Where Networks Fit in the IIoT

There has been a raft of articles about networks and their place in the Industrial Internet of Things. Basically, IIoT is at the intersection of IoT and Industrie 4.0. Here’s a 46-second video reminder of how the relate.

There were three articles that caught my attention:

1. Modbus As an IoT Protocol???

John Rinaldi makes the case for Modbus as an IIoT protocol. He begins by rightfully differentiating between end-to-end protocols like Modbus and transport-only, half-way protocols like MQTT. I tried to do the same thing in Is That a Protocol? But John does it better.

However, I cannot imagine designing a new project with Modbus. Modbus is a protocol that I’ve described as “too open” in Open Standards, Proprietary Standards, and in Between:

How can a standard be “too open”? It can be so open that there is no assurance that devices will interoperate. Modbus is a good example here. It just moves bits and bytes that can represent anything you want them to. Many companies adopted their own rules for how the data should be arranged. Remember Enron Modbus? Special IO Servers had to be created to allow the user to modify packets, swap bytes, and other gyrations when unique data arrangements were encountered.

2. What does that “Ready for IIoT” tag really mean? from Balluff’s Sensortech blog.

Shishir Rege presents 5 key characteristics required to be “Ready for IIoT.” In his view IO-Link plays an important role as does OPC UA. No argument from me on these. Although he should have mentioned PROFINET I opine unbiasedly. Read the whole thing for the 5 characteristics.


A niche Industrial Ethernet promoted the fact that all you need for IIoT was them and OPC UA. (Well, they got the OPC UA part right.) This niche Industrial Ethernet has such a small part of the market share pie that they don’t even get their own slice; their buried in “Other.” This is a reminder that the market decides who the winners are.

The Real Answer

To repeat one of my clichéd sayings: “There’s never a substitute for doing the engineering. Use the right network for the right task.” This means IO-Link to sensors, PROFIBUS PA to intrinsically safe areas, PROFINET to controllers, OPC UA to HMI and beyond.

IO-Link. Ok, not really a network; it’s point-to-point wiring with digital communications overlaid. It’s the digital communication part that allows it to fit in the overall architecture. It moves configuration and asset management data back and forth, not just the process value.

PROFIBUS PA. Ideally Industrial Ethernet could land in an intrinsically safe area. Unfortunately, there are no standards for that today. PI is working on that application though in concert with other Industrial Ethernets. In the meantime, PROFIBUS PA can be integrated into PROFINET for the rest of the data’s journey.

PROFINET is the ideal backbone for automation. The market says it’s the winner. High bandwidth, large address space, speed, determinism, diagnostics, redundancy, and more combine to make PROFINET the right choice.

OPC UA is clearly winning the market’s endorsement as the protocol to move data (cum information) to the cloud (and HMIs and historians and…). Too many of the other protocols are transport-only, leaving a lot more engineering to be done to really move the data. OPC UA is part of the RAMI 4.0 model for Industrie 4.0.


All of these networks contribute to IIoT accomplishing its main goal: analytics. These networks provide the data. If you can’t measure it, you can’t analyze it.

–Carl Henning