Understanding the concept of Industrial Ethernet

Industrial Ethernet is the term used to describe the use of the Ethernet network protocol in an industrial environment where it is used mostly for automation and process control.  In order to establish an Industrial Ethernet, a number of techniques are used to adapt the Ethernet protocol for the needs of industrial processes.  By making use of non-proprietary protocols such as Industrial Ethernet, automation systems from different manufacturers can be interconnected throughout a process plant.  Industrial Ethernet plays a prominent role in the bigger marketplace dealing with computer interconnections; it reduces cost and improves performance of communications among industrial controllers.  All Industrial Ethernet components utilized in plant process areas are basically designed to work in harsh environments of temperature extremes, humidity, and vibration that exceed the ranges for IT equipment intended to be installed in controlled environments.

Advantages of Industrial Ethernet Protocols

In the past, a PLC (Programmable Logic Controller) was used to communicate with a slave machine using one of a number of possible open or proprietary protocols which includes Profibus, Sinec H1, CANopen, Modbus, DeviceNet, or FOUNDATION Fieldbus.  However, these days there is a growing interest in the use of Industrial Ethernet as the link-layer protocol, with one of the above mentioned protocols as the application layer.

Some advantages of Industrial Ethernet include:

• Increase in distance;
• Increase in speed;
• Increase in overall performance;
• Better interoperability;
• Ability to have more than two nodes on link;
• Ability to use standard optical fiber, cables, hubs, switches, routers, and access points, which are much cheaper than the equivalent serial-port devices; and
• Peer-to-peer architectures replacing master-slave ones.

Difficulties of Industrial Ethernet Protocols

Difficulties of Industrial Ethernet are listed below:

• The migration of existing systems to a new protocol (however, adapters are also available);
• Protocols using TCP may cause real-time uses to suffer;
• Managing a whole TCP/IP stack is more complex than simply receiving serial data; and
• The minimum Fast Ethernet frame size including inter-frame spacing is about 80 bytes.  Typical industrial communication data sizes are closer to 1-8 bytes. This often results in a data transmission efficiency of less than 5%, which subsequently negate any advantages of the higher bit rate.
- On Gigabit Ethernet the minimum frame size is 512Bytes; the typical efficiency is reduced to less than 1%;
- Some Industrial Ethernet protocols introduce modifications to the Ethernet protocol to improve efficiency.