Ethernet is a local area network (LAN) protocol that was originally developed to link computers. Invented by Bob Metcalfe at Xerox Palo Alto Research Center (PARC) and later refined by Xerox, DEC, and Intel, the Ethernet technology specification was later adopted by the IEEE as standard 802.3. The original Ethernet specification called for a bus topology over several media types, including coaxial cable. Today’s common Ethernet implementations use four twisted pairs of copper wires, commonly referred to as Category 5 (Cat-5) or Category 6 (Cat-6) cabling, and provide a raw data transfer rate of 10 or 100 megabits per second (Mbps). A newer Gigabit Ethernet standard, supporting data rates up to 1,000 Mbps, was approved in 1999.
Ethernet is a network that is a very efficient method of transmitting vast amounts of data. Ethernet is ‘open’ – that is, any device can communicate over ethernet if it adheres to an OSI model that defines how ethernet operates. Multiple protocols can be used over the same network – Modbus and Ethernet I/P can work simultaneously over an ethernet network. The defined ethernet packet is the key to ethernet’s flexibility – it is simply a method of transmission and is scalable – speeds have increased as technology has improved. Ethernet can work over copper cables, fiber optics and can also use wireless technology. It is simply the best way to communicate in an industrial environment. Ethernet is a point to point network scheme - ports cannot be divided or daisy chained like RS-485, TX to device / switch A, RX to device / switch B. The TX and RX of an ethernet port, fiber or copper, must both connect to the desired device / switch in the network.