1255 Industrial Ethernet Protocols

1255.1 Industrial Ethernet: PROFINET, EtherCAT, and TSN

Learning Objectives

By the end of this section, you will be able to:

Compare major industrial Ethernet protocols (PROFINET, EtherNet/IP, EtherCAT)
Understand real-time classes and deterministic networking requirements
Design EtherCAT networks for high-speed motion control
Configure PROFINET for Siemens automation systems
Evaluate Time-Sensitive Networking (TSN) for converged IT/OT
Select appropriate industrial Ethernet for specific applications

1255.2 Prerequisites

Before diving into this chapter, you should be familiar with:

Industrial Protocols Overview: IT/OT networking context
Networking Basics: Ethernet and TCP/IP fundamentals
Wired Communication: Physical layer concepts

Related Chapters

Industrial Protocols: - Industrial Protocols Overview - Protocol landscape - OPC-UA Fundamentals - Integration layer - Modbus Protocol - Legacy comparison

Networking: - Networking Basics - Ethernet fundamentals

For Beginners: Why Industrial Ethernet?

Office Ethernet: Designed for files, emails, web browsing - “Best effort” delivery—packets arrive eventually - A 100ms delay? Nobody notices

Industrial Ethernet: Designed for machine control - Deterministic delivery—packets MUST arrive on time - A 100ms delay? Robot crashes, product ruined

The Challenge: Standard Ethernet wasn’t built for this. When you plug a printer and a robot controller into the same switch, the printer’s large print job can delay the robot’s control packets.

The Solutions: 1. Modified Ethernet (PROFINET IRT, EtherCAT): Change how Ethernet works 2. Priority Mechanisms (TSN): Add strict scheduling to standard Ethernet 3. Dedicated Networks: Keep industrial traffic separate

Real-World Analogy: - Standard Ethernet = Regular highway (everyone shares, traffic jams possible) - Industrial Ethernet = Emergency vehicle lane (guaranteed access for critical traffic)

1255.3 Industrial Ethernet Landscape

Understanding Industrial Ethernet Determinism

Core Concept: Determinism means guaranteed, predictable timing—a control command sent will arrive within a known time window with minimal variation (jitter), regardless of other network traffic.

Why It Matters: Standard Ethernet uses best-effort delivery where packets may be delayed by other traffic. For motion control (robot arms, CNC machines), a delayed command can cause collisions, product defects, or safety hazards. Industrial Ethernet protocols solve this through various mechanisms: time-slotted scheduling (PROFINET IRT), processing-on-the-fly (EtherCAT), or IEEE TSN standards (802.1Qbv time-aware shaper).

Key Takeaway: Match your cycle time requirement to the protocol: <100 microseconds requires EtherCAT or PROFINET IRT; 1-10 milliseconds works with PROFINET RT or EtherNet/IP; >10 milliseconds can use standard Ethernet with OPC-UA or MQTT.

1255.3.2 Protocol Comparison

Protocol	Vendor	Cycle Time	Nodes	Primary Use
PROFINET	Siemens	250μs - 10ms	512	Factory automation
EtherNet/IP	Rockwell	1-10ms	Unlimited	Process, discrete
EtherCAT	Beckhoff	<100μs	65,535	Motion control
CC-Link IE	Mitsubishi	125μs - 10ms	254	Asia-Pacific
POWERLINK	B&R	200μs - 10ms	253	CNC, packaging
SERCOS III	Bosch	31.25μs	511	Motion control

1255.4 PROFINET

1255.4.1 Architecture

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graph TB
    subgraph Classes["PROFINET Classes"]
        NRT[PROFINET NRT<br/>Non-Real-Time<br/>TCP/UDP/IP]
        RT[PROFINET RT<br/>Real-Time<br/>100ms - 10ms]
        IRT[PROFINET IRT<br/>Isochronous Real-Time<br/><1ms]
    end

    NRT --> TCP[Standard TCP/IP<br/>Configuration, diagnostics]
    RT --> ETH[Ethernet Layer 2<br/>Priority tagging]
    IRT --> SYNC[Synchronized<br/>Time slots]

    style NRT fill:#7F8C8D,stroke:#2C3E50,color:#fff
    style RT fill:#E67E22,stroke:#2C3E50,color:#fff
    style IRT fill:#16A085,stroke:#2C3E50,color:#fff

Figure 1255.2: PROFINET performance classes from NRT to IRT

{fig-alt=“PROFINET classes showing three performance tiers: NRT (Non-Real-Time) in gray using standard TCP/UDP/IP for configuration, RT (Real-Time) in orange using Ethernet Layer 2 with priority for 100ms-10ms cycles, IRT (Isochronous Real-Time) in teal using synchronized time slots for sub-1ms cycles.”}

1255.4.2 PROFINET Device Roles

Role	Function	Example
IO Controller	Master device, initiates communication	PLC (S7-1500)
IO Device	Slave device, responds to controller	Remote I/O, drives
IO Supervisor	Configuration and diagnostics	Engineering station

1255.4.3 PROFINET Frame Structure

| Ethernet Header | VLAN Tag | Frame ID | Cyclic Data | Status | FCS |
| 14 bytes        | 4 bytes  | 2 bytes  | Variable    | 4 bytes| 4 bytes|

1255.4.4 Network Topology

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graph TB
    PLC[S7-1500 PLC<br/>IO Controller]

    PLC --> SW1[PROFINET Switch]

    SW1 --> IO1[ET 200SP<br/>Remote I/O]
    SW1 --> IO2[ET 200MP<br/>Remote I/O]
    SW1 --> Drive1[SINAMICS<br/>Drive]
    SW1 --> HMI[HMI Panel]

    IO1 --> M1[Motors]
    IO1 --> S1[Sensors]

    style PLC fill:#16A085,stroke:#2C3E50,color:#fff
    style SW1 fill:#7F8C8D,stroke:#2C3E50,color:#fff
    style IO1 fill:#E67E22,stroke:#2C3E50,color:#fff
    style IO2 fill:#E67E22,stroke:#2C3E50,color:#fff
    style Drive1 fill:#E67E22,stroke:#2C3E50,color:#fff
    style HMI fill:#2C3E50,stroke:#16A085,color:#fff

Figure 1255.3: PROFINET network topology with PLC and IO devices

{fig-alt=“PROFINET network topology showing S7-1500 PLC as IO Controller in teal connecting through PROFINET Switch in gray to IO Devices in orange (ET 200SP, ET 200MP remote I/O, SINAMICS drive) and HMI panel in navy. Remote I/O connects to motors and sensors.”}

1255.5 EtherCAT

1255.5.1 Operating Principle

EtherCAT’s key innovation: Processing on the Fly

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sequenceDiagram
    participant M as Master
    participant S1 as Slave 1
    participant S2 as Slave 2
    participant S3 as Slave 3

    Note over M,S3: Single Frame Travels Through All Slaves

    M->>S1: Ethernet Frame<br/>[All slave data]

    Note over S1: Read relevant bits<br/>Insert output data<br/>Delay: ~1μs

    S1->>S2: Modified Frame

    Note over S2: Read relevant bits<br/>Insert output data<br/>Delay: ~1μs

    S2->>S3: Modified Frame

    Note over S3: Read relevant bits<br/>Insert output data<br/>Delay: ~1μs

    S3-->>M: Return Frame<br/>[Complete I/O data]

    Note over M: All 3 slaves updated<br/>in single network cycle

Figure 1255.4: EtherCAT processing-on-the-fly single frame sequence

{fig-alt=“EtherCAT processing-on-the-fly sequence: Master sends single Ethernet frame containing all slave data, each Slave (1, 2, 3) reads its relevant bits, inserts output data with ~1μs delay, passes frame to next slave. Final slave returns frame to Master. All I/O updated in single network cycle, achieving microsecond-level performance.”}

1255.5.2 EtherCAT Frame Structure

| Ethernet Header | EtherCAT Header | Datagram 1 | Datagram 2 | ... | FCS |
| 14 bytes        | 2 bytes         | Variable   | Variable   |     | 4 bytes|

Datagram Structure:

| Header | Address | Data | WKC |
| 10 bytes| 4 bytes | N bytes | 2 bytes|

WKC (Working Counter): Incremented by each slave that processes the datagram

1255.5.3 EtherCAT Addressing Modes

Mode	Description	Use Case
Position	Sequential order in network	Simple topologies
Node	Configured node address	Large networks
Logical	FMMU-mapped logical address	Process image
Broadcast	All slaves	Configuration

1255.5.4 Distributed Clocks

EtherCAT achieves sub-microsecond synchronization:

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graph LR
    M[Master<br/>Reference Clock] --> S1[Slave 1<br/>DC Slave]
    S1 --> S2[Slave 2<br/>DC Slave]
    S2 --> S3[Slave 3<br/>DC Slave]

    M -.->|Sync Signal| S1
    S1 -.->|Propagated| S2
    S2 -.->|Propagated| S3

    Note1[Jitter < 1μs]

    style M fill:#16A085,stroke:#2C3E50,color:#fff
    style S1 fill:#E67E22,stroke:#2C3E50,color:#fff
    style S2 fill:#E67E22,stroke:#2C3E50,color:#fff
    style S3 fill:#E67E22,stroke:#2C3E50,color:#fff

Figure 1255.5: EtherCAT distributed clocks synchronization chain

{fig-alt=“EtherCAT Distributed Clocks showing Master as reference clock in teal synchronizing DC Slaves (1, 2, 3) in orange through propagated sync signals with jitter less than 1 microsecond. Enables precise synchronized motion control across multiple drives.”}

1255.5.5 EtherCAT Network Topology

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graph TB
    Master[EtherCAT Master<br/>Industrial PC]

    Master --> S1[Slave 1<br/>I/O Terminal]
    S1 --> S2[Slave 2<br/>Servo Drive]
    S2 --> S3[Slave 3<br/>Servo Drive]
    S3 --> S4[Slave 4<br/>I/O Terminal]

    S2 --> Branch1[Branch Slave<br/>EK1100 Coupler]
    Branch1 --> B1[I/O Module]
    Branch1 --> B2[I/O Module]

    S4 -.->|Hot Standby| Master

    style Master fill:#16A085,stroke:#2C3E50,color:#fff
    style S1 fill:#E67E22,stroke:#2C3E50,color:#fff
    style S2 fill:#E67E22,stroke:#2C3E50,color:#fff
    style S3 fill:#E67E22,stroke:#2C3E50,color:#fff
    style S4 fill:#E67E22,stroke:#2C3E50,color:#fff
    style Branch1 fill:#2C3E50,stroke:#16A085,color:#fff

Figure 1255.6: EtherCAT daisy-chain topology with branch support

{fig-alt=“EtherCAT network topology showing Master in teal connected to daisy-chained Slaves (I/O Terminal, Servo Drives) in orange. Branch topology from Slave 2 to EK1100 Coupler with additional I/O modules. Optional hot standby return path from last slave to master for redundancy.”}

1255.6 EtherNet/IP

1255.6.1 Architecture

EtherNet/IP uses the Common Industrial Protocol (CIP) over standard Ethernet:

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graph TB
    subgraph CIP["CIP Application Layer"]
        Objects[CIP Objects<br/>Identity, Assembly, Connection]
        Services[CIP Services<br/>Get Attribute, Set Attribute]
    end

    subgraph Transport["Transport Options"]
        TCP[TCP<br/>Explicit messaging<br/>Port 44818]
        UDP[UDP<br/>Implicit messaging<br/>Port 2222]
    end

    Objects --> Services
    Services --> TCP
    Services --> UDP

    style CIP fill:#16A085,stroke:#2C3E50
    style Transport fill:#E67E22,stroke:#2C3E50

Figure 1255.7: EtherNet/IP CIP protocol architecture stack

{fig-alt=“EtherNet/IP architecture showing CIP Application Layer in teal (CIP Objects for Identity/Assembly/Connection and CIP Services for Get/Set Attribute) with Transport Options in orange (TCP on port 44818 for explicit messaging, UDP on port 2222 for implicit messaging).”}

1255.6.2 CIP Connections

Type	Transport	Use Case
Explicit	TCP	Configuration, diagnostics
Implicit (I/O)	UDP multicast	Cyclic data exchange
Unconnected	UDP	One-time requests

1255.7 Time-Sensitive Networking (TSN)

1255.7.1 TSN Standards

TSN is a set of IEEE 802.1 standards for deterministic Ethernet:

Standard	Name	Function
802.1AS	Timing and Sync	Clock synchronization
802.1Qbv	Time-Aware Shaper	Scheduled traffic
802.1Qbu/802.3br	Frame Preemption	Interrupt low-priority
802.1Qci	Stream Filtering	Ingress policing
802.1CB	Redundancy	Frame replication
802.1Qcc	Configuration	Central management

1255.7.2 TSN Traffic Scheduling

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gantt
    title TSN Time-Aware Shaper (802.1Qbv)
    dateFormat X
    axisFormat %L

    section Critical
    Motion Control    :crit, 0, 100
    Motion Control    :crit, 500, 600
    Motion Control    :crit, 1000, 1100

    section Scheduled
    PLC I/O          :active, 100, 200
    PLC I/O          :active, 600, 700

    section Best Effort
    IT Traffic       :200, 500
    IT Traffic       :700, 1000

Figure 1255.8: TSN time-aware shaper scheduling for three traffic classes

{fig-alt=“TSN Time-Aware Shaper Gantt chart showing three traffic classes over time: Critical motion control traffic in red at fixed intervals (0-100, 500-600, 1000-1100μs), Scheduled PLC I/O in blue between critical slots, Best Effort IT traffic filling remaining windows. Demonstrates deterministic scheduling with guaranteed time slots.”}

1255.7.3 TSN Network Architecture

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graph TB
    subgraph Converged["Converged TSN Network"]
        CNC[CNC Controller]
        TSN1[TSN Switch]
        TSN2[TSN Switch]

        Robot[Robot Controller]
        PLC[PLC]
        Camera[Vision Camera]
        PC[Engineering PC]
    end

    CNC --> TSN1
    TSN1 --> TSN2

    TSN1 --> Robot
    TSN1 --> PLC
    TSN2 --> Camera
    TSN2 --> PC

    subgraph Traffic["Traffic Types"]
        T1[Critical: Motion<br/>1ms cycle]
        T2[Scheduled: I/O<br/>10ms cycle]
        T3[Best Effort: IT<br/>No guarantee]
    end

    style Converged fill:#16A085,stroke:#2C3E50
    style Traffic fill:#E67E22,stroke:#2C3E50

Figure 1255.9: Converged TSN network with mixed traffic types

{fig-alt=“Converged TSN network in teal showing CNC Controller, Robot Controller, PLC (critical devices), Vision Camera, and Engineering PC all connected through TSN Switches. Traffic types box in orange shows three classes: Critical motion (1ms), Scheduled I/O (10ms), Best Effort IT (no guarantee). Single network carries all traffic types with guaranteed timing.”}

1255.7.4 OPC-UA over TSN

The emerging standard for unified industrial communication:

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graph TB
    subgraph App["Application"]
        OPCUA[OPC-UA<br/>Information Model]
    end

    subgraph PubSub["OPC-UA Pub/Sub"]
        Publisher[Publisher]
        Subscriber[Subscriber]
    end

    subgraph TSN["TSN Ethernet"]
        QBV[802.1Qbv<br/>Scheduling]
        AS[802.1AS<br/>Time Sync]
    end

    OPCUA --> PubSub
    Publisher --> TSN
    Subscriber --> TSN

    style App fill:#16A085,stroke:#2C3E50
    style PubSub fill:#E67E22,stroke:#2C3E50
    style TSN fill:#2C3E50,stroke:#16A085

Figure 1255.10: OPC-UA over TSN unified communication stack

{fig-alt=“OPC-UA over TSN stack showing three layers: Application with OPC-UA Information Model in teal, OPC-UA Pub/Sub with Publisher and Subscriber in orange, TSN Ethernet with 802.1Qbv scheduling and 802.1AS time sync in navy. Represents unified industrial communication standard.”}

1255.8 Protocol Selection Guide

1255.8.1 Decision Matrix

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flowchart TB
    Start[Select Industrial Ethernet] --> Q1{Cycle Time?}

    Q1 -->|<100μs| EC[EtherCAT]
    Q1 -->|100μs-1ms| Q2{Vendor?}
    Q1 -->|>1ms| Q3{Integration?}

    Q2 -->|Siemens| PNIRT[PROFINET IRT]
    Q2 -->|B&R| PL[POWERLINK]
    Q2 -->|Open| EC2[EtherCAT]

    Q3 -->|Siemens| PNRT[PROFINET RT]
    Q3 -->|Rockwell| EIP[EtherNet/IP]
    Q3 -->|IT Convergence| TSN[TSN + OPC-UA]

    style Start fill:#16A085,stroke:#2C3E50,color:#fff
    style EC fill:#E67E22,stroke:#2C3E50,color:#fff
    style EC2 fill:#E67E22,stroke:#2C3E50,color:#fff
    style PNIRT fill:#E67E22,stroke:#2C3E50,color:#fff
    style PL fill:#E67E22,stroke:#2C3E50,color:#fff
    style PNRT fill:#2C3E50,stroke:#16A085,color:#fff
    style EIP fill:#2C3E50,stroke:#16A085,color:#fff
    style TSN fill:#16A085,stroke:#2C3E50,color:#fff

Figure 1255.11: Industrial Ethernet protocol selection decision flowchart

{fig-alt=“Industrial Ethernet selection flowchart: Starting with cycle time requirement, sub-100μs leads to EtherCAT, 100μs-1ms branches by vendor (Siemens→PROFINET IRT, B&R→POWERLINK, Open→EtherCAT), greater than 1ms branches by integration need (Siemens→PROFINET RT, Rockwell→EtherNet/IP, IT Convergence→TSN+OPC-UA).”}

1255.8.2 Application Suitability

Application	Best Protocol	Cycle Time	Why
CNC Machining	EtherCAT	100-250μs	Sub-microsecond sync
Robotics	EtherCAT, PROFINET IRT	250μs-1ms	Coordinated motion
Packaging	PROFINET RT, EtherNet/IP	1-10ms	Fast but not critical
Process Control	PROFINET RT, Modbus TCP	10-100ms	Slow processes
Building Automation	BACnet/IP, Modbus TCP	100ms-1s	Non-critical timing

1255.9 Understanding Check

Knowledge Check

Scenario: You’re designing a semiconductor wafer handling system with: - 6-axis robot arm (synchronized 8 axes total) - 50+ I/O points for vacuum, sensors - Vision system for alignment - Integration with MES for recipe management - Requirement: 100μs motion synchronization

Questions:

Which industrial Ethernet would you choose for motion control?
How would you handle the vision system integration?
What about MES connectivity?
How would you ensure 100μs synchronization?

Solution

1. Motion Control: EtherCAT - 100μs requirement eliminates PROFINET RT and EtherNet/IP - EtherCAT achieves 50-100μs cycles easily - Distributed Clocks for sub-microsecond synchronization - Native support in most servo drive manufacturers

2. Vision System Integration: Option A: Separate GigE Vision network (keeps determinism) Option B: EtherCAT with CoE (CAN over EtherCAT) for triggers - Vision processing done off-network - Only trigger/result over EtherCAT (~μs for signal) - Camera images via separate GigE (bulk data)

3. MES Connectivity: OPC-UA via Gateway - EtherCAT master exposes OPC-UA server - MES connects as OPC-UA client - Non-deterministic traffic isolated from motion network - Recipe download before motion, not during

4. Ensuring 100μs Synchronization:

Distributed Clocks Configuration:
- Reference clock: EtherCAT master
- DC slaves: All servo drives
- Propagation delay: Auto-measured at startup
- Sync0 signal: Triggers synchronized motion
- Jitter: <100ns (100× better than requirement)

Network topology:

Master → Drive1 → Drive2 → ... → Drive8 → I/O

Daisy-chain minimizes jitter
Total propagation: 8 × 1μs = 8μs
Plenty of margin for 100μs cycle

Auto-Gradable Quick Check

Which PROFINET communication class is designed for isochronous motion control using scheduled time slots?

PROFINET IRT uses time-aware scheduling (with very low jitter) for synchronized motion control, while RT is deterministic enough for many automation tasks but not isochronous.

EtherCAT achieves high efficiency on standard Ethernet links primarily because devices:

EtherCAT slaves process frames as they pass through (often in hardware), avoiding store-and-forward overhead and allowing one frame to carry data for many devices.

Time-Sensitive Networking (TSN) is best described as:

TSN refers to multiple IEEE 802.1 standards (e.g., time synchronization and traffic shaping/scheduling) that make Ethernet more deterministic.

In an IT/OT convergence design, OPC UA over TSN typically combines:

OPC UA provides the data model and secure communication patterns, while TSN provides time synchronization and scheduled traffic for determinism on Ethernet.

1255.10 Visual Reference Gallery

Explore these AI-generated diagrams that visualize Industrial Ethernet concepts:

Visual: Industrial Ethernet Protocol Comparison

Modern technical diagram comparing Industrial Ethernet protocols including PROFINET, EtherCAT, EtherNet/IP, and TSN showing cycle times, architectures, and use cases in IEEE color palette

Industrial Ethernet protocols

Industrial Ethernet protocols span a range of performance requirements from standard EtherNet/IP to sub-100 microsecond EtherCAT for motion control applications.

Visual: PROFINET Architecture

Geometric diagram showing PROFINET architecture with IO Controller, IO Devices, and communication classes (NRT, RT, IRT) with cycle time guarantees in IEEE color palette

PROFINET network architecture

PROFINET provides a scalable solution from 10ms standard automation to sub-millisecond synchronized motion control using its tiered RT and IRT communication classes.

Visual: EtherCAT Process Data

Artistic visualization of EtherCAT processing-on-the-fly operation showing how frames pass through nodes with each device reading/writing its data inline using flowing design in IEEE color palette

EtherCAT frame processing

EtherCAT achieves exceptional performance through processing-on-the-fly, where each node reads and writes its data as the frame passes through with nanosecond-level precision.

1255.11 Key Takeaways

Summary

PROFINET dominates Siemens ecosystems with RT (10ms) and IRT (<1ms) classes
EtherCAT achieves the fastest cycles (<100μs) with processing on the fly
EtherNet/IP (Rockwell) uses standard TCP/UDP with CIP application layer
TSN is the future—deterministic standard Ethernet enabling IT/OT convergence
Choose by cycle time: <100μs → EtherCAT, <1ms → PROFINET IRT, >1ms → PROFINET RT/EtherNet/IP
Distributed Clocks (EtherCAT) or PTP (TSN) enable sub-microsecond synchronization
OPC-UA over TSN is emerging as the unified industrial standard

1255.12 What’s Next

Continue exploring industrial protocols:

OPC-UA Fundamentals - Integration layer for all protocols
Modbus Protocol - Legacy protocol still in use
Industrial Protocols Overview - Complete landscape