What are industrial Ethernet protocols? Explanation of EtherCAT, PROFINET, and EtherNet/IP (Japanese blog) table of contents
Introduction
What is industrial Ethernet?
Basic structure of industrial networks
1. EtherCAT (Ultra-high speed, low latency orientation)
2. Profinet (Flexibility/Interoperability)
3. Ethernet/IP (IT affinity/standardization)
summary
Introduction
Communication in industrial equipment is rapidly shifting from traditional fieldbuses to Ethernet-based systems. At the heart of this shift is the Industrial Ethernet protocol .
This article focuses on three widely used protocols and clearly explains the differences in their technical structure and design philosophy .
EtherCAT
PROFINET
EtherNet/IP
(※Evaluation and implementation methods will be explained in a separate article.)
What is industrial Ethernet ?
In short, industrial Ethernet is a communication technology that enhances "real-time performance," "robustness," and "diagnostic capabilities" compared to general-purpose Ethernet.
Standard Ethernet has the following challenges in industrial applications:
This is a best-effort communication method, and the delay varies depending on the load and switching processes.
Frame loss (packet loss) may occur.
TCP/UDP/IP is not designed for real-time control.
To address these challenges, industrial Ethernet protocols employ unique approaches to achieve the following requirements:
Real-time communication
Synchronization control
Redundant configuration
Diagnostic function
■ Key points for understanding industrial Ethernet: OSI model
One of the key points in understanding industrial Ethernet is the perspective of "at which layer real-time performance is achieved," and the OSI reference model is helpful in understanding this. The OSI model is a framework that divides communication functions into seven layers, and each layer plays a different role, from the transmission of physical signals to application processing.
Industrial Ethernet achieves real-time performance and reliability by using each of the OSI layers as a base and extending and optimizing specific layers for each protocol.
OSI reference model in industrial Ethernet:
hierarchy
name
The role of industrial Ethernet
7
application
Contents of communication data (device control, status, settings)
6
presentation
Data encoding, compression, and encryption
5
session
Establishing, maintaining, and terminating communications
4
transport
Communication quality control (TCP/UDP), data delivery assurance.
3
network
Routing by IP address (determining packet destination)
2
Data Link
Data delivery by MAC address, creation of Ethernet frames
1
physics
Cables (Cat5e/6, etc.), connectors, and physical signal transmission.
Layers used for each industrial Ethernet protocol:
ZHOU_XIAO_0-1779432108374.png
Characteristics of each Ethernet protocol:
protocol
hierarchy
Features
EtherCAT
2
High speed without using IP
PROFINET
RT/IRT is L2 NRT L3/4
Differentiated usage between RT and IRT.
EtherNet/IP
3/4
Standard Ethernet based
These differences in characteristics directly lead to the following:
Speed (real-time performance)
Implementation cost
Applicable use
Basic structure of industrial networks
Industrial Ethernet generally shares a common basic structure regardless of the protocol, and the three protocols discussed in this article (EtherCAT, PROFINET, and EtherNet/IP) are no exception.
■ System and Device Structure
Industrial networks can be broadly divided into the "controller side" and the "device side."
Main device (controller):
It plays a central role in controlling the entire network.
Starting communication and setting connection parameters
Sending output data and receiving input data
Communication management and termination process
Typical examples: PLCs, industrial PCs
Sub-device (device):
Respond to connection requests and send and receive necessary data.
Receiving output data and transmitting input data
Self-notification on the network
Alarms sent as needed
Typical examples: sensors, servos, actuators
■ Communication method: cyclic communication vs. aperiodic communication
Once a connection is established, I/O data is continuously exchanged between the MainDevice and SubDevice at very short intervals. This communication is divided into "periodic communication" and "aperiodic communication" depending on the application.
Cyclic communication (periodic communication)
Application: For real-time control
- Essential for applications requiring real-time performance, such as motor control and I/O control.
Acyclic communication
Uses: Configuration, diagnostics, and event management.
- Used for reading and writing configuration data, diagnostic information, and notifications of unexpected events.
■Key concept supporting real-time performance: Synchronization ( Clock )
In industrial systems, it is extremely important that "all devices operate on the same time standard."
For example, if multiple devices acquire data at different times, Δt₁, Δt₂, and Δt₃, as shown in the diagram below, the information received by the controller (PLC) will not be data from the same time, but rather "separate snapshots" that are staggered in time.
the result:
Occurrence of positional misalignment
Incorrect control judgment
In particular, critical synchronization errors in motion control
This can lead to problems like these.
Therefore, in Industrial Ethernet , a mechanism for synchronizing clocks between devices is a crucial element.
ZHOU_XIAO_2-1779431627985.png
Summary of the technical comparison of the three protocols
EtherCAT
PROFINET
EtherNet/IP
Operating Organization
Bechoff / ETG (EtherCAT Technology Group)
Siemens / PNO (PROFIBUS & PROFINET International)
Rockwell / OVDA (Open Device Net Vendors Association)
Communication method
Summary frame (SubDevice reads and writes data as it passes through the frame)
Layer 2-based real-time communication (RT/IRT)
CIP: Explicit (TCP) / Implicit (UDP) communication model
Main use
Motion control, ultra-high-speed control
General-purpose FA, process control, and a wide range of industrial applications
Factory automation, PLC networks, robots
Cycle time
~31.25μs level (implementation dependent, very fast)
RT: A few milliseconds IRT: 31.25μs (implementation-dependent, TSN/IRT)
Generally, 10ms level (UDP-based)
Synchronization method
Distributed Clock (DC)
IRT: Precision Synchronization (PTCP)
CIP Sync (IEEE1588)
Device Model
PDO / SDO (CANopen over EtherCAT)
Slot / Subslot (GSDML)
Class / Instance / Attribute Object Model
topology
Line, tree, ring (low latency)
Line, Star, Ring (MRP/MRPD)
Line, Star, Ring (DLR)
advantage
In short, high speed and low latency / hardware processing.
Various classes and diagnostic functions, high interoperability
Widely used in standard Ethernet infrastructure, easy to understand.
From here, we will explain the technical characteristics of each.
1. EtherCAT (Ultra-high speed, low latency-oriented)
■ EtherCAT Overview
Developed by Beckhoff Automation, managed by ETG.
It operates at Layer 2 and has no IP/TCP/UDP overhead.
Cycle time: ~ 31.25 μs ( implementation dependent )
Synchronization accuracy: ±1μs or less
ZHOU_XIAO_0-1779258860716.png
■ Network Configuration
Main device (master) and Multiple sub-devices (slaves)
The sub-device is equipped with an ESC ( EtherCAT Slave Controller ) and uses dedicated hardware for high-speed processing.
While a line configuration is the basic setup, it also supports redundant configurations using a ring structure.
ZHOU_XIAO_0-1780967472867.png
Figure: EtherCAT network configuration image
The most distinctive feature of EtherCAT is "on-the-fly processing. " A single frame is processed as it passes through all devices, with each device reading and writing data during transit. Because processing is handled by dedicated hardware (ESC) without involving the CPU, it achieves extremely low latency.
ZHOU_XIAO_3-1780967819685.png
Figure: EtherCAT network transfer image
■ Related protocol conversion: EtherCAT (IEC 61784-2-12)
• CoE (CAN over EtherCAT): Enables CANopen communication to be used by tunneling it over an EtherCAT frame.
• FoE (File over EtherCAT): A protocol for transferring files via EtherCAT.
EoE (Ethernet over EtherCAT): A mechanism for encapsulating and transmitting regular Ethernet frames (such as TCP/IP ).
ZHOU_XIAO_4-1779258860793.png
Figure: EoE protocol conversion by master device (MDevice)
2. PROFINET (Flexibility/Interoperability)
■ PROFINET Overview
Developed by Siemens, managed by PNO.
Standard Ethernet based
Use RT/IRT/NRT depending on the application.
Producer/Consumer Model
■ Network Configuration
Flexible support for various topologies such as line, star, and mixed configurations.
It also supports ring redundancy via MRP ( Media Redundancy Protocol ) / MRPD (IRT) .
PROFINET 's communication performance is classified by " Conformance Class ( CC )".
CC-A : Basic real-time, all IT services (e.g., TCP/IP ) can be used without restrictions.
CC-B : Adds network diagnostics and other features to the general FA 's RT .
CC-C ( IRT 😞 Motion applications in the 31.25 μs class
■ Communication type
NRT: Record Read/Write: Sends and receives parameters and settings aperiodicly. Alarms: Notifies of abnormalities from the device.
RT: Periodic I/O communication, generally 1ms
IRT (Isochronous): Time-synchronized high-speed periodic communication , typically 31.25us.
→ Achieves high flexibility, detailed diagnostics, and high interoperability.
ZHOU_XIAO_5-1779258860863.png
3. EtherNet/IP ( IT compatibility/standardization)
■ EtherNet/IP Overview
EtherNet/IP is managed by ODVA (Open DeviceNet Vendors Association).
It adopts CIP (Common Industrial Protocol), which operates at a layer above TCP/UDP/IP (L3/L4).
Object-Oriented Model
ZHOU_XIAO_6-1779258860900.png
■ Network Configuration
Supports line, star, and ring topologies.
Supports high-speed redundancy using DLR ( Device Level Ring ).
Main device → Scanner : Functions as a controller and typically initiates requests.
Subdevice → Adapter : The device that responds to that request.
■ EtherNet/IP's key feature: "Object-Oriented Model"
Each device is defined as a collection of objects consisting of " Class ," " Instance ," " Attribute ," and " Service ."
Class : Type of function (e.g., Identity , Assembly )
Instance : A specific instance of that class.
Attribute : The specific value that each instance possesses.
Service : Operation details such as reading and writing.
This results in a very clear structure for the device's functions, enabling high compatibility across manufacturers.
ZHOU_XIAO_7-1779258860986.png
■ Communication type
Explicit Messaging Connection
Uses TCP , reads and writes configuration values, performs self-diagnosis, and logs.
Give instructions such as "Read" and "Write" once each.
Implicit Messaging- I/O Connection
Using UDP , it enables real-time communication such as cycle I/O , with the scanner sending and receiving I/O data at regular intervals.
The key feature of EtherNet/IP is its ability to enable high-speed I/O communication using implicit ( UDP ) protocols.
summary
Industrial Ethernet is not just a communication tool; it's a system technology that enables real-time control . The three protocols introduced here each achieve this through a different approach.
protocol
design philosophy
Main uses
EtherCAT
High speed, low latency
Motion control
PROFINET
Flexibility and Integration
General-purpose factory automation (FA)
EtherNet/IP
IT integration
PLC Network
As a future trend, industrial networks will move in the following direction.
TSN ( Time Sensitive Networking )
Security (including CRA compliance)
Integration with OPC UA
In other words, the key lies in the fusion of "real-time × IT integration × security" .
Next time,
Why is the i.MX RT1180 suitable for industrial Ethernet protocols?
Actual implementation and evaluation procedures
We will explain this in detail.
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Communication in industrial equipment is rapidly shifting from traditional fieldbuses to Ethernet-based systems. At the heart of this shift is the Industrial Ethernet protocol .
This article focuses on three widely used protocols and clearly explains the differences in their technical structure and design philosophy .
EtherCAT
PROFINET
EtherNet/IP
(※Evaluation and implementation methods will be explained in a separate article.)
This article will cover the three major protocols that dominate industrial Ethernet: EtherCAT, PROFINET, and EtherNet/IP, and provide a clear explanation of the differences in their technical structures and design philosophies.
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