990s, Ethernet has expanded rapidly and pushed out virtually all other network technologies. During this time the line rate has been expanded from 10Mbps to 100Mbps, then 1Gbps, 10Gbps and even 100Gbps inside data centres.
Because of its near ubiquity inside data centres and corporate networks, Ethernet is also now being adopted as the transmission standard for long-distance metropolitan area networks (MANs) or even wide area networks (WANs).
Ethernet has also changed markedly since the early implementations. With the broad adoption of network switches, most connections are point-to-point rather than multiple stations sharing a single multi-drop channel.
The physical layer has also been adapted to use fibre-optic cabling in addition to copper, and several different signal-coding schemes have been introduced to enable reliable transmission at today's very high data rates.
However, Ethernet is still the same old Ethernet at the data link layer, largely maintaining compatibility with the 48-bit addressing and frame format that Ethernet has had since the start. For a forty-year-old technology, that means Ethernet has survived remarkably well in the fast-moving world of IT.
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