Page 2 of 2
Metcalfe and David Boggs, his assistant, published a paper in 1976 describing Ethernet but it developed over a number of years. The first two computers they connected together, at the now famous Xerox Parc laboratory, were called Michelson and Morley after the two physicists that performed an experiment to measure the speed of light through the “luminiferous aether”. Their experiment proved that the “aether” didn’t exist but what else could you call a communication channel that connected Michelson and Morely but “Ethernet”?
Metcalfe left Xerox in 1979 to promote the use of Ethernet as an industry wide standard and to form 3Com, a company making Ethernet hardware. It didn’t take off overnight. For one thing the hardware was expensive. For another there were alternatives such as token ring networks, pioneered by Cambridge University and taken up by IBM as a commercial product. In the early days network hardware was as big as a microcomputer, or rather a small minicomputer, and it took many years before it was made small enough and cheap enough to make it worthwhile to connect microcomputers together.
Metcalfe’s first sketch of how Ethernet might work
Three big companies Digital, Intel and Xerox got together to produce the first standard for Ethernet – sometimes called DIX Ethernet. Today the standards are set by the IEEE and the number that you will hear most often is 802.3 which refers to a set of modern Ethernet standards. The standardisation of the hardware protocols made it possible for a range of manufacturers to enter the market making compatible electronics – or NICs, Network Interface Cards.
A later sketch of a two segment network
An equally big problem as the hardware was the software. There just weren’t any network-based operating systems at the time. Eventually a small company called Novell introduced a network-based operating system that solved the software problem for a while, but that’s another story!
It took quite some time for lower cost peer-to-peer networking operating systems to appear and initially there were a range of non-standard extensions to MS-DOS and then Windows before Microsoft woke up and produced Windows for Workgroups – which more or less standardised the software until the Internet appeared on the scene.
The TCP/IP protocol, the way that the Internet works, is often thought of as the way that all networking works but the truth is rather more complicated.
Small groups of machines are generally connected together using Ethernet hardware and protocols. Every Ethernet network adaptor has a unique numeric address that is allocated by the manufacturer when the card is made - its MAC address.
It is this address that is used to ensure that data packets from one machine get to the intended destination. However the Internet doesn’t work in terms of Ethernet MAC addresses but IP addresses that are derived from the URLs that you type.
Today the main role for Ethernet is to carry TCP/IP packets between machines on a local section of the network.
The way that this works is that the Internet data packet is “wrapped” by the Ethernet data packet which does the real work. Essentially the Internet packet is just the data part of the Ethernet packet! In this sense perhaps it is fair to say that it is the Ethernet that actually drives the majority of the Internet!
Over time the Ethernet specification has developed to take account of new developments. The first big change was the dropping of the thick coaxial cables and the “taps”. In their place was either a network connection based on twisted pair cables or a thinner and cheaper coaxial cable. The original specification became known as 10Base5, the thinner coax system was known as 10Base2 and the twisted pair hardware as 10BaseT.
There are other standards that relate to the use of fibre optic connections but the important changes to the original standards are “speed”! The “10” in the names of the Ethernet standards relates to the transmission speed of 10Mbits/s, which was once thought fast enough for anything. However you have to keep in mind that the sort of information sent over local area networks has changed considerably in the past few years. In particular, where we once just shared files and perhaps sent a little email today we want audio and video links to be carried over the network.
You also have to remember that the 10Mbits/s is the capacity of the cable and this has to be shared, via the Ethernet CSMA/CD protocol, between all of the machines connected.
To meet the demands of a multimedia network the Ethernet specifications were improved to 100Mbits/s and 100Base-T or “Fast Ethernet” was born. This uses a twisted pair cabling and intelligent network hubs to allow older slower Ethernet devices to connect at their own speed. However, even Fast Ethernet isn’t the last word. In 1998 a new Ethernet standard called Gigabit Ethernet was announced. Initially this was a fibre optic standard but a year later 1000Base-T was introduced and this works over four twisted pairs.
If you think 1Gigabit is fast enough the standards committees are have produced standards for 10Gigabit and faster. On another front the growing use of wireless networks takes Ethernet back to where it came from, i.e. to ALOHAnet and ways of sharing the airwaves. Yes wireless LANs make use of the same Ethernet protocol and it’s called 802.11.
The long distance links that make the Internet global may not use Ethernet technology but it provides nearly all of the local connections that we use in one form or another.