The Ethernet Mesh - ISA EXPO 2004

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In early 1970s, Ethernet was developed as a single coaxial cable network. This work led to the original IEEE 802.3 standard in the early 1980s and Ethernet now enjoys being the most popular physical layer LAN technology in use today. Early Ethernet LANs were first wired using coaxial cables, with each station tapping into the cable. As a shared single collision domain (a single cable shared by all devices on the network), this created non-determinism and performance and fault-isolation problems, as well as the lack of network redundancy. To overcome these original Ethernet shortcomings, industrial networks typically deploy multiple networks. This use of multiple networks is hard to deploy and manage, and led to proprietary solutions. As the popularity of Ethernet LANs continued to grow, a more structured approach, called star (or hub-and-spoke) topology, was used where all attaching devices were linked to a repeater. This helped with fault isolation and provided a more organized methodology for expanding LANs, however it did not help with network redundancy. With advent of state-of-the-art standard network technologies, such as Rapid Spanning Tree (IEEE 802.1w), a single Ethernet LAN can now be deployed as a highly reliable, deterministic and self-healing mesh network. The mesh network provides the redundancy needed for industrial networks. It also provides industrial applications with a fault tolerant network with redundant data path failovers in the order of hundreds of milliseconds.

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