How to Deal with Interoperability in the Industrial Environment

Typical Industrial Architectures

A typical architecture of a larger industrial automation system consists of three layers – a layer of sensors and simple devices (e.g. motor starters or electronic overload relays), a controlling layer with PLCs, operator panels or intelligent motor drives, and a layer of information systems.

Each layer has different requirements for the volume of exchange data, speed and determinism. The former approach would address these various requirements by specialised networks, especially in the case of the two bottom layers.

In addition, each larger technology supplier recommended an integration method, according to the supplier’s own preference. As a result, we can encounter many different data networks and protocols in existing industrial applications. The interoperability and scalability of, thus, designed and implemented systems are, and will be for a long time, a nightmare for all system integrators and owners of these solutions.

The situation was unsustainable even before the emergence of Industry 4.0 and IIoT. How to deal with this issue?

Ideally, we wanted to have similar solution that has already existed for information and office systems for years – Ethernet. Ethernet itself has been considered as a standard (actually, a family of standards, as specified below), which is not suitable for the industrial environment due to its characteristics (non-deterministic by definition, not supporting real-time messaging, quite expensive etc.) for long time.

However, factors such as the introduction of new technologies (in particular, intelligent switches), changes in network topology (from tree to star topologies), a full-duplex communication, a higher transmission rates and overall Ethernet technology price reduction over time have made Ethernet an interesting solution to be also used for the communication at the two bottom layers of an industrial automation system as well.

Ethernet, Unmodified Ethernet, EtherNet/IP and Interoperability in the Industrial Environment

Before we talk about the use of Ethernet in industrial applications, we should explain what Ethernet is.

Strictly spoken, Ethernet is defined by standard IEEE 802.3 and represents an implementation of two bottom layers (physical and data link layers) of the Open Systems Interconnection (OSI) model. In industrial practice, metallic twisted pair or fibre optic links are mostly used as the physical medium.

Ethernet in its broader sense is often understood as technology that allows connection to the Internet, including all the protocols of the network and transport layers, especially IP, TCP and UDP protocols. 

The reasons why Ethernet has been increasingly considered in the industrial environment are already indicated above. However, the key shortcomings of Ethernet for industrial automation use, i.e. missing support of real-time data transmission and non-determinism, have not been fully resolved.

Three Solutions

Therefore, solutions were sought to satisfy these needs of industrial applications. Generally, we have three such solutions today. Because of the limited space, we cannot go into much detail, but we can start with saying that only one solution, referred to as “unmodified Ethernet” in literature, is used without any modifications of the Ethernet standard and higher-layer TCP/IP and UDP protocols.

The other two solutions require modifications and extensions of standard protocols or even hardware.

Only standards for data exchange in the industrial environment, that are based on unmodified Ethernet do not require any infrastructure changes (i.e. special switches, routers, etc.), can simply co-exist with other existing protocols and, most importantly, in terms of IIoT, allow smooth integration and interoperability.

One of the few standards fully based on unmodified Ethernet principles is EtherNet/IPTM. EtherNet/IPTM is an open standard managed by ODVA.

We are a founding member of this association and have been benefiting from EtherNet/IPTM on a long-term basis. This technology is also a cornerstone of our solution for full digitalisation of industrial automation called The Connected Enterprise®, which, also thanks to the advantages of EtherNet/IPTM, is an ideal IIoT solution.