The I-IoT data flow in the factory

The following diagram depicts the main pieces of equipment, OT devices, networks, and protocols involved in the I-IoT data flow. These are arranged according to their hierarchical structure in the CIM pyramid, as we have already seen in previous chapters:

We will emphasize here that this logical schema is not a complete picture of all of the equipment, devices, networks, and protocols that we have in an industrial plant—nor is it the only possible representation of their interactions and interconnections. As we mentioned in previous chapters, there is no such precise and clear-cut separation of functionalities and devices between CIM levels in the real industrial world. Some devices placed in one particular level can be deployed to an upper or lower level with an enlarged or restricted scope. This is even more true nowadays, with the progress of this technology providing additional capabilities and more computational resources to devices and allowing them to enlarge their initial scope of functionality. Let's take a look at a few examples to understand this better:

• Sensors and actuators: Because these exchange very little information, they are traditionally placed in level 1. Over the past few years, however, smart sensors have been introduced with processing and computing capabilities to exchange and provide much more information.
• PLCs: These are generally placed in level 2. However, we can also have powerful PLCs in level 3, acting as control coordinators and data collectors. We can even have micro PLCs between levels 1 and 2 to control a working cell or to drive a robot or a complex piece of equipment such as a rotating machine.
• SCADA systems: These are located in level 3. We can also have a local Human Machine Interface (HMI) in level 2 to supervise working cells that are cooperating to carry out a specific task locally. SCADA systems have been evolving over the last few years, covering tasks such as tracking, maintenance, and production planning. These are traditionally covered by the MES system in level 4.
• Historians: These are placed in level 3, but we often have a time window snapshot that pushes the time series to a larger replica database that is located in level 4.

Cyber security is not covered in this schema, except for a generic firewall that is placed between the factory and the edge that is exposed to the internet. We will learn how to secure the I-IoT data flow in Chapter 5, Applying Cybersecurity. 

The preceding diagram focuses on the I-IoT data flow. It shows the devices that act as data sources and highlights the network channels and protocols that allow the data and the information to pass along the devices and the layers of the CIM pyramid until they reach the edge and are transferred to the cloud. Let's start by looking at where the digital signals are generated.