Industrial Ethernet Basics

What is Ethernet/Industrial Ethernet?

Ethernet is a procedure describing hardware and software for fixed-wire data networks. Ethernet was initially intended for local data networks and thus is also called LAN technology. Ethernet thus enables the exchange of data between all devices connected to a local network in the form of so-called data packets.

Industrial Ethernet is a further development of Ethernet. Here, the object is the application of the Ethernet abilities to devices used in industrial manufacture and control (also called real-time Ethernet). Generally, the devices for control and checking of production processes are integrated into the LAN network of the employee computers which mostly already exist.

Industrial Ethernet – History

The intensive research started more than 10 years ago under the leadership of the IAONA (Industrial Automation Open Networking Alliance). The idea was the use of Ethernet in connection with TCP/IP protocols in order, to create a uniform real-time protocol based on this that can be used for the communication of automation processes. The original Ethernet with a transfer of 10 Mbps was not suitable for this communication, as it was rather collision-prone. This initially led to the development of Fast Ethernet. Here, messages were transferred without collisions by use of switches, message prioritization, and full-duplex transmission. The speed for doing this is 100 Mbps. With this, the ground for the desired fast real-time transfer had been prepared

The Basics

There are approximately 20 different protocols for Industrial Ethernet, which are oriented on IEEE 802.3. With this, fieldbus protocols are transferred via Ethernet by tunneling or encapsulation.

The advantages are the consistency of the communication systems and direct takeover of the application layer of the fieldbus and easy portability.

The disadvantage is the large overheads for using the TCP protocol.

Industrial Ethernet uses the international wiring standards.

The decisive protocol for industrial applications is the CIP protocol. This enables cyclic and time-critical data traffic of the automation technology. CIP networks are interoperable with each other. For example, this enables a DeviceNet to operate with an EtherNet/IP

Real-time Data Transfer

Industrial communication networks are divided into three communication levels:

  1. The routing level: This is found, for example, in automotive manufacturing or in process technology, i.e. in large, highly standardized and automated production installations. Here, the transfer between the individual systems in most cases is not very time-critical. Standard Ethernet (in combination with protocols of information technology) has been used here already for years.
  2. The control level
  3. The actuator/sensor level: with these two levels, the real-time characteristics of the Industrial Ethernet are of special importance.

Aim of the Industrial Ethernet

Industrial Ethernet shall establish a basis-oriented and uniform communication system between the systems of the routing level, the control level, and the sensor level, which enables communication in real-time. In this way, losses from system and transfer errors can be avoided. With this, it is especially important to define an infrastructure valid for all three levels.

Uniform Standard?

Many protocol standards competing with each other have been developed for Industrial Ethernet in the same way as for fieldbuses. Most of these standards based themselves on the fieldbus standards forming the base. However, a common core has formed with Fast Ethernet, which nowadays is being used across the board with all systems.

The developments to real-time Ethernet are supported in the European area (e.g.: EtherCAT, TTEthernet, Ethernet Powerlink, Profinet, and Sercos III) as well as in the USA (e.g.: Open DeviceNet Vendor Association (ODVA), ControlNet International (CI), and the Industrial Ethernet Association (IEA)).

Presently, the most important vendors of Industrial Ethernet are:

Interest group

Ethernet offer

Corresponding fieldbuses

SERCOS international

Sercos III

Sercos II

ODVA

Ethernet/IP

DeviceNet/Control/Net

PI(PNO)

Profinet

Profibus

CLPA

CC-Link IE Field

CC- Link

Modbus IDA

Modbus TCP

Modbus RTU

CiA/ETG/EPSG

EtherCat/ Powerlink

CANopen

Although Industrial Ethernet shows high application rates, the use of fieldbuses is still prevalent. Fieldbuses are suited especially to production processes where cyclic I/O data transfer is important (for example in machine building), while Industrial Ethernet is being used more and more, especially in production processes where performance and clock synchronicity matter.

Advantages over Fieldbuses

  • The transfer of IT data and real-time data takes place at the same time
  • Large network expansions by cascading of switches are possible
  • Transfer of larger data quantities
  • All network participants can access buses at the same time
  • The number of participants is nearly unlimited because of the large address range
  • Different transfer media can be combined (for example cable, radio, light conductors)

Problems

Wiring is consistently based on international wiring standards like ISO/IEC 11801. This forms the wiring structure for all factory and hall networks. The problem is the plug connectors: Initially, Ethernet was developed for non-industrial applications, where RJ45 jacks are mainly used.

However, hitherto unknown interference factors may occur outside the office environment, which may influence the transfer quality and can cause faults in the system. These include:

  • Vibrationen
  • Dirt
  • Humidity
  • Harmful substances

A remedy is offered by the development of new plug connections, for example the RJ45 jack with protection type classification IP67 or the M-jack. This enables, for example, use in heavy industry and in highly sterile rooms.

Industrial Ethernet – Outlook

Research makes steady advances: At present, the focus is on areas such as performance and clock synchronicity. The integration of safety protocols is also being researched extensively. The subject of energy management is also very current.

Industrial Ethernet Basics Part II