11a - Industrial Ethernet overview

Abstract

This chapter provides an insight into the industrial Ethernet systems. The concept of Ethernet network was first developed by Xerox Corporation, using “ether” as the transmission medium and created a network between the sites. Early Ethernet (of the 10 Mbps variety) uses the carrier sense multiple access/collision detect (CSMA/CD) access method. This results in a system that can operate with little delay, if lightly loaded, but access to the medium can become very slow if the network is heavily loaded. Ethernet network interface cards are relatively cheap and produced in vast quantities. Modem Ethernet systems are a far cry from the original design. From 100BASE-T onwards, they are capable of full-duplex (sending and receiving at the same time via switches, without collisions) and the Ethernet frame has been modified to make provision for prioritization and virtual LANs. There are several key technology areas involved in the design of Ethernet-based industrial automation architecture. These include available switching technologies, quality of service (QOS) issues, the integration of existing (legacy) field buses, sensor bus integration, high availability and resiliency, security issues, long-distance communication, and network management. For high availability systems, a single network interface represents a single point of failure (SPOF) that can bring the system down.