Ethernet (IEEE 802.3) is a standard communications protocol used to implement a communication network to enable computers to exchange data with each other. Computers use a Network Interface Card (NIC) to connect to an Ethernet network. This is sometimes called an Ethernet card. Ethernet networks can be wired or wireless.

An Ethernet LAN (Local Area Network) typically uses twisted-pair wires. The most commonly installed Ethernet systems are 10BASE-T (Ethernet), and 100BASE-T (Fast Ethernet), which provide transmission speeds up to 10 Mbps and 100 Mbps respectively. The newest version (Gigabit Ethernet) supports data rates of 1 Gbps (1000 megabits per second).

There are alternatives to using Ethernet to implement a network. Token Ring was one such alternative, as is ATM (Asynchronous Transfer Mode) technology. However, Ethernet is now the most widely implement LAN (Local Access Network) standard for industrial applications.

Ethernet was developed initially developed by Bob Metcalfe, who worked at Xerox Corporation, in 1973. In 1976, the Ethernet was proposed as a standard by Xerox Corporation, DEC (now HP), and Intel. The Ethernet specification served as the basis for the IEEE 802.3 standard. The IEEE (Institute of Electrical and Electronics Engineers) proposed a working group in February (second month) 1980, which accounts for the 802 designation.

Ethernet is commonly used as the backbone for TCP/IP communication. DCOM uses TCP/IP as its data transport layer. Thus, most OPC communication that occurs between computers actually uses Ethernet, and depends on a well-working Ethernet backbone. It is therefore critical to ensure that the Ethernet network infrastructure is working well for OPC to work well.

See also: Hub, Router, Switch, TCP/IP