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An Ethernet Primer

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Ethernet is the collective name for a group of standards defining local area networks. These standards cover cabling and the structure of data sent over those cables, as well as the hardware that connects the cables. In this article, Kyle Cassidy looks at the fundamentals of this technology and gives you a tour of its components.

Chances are good that the network in your office is running over Ethernet; most today are. But just what is Ethernet? "Ether," of course, is in reference to "luminiferous ether," the mythical substance that people previously believed existed in space through which electricity was carried. Net" is, well, short for "network." You can see that the name is somewhat euphemistic but not unattractive. It suggests that something strange and wonderful is going on, maybe even magical. In truth, there's a lot remarkable about Ethernet but, alas, nothing magical.

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In the 1970s, the fine folks at the Xerox Palo Alto Research Center (PARC) were working hard at inventing the "office of the future," sometimes called the "paperless office." They were visionaries way ahead of their time (and, as a result, no one paid any attention to them and their project died on the vine, only to be resurrected in hindsight by other people who got rich off it). They already had come up with the mouse and the graphical user interface (GUI) similar to the one you're likely using today, and they were looking for a way to network their computers and printers together.

Enter Dr. Robert M. Metcalfe and his brainchild, Ethernet. Metcalfe described a collection of hardware that could carry a network signal and a protocol for computers to use it, including the structure of the blocks of data traveling across the wire. He was successful in networking his computers, but the "office of the future" was a flop. It worked, but it was prohibitively expensive; Xerox shelved the project for 15 years until Apple Computer president Steve Jobs stumbled across it in the 1980s and based the Macintosh Operating System on it.

During that time, however, Xerox hadn't abandoned all of its "office of the future" technologies. The Xerox folks got together with Intel and Digital Equipment Corporation, and together they fussed with the Ethernet design a bit more and published the DIX (Digital, Intel, Xerox) "thick" Ethernet standard in 1980. The companies published a revised standard, DIX 2.0, in 1982. In 1983, the Institute for Electronic and Electrical Engineers published its version of it, called "IEEE 802.3 Carrier Sense Multiple Access with Collision Detection (CSMA/CD) Access Method and Physical Layer Specifications."

The "802.3" in the title is the IEEE working group number that worked to revise and standardize the Ethernet specification. Because of that, the standard sometimes is known as "802.3." (It's also sometimes known as CSMA/CD among the most pedantic sort of computer nerds.) It is useful to know that it's "802.3" only if you're comparing it to the Token Ring standard, 802.5—and, even then, only at the dullest of parties. (If you ever take the MCSE exams, it'll be on there, too. And if you're looking to spit-shine your geek badge of honor, be sure to learn all the 802.3 variants, their release dates, and what kind of impact it had on the computing industry. Those people who love useless trivia will adore you.) In ordinary conversation, you can simply say "Ethernet" or "Token Ring," and everybody will know what you're talking about. The 802.3 standard puts down in writing what happens at the very basest level of network communication: that which actually travels through the wires and hardware.

The IEEE 802.3 standard did not make Ethernet an overnight success, however. In 1985, the IEEE published the 802.3a "thin" Ethernet standard. Since the publication of the 802.3 standard, Ethernet has taken off like a rocket. Today it is the most popular type of LAN. The IEEE 802.3 working group has continually incorporated new features to make Ethernet faster, more affordable, and competitive in today's multimedia-heavy data networks.

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