Ethernet is the worldwide de facto standard for linking computers together.
Ethernet connects hundreds of millions of computers and smart devices across buildings, campuses, cities, and countries. Cables and hard-
ware are widely available and inexpensive (dirt cheap in the case of ordinary office-grade products), and software is written for almost every computing platform.
Ethernet is now a hot topic in automation, where industry-specific networks have dominated: Profibus, DeviceNet, Modbus, Modbus Plus, Remote I/O, Genius I/O, Data Highway Plus, Foundation fieldbus, and numerous serial protocols over the electrical standards of EIA RS-232, RS-422, and RS-485.
In some cases, Ethernet is displacing these networks. In nearly all cases, Ethernet works in demanding installations alongside them.
Ethernet originated at Xerox Palo Alto Research Center in the mid-1970s. The basic philosophy was any station could send a message at any time, and the recipient had to acknowledge successful receipt of the message.
It was successful, and in 1980, the DIX Consortium (Digital Equipment Corp., Intel, and Xerox) formed and issued a specification. The Institute of Electrical and Electronics Engineers (IEEE) took it over and in 1983 issued the Carrier Sense, Multiple Access/Collision Detect (CSMA/CD) specification, their stamp of approval on the technology.
Ethernet has since evolved under IEEE to encompass a variety of standards for copper, fiber, and wireless transmission at multiple data rates.
Ethernet is an excellent transmission medium for data, but by itself falls short of offering a complete solution. A network protocol is also necessary to make it truly useful, and what has evolved alongside of Ethernet is TCP/IP.
From both a historical view as well as in today’s industrial world, the TCP/IP plus Ethernet marriage is a key combination, without which, neither would have survived.
The many formats and nomenclature of Ethernet cabling is a rather unfriendly shorthand terminology. IEEE’s Ethernet naming convention works like this:
• The first number ( 10, 100, 1000) indicates the transmission speed in megabits per second.
• The second term indicates transmission type: BASE = baseband, BROAD = broadband.
• The last number indicates segment length. A 5 means a 500-meter segment length from original Thicknet.
• In the newer standards, IEEE used letters rather than numbers. The T in 10BASE-T means Unshielded Twisted-Pair cables. The T4 in 100BASE-T4 indicates four pairs of Unshielded Twisted-Pair cables. continued
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