EthernetEthernet
Below is a diagram that Bob Metcalfe drew up in 1976 to describe a new networking technology he and three other gentlemen at Xerox had invented called "Ethernet".
This technology was a watershed in Local Area Networking, and has become the most commonly implemented LAN signaling scheme in use the world over, presently on its third generation, to say nothing of wireless signaling schemes designed around it. But
Ethernet's hegemony was not a guaranteed outcome in 1990, vying with a number of other technologies -- ArcNet, LocalTalk, Token Ring, and, later, FDDI & ATM -- for market supremacy.
As this diagram shows, Ethernet was originally designed as a bus technology, one
where different network hosts share the bandwidth of the cable. Bus technology
LAN signaling schemes "share" the bandwidth, much like people would share a
party line in the early days of telephones, when an individual, switched
telephone connection was costly. Ethernet was conceived as a carrier sense multiple access/collision detection (CSMA/CD) type of
LAN technology. Ironically, this very sharing and collision recovery technology that made
Ethernet compare unfavorably with competing technologies in its early days has
turned out to be a transmission boon in the modern era of switched
transmissions.
Originally, switching technology was very expensive, performed by specialized devices called "bridges", but as this technology decreased in price, it was implemented by manufacturers at the port level (i.e., each device) down to the point where it is presently ubiquitous and inexpensive. In a switched connection, there are only two devices transmitting, just like on a modern switched telephone circuit, there are only two people talking to each other, as opposed to the olden days of party line communications. Consequently the bandwidth previously reserved for collision detection in a shared connection scheme can now be used for higher data throughput on a more "private", switched connection, thereby doubling the data transmission throughput, called duplex transmission. Therefore, although half duplex Ethernet is a CSMA/CD technology, full duplex Ethernet is not.
Another early big advantage of Ethernet was its speed -- 10 megabits/second -- very fast in the early 1980's. And Ethernet built on this historical advantage with the development of 100 megabit transmission Ethernet, wherein all the specifications for Ethernet remained the same, only the rate at which a bit was placed onto the cabling was tenfold increased. This greatly reduced engineering concerns and manufacturing costs, further enhancing Ethernet in the LAN transmission scheme competition. And duplex transmission only furthers this advantage, giving a 10 mb/sec switched connection 20 mb/sec throughput (and 100 mb/sec switched connection 200 mb/sec throughput -- yee haw!)
Ethernet was offered to the world as an open standard by the DIX (DEC/Intel/Xerox) consortium early in networking LAN technology history, 1980. This open system was later codified by the IEEE as an open standard 802.3. The absence of costly licensing fees led to rapid development, helping Ethernet take an early lead in its competition with other LAN transmission schemes.