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Profinet
Communication protocol
PurposeReal-time Ethernet for industrial Automation
Developer(s)PROFIBUS & PROFINET International
Introduction2003; 22 years ago (2003)
Based onEthernet, Profibus
RFC(s)IEC 61784-2, IEC 61158

Profinet (usually styled as PROFINET, as a portmanteau for Process Field Network) is an industry technical standard for data communication over Industrial Ethernet, designed for collecting data from, and controlling equipment in industrial systems, with a particular strength in delivering data under tight time constraints. The standard is maintained and supported by Profibus & Profinet International [de], an umbrella organization headquartered in Karlsruhe, Germany.

Functionalities

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Overview

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Profinet implements the interfacing to peripherals.[1][2] It defines the communication with field connected peripheral devices. Its basis is a cascading real-time concept. Profinet defines the entire data exchange between controllers (called "IO-Controllers") and the devices (called "IO-Devices"), as well as parameter setting and diagnosis. IO-Controllers are typically a PLC, DCS, or IPC; whereas IO-Devices can be varied: I/O blocks, drives, sensors, or actuators. The Profinet protocol is designed for the fast data exchange between Ethernet-based field devices and follows the provider-consumer model.[1] Field devices in a subordinate Profibus line can be integrated in the Profinet system seamlessly via an IO-Proxy (representative of a subordinate bus system).[3]

Conformance Classes (CC)

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Applications with Profinet can be divided according to the international standard IEC 61784-2 into four conformance classes:

  • Conformance Class B (CC-B) stipulates that the network infrastructure also includes certified products and is structured according to the guidelines of Profinet. Shielded cables increase robustness and switches with management functions facilitate network diagnostics and allow the network topology to be captured as desired for controlling a production line or machine. Process automation requires increased availability, which can be achieved through media and system redundancy. For a device to adhere to Conformance Class B, it must communicate successfully via Profinet, have two ports (integrated switch), and support SNMP.
  • With Conformance Class C (CC-C), positioning systems can be implemented with additional bandwidth reservation and application synchronization. Conformance Class C devices additionally communicate via Profinet IRT.
  • For Conformance Class D (CC-D), Profinet is used via Time-Sensitive Networking (TSN). The same functions can be achieved as with CC-C. In contrast to CC-A and CC-B, the complete communication (cyclic and acyclic) between controller and device takes place on Ethernet layer 2. The Remote Service Interface (RSI) was introduced for this purpose.

Device types

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A Profinet system consists of the following devices:[1]: 3 

  • The IO-Controller, which controls the automation task.
  • The IO-Device, which is a field device, monitored and controlled by an IO-Controller. An IO-Device may consist of several modules and sub-modules.
  • The IO-Supervisor is software typically based on a PC for setting parameters and diagnosing individual IO-Devices.

System structure

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A minimal Profinet IO-System consists of at least one IO-Controller that controls one or more IO-Devices. In addition, one or more IO-Supervisors can optionally be switched on temporarily for the engineering of the IO-Devices if required.

If two IO-Systems are in the same IP network, the IO-Controllers can also share an input signal as shared input, in which they have read access to the same submodule in an IO-Device.[1]: 3 [2] This simplifies the combination of a PLC with a separate safety controller or motion control. Likewise, an entire IO-Device can be shared as a shared device,[1]: 11  in which individual submodules of an IO-Device are assigned to different IO-Controllers.

Each automation device with an Ethernet interface can simultaneously fulfill the functionality of an IO-Controller and an IO-Device. If a controller for a partner controller acts as an IO-Device and simultaneously controls its periphery as an IO-Controller, the tasks between controllers can be coordinated without additional devices.

Relations

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An Application Relation (AR) is established between an IO-Controller and an IO-Device. These ARs are used to define Communication Relations (CR) with different characteristics for the transfer of parameters, cyclic exchange of data and handling of alarms.[1]: 4 

Engineering

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The project engineering[1]: 5  [2] of an IO system is nearly identical to the Profibus in terms of "look and feel":

  • The properties of an IO-Device are described by the device manufacturer in a GSD file (General Station Description). The language used for this is GSDML (GSD Markup Language) - an XML-based language. The GSD file serves an engineering environment as a basis for planning the configuration of a Profinet IO system.
  • All Profinet field devices determine their neighbors.[1]: 8  This means that field devices can be exchanged in the event of a fault without additional tools and prior knowledge. By reading out this information, the plant topology can be displayed graphically for better clarity.
  • The engineering can be supported by tools such as PROFINET Commander[4] or PRONETA.[5]

Dependability

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Profinet is also increasingly being used in critical applications. There is always a risk that the required functions cannot be fulfilled. This risk can be reduced by specific measures as identified by a dependability[6] analyses. The following objectives are in the foreground:

  1. Safety: Ensuring functional safety. The system should go into a safe state in the event of a fault.
  2. Availability: Increasing the availability. In the event of a fault, the system should still be able to perform the minimum required function.
  3. Security: Information security is to ensure the integrity of the system.

These goals can interfere with or complement each other.

Functional safety: Profisafe

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Main article: Profisafe

Profisafe[7] defines how safety-related devices (emergency stop buttons, light grids, overfill prevention devices, ...) communicate with safety controllers via Profinet in such a safe way that they can be used in safety-related automation tasks up to Safety Integrity Level 3 (SIL) according to IEC 61508, Performance Level "e" (PL) according to ISO 13849, or Category 4 according to EN 954-1.

Profisafe implements safe communication via a profile,[8] i.e. via a special format of the user data and a special protocol. It is designed as a separate layer on top of the fieldbus application layer to reduce the probability of data transmission errors. The Profisafe messages use standard fieldbus cables and messages. They do not depend on error detection mechanisms of underlying transmission channels, and thus supports securing of whole communication paths, including backplanes inside controllers or remote I/O.[9] The Profisafe protocol uses error and failure detection mechanisms such as:

and is defined in the IEC 61784-3-3 standard.

Increased availability

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High availability[10] is one of the most important requirements in industrial automation, both in factory and process automation. The availability of an automation system can be increased by adding redundancy for critical elements. A distinction can be made between system and media redundancy.

System redundancy

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System redundancy can also be implemented with Profinet to increase availability. In this case, two IO-Controllers that control the same IO-Device are configured. The active IO-Controller marks its output data as primary. Output data that is not marked is ignored by an IO-Device in a redundant IO-System. In the event of an error, the second IO-Controller can therefore take control of all IO-Devices without interruption by marking its output data as primary. How the two IO-Controllers synchronize their tasks is not defined in Profinet and is implemented differently by the various manufacturers offering redundant control systems.

Media redundancy

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Profinet offers two media redundancy solutions. The Media Redundancy Protocol (MRP) allows the creation of a protocol-independent ring topology with a switching time of less than 50 ms. This is often sufficient for standard real-time communication with Profinet. To switch over the redundancy in the event of an error without time delay, the "Media Redundancy for Planned Duplication" (MRPD) must be used as a seamless media redundancy concept. In the MRPD, the cyclic real-time data is transmitted in both directions in the ring-shaped topology. A time stamp in the data packet allows the receiver to remove the redundant duplicates.

Security

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The IT security concept[11] for Profinet assumes a defense-in-depth[12] approach. In this approach, the production plant is protected against attacks, particularly from outside, by a multi-level perimeter, including firewalls. In addition, further protection is possible within the plant by dividing it into zones using firewalls. In addition, a security component test ensures that the Profinet components are resistant to overload to a defined extent.[13] This concept is supported by organizational measures in the production plant within the framework of a security management system according to ISO 27001.

Application Profiles

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For a smooth interaction of the devices involved in an automation solution, they must correspond in their basic functions and services. Standardization is achieved by "profiles"[14] with binding specifications for functions and services. The possible functions of communication with Profinet are restricted and additional specifications regarding the function of the field device are prescribed. These can be cross-device class properties such as a safety-relevant behavior (Common Application Profiles) or device class specific properties (Specific Application Profiles).[15] A distinction is made between

  • Device profiles for e.g. robots, drives (PROFIdrive), process devices, encoders, pumps
  • Industry Profiles for e.g. laboratory technology or rail vehicles
  • Integration Profiles for the integration of subsystems such as IO-Link systems

Drives

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PROFIdrive[16] is the modular device profile for drive devices. It was jointly developed by manufacturers and users in the 1990s and since then, in conjunction with Profibus and, from version 4.0, also with Profinet, it has covered the entire range from the simplest to the most demanding drive solutions.

Energy

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Another profile is PROFIenergy which includes services for real time monitoring of energy demand. This was requested in 2009 by the AIDA group of German automotive Manufacturers (Audi, BMW, Mercedes-Benz, Porsche and Volkswagen ) who wished to have a standardised way of actively managing energy usage in their plants. High energy devices and sub-systems such as robots, lasers and even paint lines are the target for this profile, which will help reduce a plant's energy costs by intelligently switching the devices into 'sleep' modes to take account of production breaks, both foreseen (e.g. weekends and shut-downs) and unforeseen (e.g. breakdowns).

Process automation

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Modern process devices have their own intelligence and can take over part of the information processing or the overall functionality in automation systems. For integration into a Profinet system,[17][18] a two-wire Ethernet is required in addition to increased availability.

Process devices

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The profile PA Devices [19] defines for different classes of process devices all functions and parameters typically used in process devices for the signal flow from the sensor signal from the process to the pre-processed process value, which is read out to the control system together with a measured value status. The PA Devices profile contains device data sheets for

  1. Pressure and differential pressure
  2. Level, temperature and flow rate
  3. Analog and digital inputs and outputs
  4. Valves and actuators
  5. Analysis equipment

Advanced Physical Layer

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Ethernet Advanced Physical Layer (Ethernet-APL)[20] describes a physical layer for the Ethernet communication technology which is especially developed for the requirements of the process industries. The development of Ethernet-APL was determined by the need for communication at high speeds and over long distances, the supply of power and communications signals via common single, twisted-pair (2-wire) cable as well as protective measures for the safe use within explosion hazardous areas. Ethernet APL opens the possibility for Profinet to be incorporated into process instruments.

Technology

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Profinet protocols

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Profinet uses the following protocols in the different layers[2]: 15  of the OSI model:

OSI-Layer Profinet
7a Application Fieldbus Application Layer (FAL)
Services and protocols 		OPC UA
7b RSI empty empty RPC --
6 Presentation --
5 Session
4 Transport UDP TCP
3 Network IP
2 Data Link TSN CSMA/CD
1 Physical Ethernet

Layers 1-2: Mainly full-duplex with 100 MBit/s electrical (100BASE-TX) or optical (100BASE-FX) according to IEEE 802.3 are recommended[21] as device connections. Autocrossover is mandatory for all connections so that the use of crossover cables can be avoided. From IEEE 802.1Q the VLAN with priority tagging is used. All real-time data are thus given the highest possible priority 6 and are therefore forwarded by a switch with a minimum delay.

The Profinet protocol can be recorded and displayed with any Ethernet analysis tool. Wireshark is capable of decoding Profinet telegrams.

The Link Layer Discovery Protocol (LLDP) has been extended with additional parameters, so that in addition to the detection of neighbors, the propagation time of the signals on the connection lines can be communicated.

Layers 3-6: Either the Remote Service Interface (RSI) protocol or the Remote Procedure Call (RPC) protocol is used for the connection setup and the acyclic services. The RPC protocol is used via User Datagram Protocol (UDP) and Internet Protocol (IP) with the use of IP addresses. The Address Resolution Protocol (ARP) is extended for this purpose with the detection of duplicate IP addresses. The Discovery and basic Configuration Protocol (DCP) is mandatory for the assignment of IP addresses. Optionally, the Dynamic Host Configuration Protocol (DHCP) can also be used for this purpose. No IP addresses are used with the RSI protocol. Thus, IP can be used in the operating system of the field device for other protocols such as OPC Unified Architecture (OPC UA).

Layer 7: Various protocols[1] are defined to access the services of the Fieldbus Application Layer (FAL). The RT (Real-Time) protocol for class A & B applications with cycle times in the range of 1 - 10 ms. The IRT (Isochronous Real-Time) protocol for application class C allows cycle times below 1 ms for drive technology applications. This can also be achieved with the same services via Time-Sensitive Networking (TSN).

Technology of Conformance Classes

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The functionalities of Profinet IO are realized with different technologies and protocols:

Technology of Class A (CC-A)

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The basic function of the Profinet is the cyclic data exchange between the IO-Controller as producer and several IO-Devices as consumers of the output data and the IO-Devices as producers and the IO-Controller as consumer of the input data.[1] Each communication relationship IO data CR between the IO-Controller and an IO-Device defines the number of data and the cycle times.

All Profinet IO-Devices must support device diagnostics and the safe transmission of alarms via the communication relation for alarms Alarm CR.

In addition, device parameters can be read and written with each Profinet device via the acyclic communication relation Record Data CR. The data set for the unique identification of an IO-Device, the Identification and Maintenance Data Set 0 (I&M 0), must be installed by all Profinet IO-Devices. Optionally, further information can be stored in a standardized format as I&M 1-4.

For real-time data (cyclic data and alarms), the Profinet Real-Time (RT) telegrams are transmitted directly via Ethernet. UDP/IP is used for the transmission of acyclic data.

Management of the Application Relations (AR)

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The Application Relation (AR) is established between an IO-Controller and every IO-Device to be controlled. Inside the ARs are defined the required CRs. The Profinet AR life-cycle consists of address resolution, connection establishment, parameterization, process IO data exchange / alarm handling, and termination.

  1. Address resolution: A Profinet IO-Device is identified on the Profinet network by its station name.[note 1] Connection establishment, parameterization and alarm handling are implemented with User Datagram Protocol (UDP), which requires that the device also be assigned an IP address. After identifying the device by its station name, the IO-Controller assigns the pre-configured IP address to the device.
  2. Connection establishment: Connection establishment starts with the IO-Controller sending a connect request to the IO-Device. The connect request establishes an Application Relationship (AR) containing a number of Communication Relationships (CRs) between the IO-Controller and IO-Device.[2] In addition to the AR and CRs, the connect request specifies the modular configuration of the IO-Device, the layout of the process IO data frames, the cyclic rate of IO data exchange and the watchdog. Acknowledgement of the connect request by the IO-Device allows parameterization to follow. From this point forward, both the IO-Device and IO-Controller start exchanging cyclic process I/O data frames. The process I/O data frames don't contain valid data at this point, but they start serving as keep-alive to keep the watchdog from expiring.
  3. Parameterization: The IO-Controller writes parameterization data to each IO-Device sub-module in accordance with the General Station Description Mark-up Language (GSDML) file. Once all sub-modules have been configured, the IO-Controller signals that parameterization has ended. The IO-Device responds by signaling application readiness, which allows process IO data exchange and alarm handling to ensue.[2]
  4. Process IO data exchange / alarm handling: The IO-Device followed by the IO-Controller start to cyclically refresh valid process I/O data. The IO-Controller processes the inputs and controls the outputs of the IO-Device.[2] Alarm notifications are exchanged acyclically between the IO-Controller and IO-Device as events and faults occur.[1]
  5. Termination: The connection between the IO-Device and IO-Controller terminates when the watchdog expires.[2] Watchdog expiry is the result of a failure to refresh cyclic process I/O data by the IO-Controller or the IO-Device.[1] Unless the connection was intentionally terminated at the IO-Controller, the IO-Controller will try to restart the Profinet Application Relation.

Technology of Class B (CC-B)

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In addition to the basic Class A functions, Class B devices must support additional functionalities.[1] These functionalities primarily support the commissioning, operation and maintenance of a Profinet IO system and are intended to increase the availability of the Profinet IO system.

Support of network diagnostics with the Simple Network Management Protocol (SNMP) is mandatory. Likewise, the Link Layer Discovery Protocol (LLDP) for neighborhood detection including the extensions for Profinet must be supported by all Class B devices. This also includes the collection and provision of Ethernet port-related statistics for network maintenance. With these mechanisms, the topology of a Profinet IO network can be read out at any time and the status of the individual connections can be monitored. If the network topology is known, automatic addressing of the nodes can be activated by their position in the topology. This considerably simplifies device replacement during maintenance, since no more settings need to be made.

High availability of the IO system is particularly important for applications in process automation and process engineering. For this reason, special procedures have been defined for Class B devices with the existing relationships and protocols. This allows system redundancy with two IO-Controllers accessing the same IO-Devices simultaneously. In addition, there is a prescribed procedure Dynamic Reconfiguration (DR), how the configuration of an IO-Device can be changed with the help of these redundant relationships without losing control over the IO-Device.

Technology of Class C (CC-C)

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For the functionalities of Conformance Class C (CC-C) the Isochronous Real-Time[1] (IRT) protocol is mainly used.

With the bandwidth reservation, a part of the available transmission bandwidth of 100 MBit/s is reserved exclusively for real-time tasks. A procedure similar to a time multiplexing method is used. The bandwidth is divided into fixed cycle times, which in turn are divided into phases. The red phase is reserved exclusively for class C real-time data, in the orange phase the time-critical messages are transmitted and in the green phase the other Ethernet messages are transparently passed through. To ensure that maximum Ethernet telegrams can still be passed through transparently, the green phase must be at least 125 μs long. Thus, cycle times under 250 μs are not possible in combination with unchanged Ethernet.

In order to achieve shorter cycle times down to 31.25 μs, the Ethernet telegrams of the green phase are optionally broken down into fragments. These short fragments are now transmitted via the green phase. This fragmentation mechanism is transparent to the other participants on the Ethernet and therefore not recognizable.

In order to implement these bus cycles for bandwidth reservation, precise clock synchronization of all participating devices including the switches is required with a maximum deviation of 1 μs. This clock synchronization is implemented with the Precision Time Protocol (PTP) according to the IEEE 1588-2008 (1588 V2) standard. All devices involved in the bandwidth reservation must therefore be in the same time domain.

For position control applications for several axes or for positioning processes according to the PROFIdrive[16] drive profile of application classes 4 - 6, not only must communication be timely, but the actions of the various drives on a Profinet must also be coordinated and synchronized. The clock synchronization of the application program to the bus cycle allows control functions to be implemented that are executed synchronously on distributed devices.

If several Profinet devices are connected in a line (daisy chain), it is possible to further optimise the cyclic data exchange with Dynamic Frame Packing (DFP). For this purpose, the controller puts all output data for all devices into a single IRT frame. At the passing IRT frame, each Device takes out the data intended for the device, i.e. the IRT frame becomes shorter and shorter. For the data from the different devices to the controller, the IRT frame is dynamically assembled. The great efficiency of the DFP lies in the fact that the IRT frame is always only as extensive as necessary and that the data from the controller to the devices can be transmitted in full duplex simultaneously with the data from the devices to the controller.

Technology of Class D (CC-D)

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Class D offers the same services to the user as Class C, with the difference that these services are provided using the mechanisms of Time-Sensitive Networking (TSN) defined by IEEE.

The Remote Service Interface (RSI) is used as a replacement for the Internet protocol suite. Thus, this application class D is implemented independently of IP addresses. The protocol stack will be smaller and independent of future Internet versions (IPv6).

The TSN is not a consistent, self-contained protocol definition, but a collection of different protocols with different characteristics that can be combined almost arbitrarily for each application. For use in industrial automation, a subset is compiled in IEC/IEEE standard 60802 "Joint Profile TSN for Industrial Automation". A subset is used in the Profinet specification version 2.4 for implementing class D.[22]

In this specification, a distinction is made between two applications:

  • isochronous, cyclic data exchange with short, limited latency time (Isochronous Cyclic Real Time) for applications in Motion Control and distributed control technology
  • Cyclic data exchange with limited latency time (Cyclic Real Time) for general automation tasks

For the isochronous data exchange the clocks of the participants must be synchronized. For this purpose, the specifications of the Precision Time Protocol according to IEC 61588 for time synchronization with TSN[23] are adapted accordingly.

The telegrams are arranged in queues according to the priorities provided in the VLAN tag. The Time-Aware Shaper (TAS)[24] now specifies a clock pulse with which the individual queues are processed in a switch. This leads to a time-slot procedure where the isochronous, cyclical data is transmitted with the highest priority, the cyclical data with the second priority before all acyclic data. This reduces the latency time and also the jitter for the cyclic data. If a data telegram with low priority lasts too long, it can be interrupted by a cyclic data telegram with high priority and transmitted further afterwards. This procedure is called Frame Preemption[25] and is mandatory for CC-D.

Implementation of Profinet interface

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For the realization[26] of a Profinet interface as controller or device, no additional hardware requirements are required for Profinet (CC-A and CC-B) that cannot be met by a common Ethernet interface (100BASE-TX or 100BASE-FX). To enable a simpler line topology, the installation of a switch with 2 ports in a device is recommended.

For the realization of class C (CC-C) devices, an extension of the hardware with time synchronization with the Precision Time Protocol (PTP) and the functionalities of bandwidth reservation is required. For class D (CC-D) devices, the hardware must support the required functionalities of Time-Sensitive Networking (TSN) according to IEEE standards.

The method of implementation[27] depends on the design and performance of the device and the expected quantities. The alternatives are

  • Development in-house[28] or with a service provider
  • Use of ready-made building blocks or individual design
  • Execution in fixed design ASIC, reconfigurable in FPGA technology, as plug-in module or as software component.

History

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At the general meeting of the Profibus user organisation in 2000, the first concrete discussions for a successor to Profibus based on Ethernet took place. Just one year later, the first specification of Component Based Automation (CBA) was published and presented at the Hanover Fair. In 2002, the Profinet CBA became part of the international standard IEC 61158 / IEC 61784-1.

A Profinet CBA system [29] consists of different automation components. One component comprises all mechanical, electrical and information technology variables. The component may have been created with the usual programming tools. To describe a component, a Profinet Component Description (PCD) file is created in XML. A planning tool loads these descriptions and allows the logical connections between the individual components to be created to implement a plant.

The basic idea behind Profinet CBA was that in many cases it is possible to divide an entire automation system into autonomously operating - and thus manageable - subsystems. The structure and functionality may well be found in several plants in identical or slightly modified form. Such so-called Profinet components are normally controlled by a manageable number of input signals. Within the component, a control program written by the user executes the required functionality and sends the corresponding output signals to another controller. The communication of a component-based system is planned instead of programmed. Communication with Profinet CBA was suitable for bus cycle times of approx. 50 to 100 ms.

Individual systems show how these concepts can be successfully implemented in the application. However, Profinet CBA does not find the expected acceptance in the market and will no longer be listed in the IEC 61784-1 standard from the 4th edition of 2014.

In 2003 the first specification of Profinet IO (IO = Input Output) was published. The application interface of the Profibus DP (DP = Decentralized Periphery), which was successful on the market, was adopted and supplemented with current protocols from the Internet. In the following year, the extension with isochronous transmission follows, which makes Profinet IO suitable for motion control applications. Profisafe is adapted so that it can also be used via Profinet. With the clear commitment of AIDA[30] to Profinet in 2004, acceptance in the market is given. In 2006 Profinet IO becomes part of the international standard IEC 61158 / IEC 61784-2.

In 2007, according to the neutral count, 1 million Profinet devices have already been installed, in the following year this number doubles to 2 million. By 2019, a total of 26 million[31] devices sold by the various manufacturers are reported.

In 2019, the specification for Profinet was completed with Time-Sensitive Networking (TSN),[32] thus introducing the CC-D conformance class.

Further reading

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Notes

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References

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Revisions and contributorsEdit on WikipediaRead on Wikipedia

Profinet

View on Grokipedia
from Grokipedia
PROFINET is an open Industrial Ethernet standard designed for real-time data exchange in automation systems, connecting controllers such as PLCs and devices like I/O modules and drives.[1] Developed by PROFIBUS & PROFINET International (PI), it builds on Ethernet technology to integrate seamlessly with existing fieldbus systems like PROFIBUS, supporting scalable architectures including line, ring, and star topologies.[1] Key features include three communication channels—TCP/IP for IT integration, Real-Time (RT) for standard automation tasks, and Isochronous Real-Time (IRT) for high-precision motion control—along with advanced diagnostics, safety (PROFIsafe), and energy management capabilities.[1] Introduced in the early 2000s, with the first PROFINET IO specification released in 2003, it complies with international standards such as IEC 61158 and IEEE 802.3.[2] As the leading Industrial Ethernet protocol, PROFINET facilitates faster, safer, and more cost-effective automation across manufacturing and process industries.[3] It supports parallel TCP/IP communication, large configuration limits, and best-in-class diagnostics, enabling seamless integration of devices from multiple vendors.[3] By 2024, over 78.8 million PROFINET nodes had been installed worldwide, with 9.5 million new nodes added that year, surpassing PROFIBUS in total deployment and demonstrating its dominance in modern industrial networking.[4] PI, backed by more than 1,700 member companies globally, continues to advance PROFINET through ongoing specifications, including support for Time-Sensitive Networking (TSN) for enhanced determinism.[5]

Overview and Fundamentals

Definition and Purpose

PROFINET is an open, manufacturer-independent standard for real-time Ethernet communication in industrial automation, developed and maintained by PROFIBUS & PROFINET International (PI).[6] As an innovative Industrial Ethernet solution based on international standards, it enables efficient and standardized data interchange across automation systems.[3] The primary purposes of PROFINET include facilitating seamless data exchange between controllers and field devices, while supporting applications such as distributed input/output (I/O), motion control, and process automation.[6] This allows for integrated operation in diverse industrial environments, from discrete manufacturing to continuous processes, ensuring reliable connectivity without vendor lock-in.[7] PROFINET evolved as the successor to PROFIBUS, transitioning from a serial fieldbus system to Ethernet-based networking to achieve higher data rates—up to 1 Gbit/s—and seamless integration with enterprise IT infrastructures.[7] This shift addresses the limitations of traditional fieldbuses in speed and scalability, positioning PROFINET as a backbone for modern automation.[6] Fundamentally, PROFINET builds on the IEEE 802.3 Ethernet standard, incorporating specialized real-time extensions to deliver deterministic performance critical for time-sensitive industrial tasks.[6]

Key Features and Benefits

PROFINET offers scalability from simple input/output (I/O) applications to complex motion control systems, enabling flexible deployment across diverse automation scenarios.[5] This scalability supports a range of real-time communication levels, from standard TCP/IP for non-time-critical tasks to isochronous real-time (IRT) for high-precision synchronization in motion applications.[8] A core feature is its support for Ethernet speeds up to 1 Gbps, leveraging standard Gigabit Ethernet infrastructure for high-bandwidth data transmission in industrial environments.[9] Plug-and-play integration is facilitated through General Station Description Markup Language (GSDML) files, which are XML-based device descriptions that allow engineering tools to automatically configure devices, supporting multiple product variants and languages for seamless setup.[10][11] Key benefits include reduced cabling costs by reusing standard Ethernet cabling for both IT and industrial communications, eliminating the need for separate fieldbus wiring.[8] Enhanced diagnostics are provided via protocols such as Simple Network Management Protocol (SNMP) for device monitoring and Link Layer Discovery Protocol (LLDP) for automatic topology detection, enabling proactive fault identification and network management.[12] Backward compatibility with PROFIBUS devices is achieved through gateway solutions like pnGate, allowing gradual migration without full system overhauls.[8] Interoperability across multi-vendor environments is ensured by PROFIBUS & PROFINET International (PI)'s mandatory certification process, conducted at accredited test labs, which verifies compliance and plug compatibility for reliable operation. In terms of performance, higher conformance classes achieve cycle times as low as 31.25 µs with jitter below 1 µs, supporting deterministic communication essential for time-sensitive applications like synchronized motion control.[13][14]

System Architecture

Device Types and Roles

In PROFINET networks, devices are classified into specific categories based on their functions within the automation system, enabling structured communication and control. These categories include IO-Controllers, IO-Devices, IO-Supervisors, and integration components such as couplers, gateways, and proxies, which collectively support a hierarchical architecture resembling a master-slave model while adhering to a provider-consumer communication paradigm.[6] The IO-Controller serves as the central management entity, typically implemented as a programmable logic controller (PLC) that executes the automation program. It initiates data exchange by providing output data to configured IO-Devices in its role as a provider and consumes input data from them as a consumer, while also handling configuration, parameterization, and diagnostics for connected devices.[6] This role positions the IO-Controller as the master in the network hierarchy, establishing application relations (ARs) with multiple IO-Devices to orchestrate real-time operations.[6] IO-Devices represent the field-level components, such as sensors, actuators, drives, or distributed I/O modules, that interface directly with the physical process. These devices act as providers of input data (e.g., sensor readings) and consumers of output data (e.g., control commands) from the IO-Controller, supporting both cyclic real-time exchanges and acyclic services for alarms or diagnostics.[6] In the hierarchy, IO-Devices function as slaves, responding to IO-Controller directives without initiating primary control, though they can connect to multiple controllers for shared access in complex setups.[6] IO-Supervisors are engineering-oriented components, such as programming devices (PGs), personal computers (PCs), or human-machine interfaces (HMIs), used for system commissioning, maintenance, and troubleshooting. Unlike IO-Controllers and IO-Devices, they integrate temporarily into the network and do not participate in real-time data exchange, instead focusing on supervisory tasks like device parameterization, status monitoring, and fault analysis.[6] Their role enhances the master-slave dynamic by providing oversight without altering the operational hierarchy.[6] Couplers, gateways, and proxies facilitate interoperability by bridging PROFINET with legacy or external networks, such as PROFIBUS or other fieldbuses. A proxy, for instance, acts as a virtual representative of non-PROFINET devices on the Ethernet network, mapping I/O data, alarms, and diagnostics transparently to enable seamless integration.[15] Couplers and gateways extend this by supporting protocol conversion, allowing a PROFINET IO-Controller to manage remote subnetworks as if they were native IO-Devices, thus maintaining the overall hierarchical structure across heterogeneous systems.[6] The hierarchical roles in PROFINET emphasize a master-slave-like model where IO-Controllers dominate control and configuration, IO-Devices execute field tasks, and IO-Supervisors provide auxiliary support, with couplers/gateways ensuring extensibility without disrupting the core provider-consumer interactions.[6]

Network Structure and Topology

PROFINET networks are organized to leverage standard Ethernet infrastructure while providing industrial-grade reliability and flexibility in layout. The protocol supports a variety of physical topologies, including line, star, tree, and ring configurations, allowing adaptation to diverse plant environments. In a line topology, devices connect sequentially, often using built-in switches for simplicity and reduced cabling. Star and tree topologies facilitate hierarchical structures, centralizing connections through switches to manage proximity-based node groupings efficiently. Ring topologies enhance redundancy, employing protocols such as Media Redundancy Protocol (MRP) or Media Redundancy for Planned Duplication (MRPD) to achieve recovery times in milliseconds or zero downtime through duplicated frames, respectively.[16] At the logical level, PROFINET employs a provider-consumer model to govern cyclic data exchange, where IO controllers act as providers of output data and consumers of input data, while IO devices reverse these roles. This model ensures deterministic communication for real-time applications without requiring custom hardware modifications. Network segmentation is achieved through VLAN tagging per IEEE 802.1Q standards, assigning priority levels (e.g., priority 6 for cyclic data in conformance class A) to isolate traffic types and enhance performance. For expansive setups, subnetting divides large networks into manageable segments, supporting integration across multiple controllers and supervisors while maintaining overall coherence.[6] PROFINET utilizes standard Ethernet cabling, typically Category 5e or higher with 2-pair configurations for 100 Mbps full-duplex operation, enabling segment lengths up to 100 meters over copper (AWG 22) or several kilometers via fiber optics. These cabling options, defined under IEC 61784-5-3, include types A (fixed installation), B (flexible), and C (highly flexible) to suit varying industrial demands. The architecture's scalability accommodates networks with thousands of devices, facilitated by Ethernet's hierarchical switching and PROFINET's support for multiple IO controllers, making it suitable for both small-scale and enterprise-level automation systems.[6][16]

Communication and Engineering

Application Relations and Engineering Tools

In PROFINET systems, Application Relations (ARs) serve as logical channels that establish and manage data transfer between an IO controller and IO devices, encapsulating all communication pathways for reliable exchange during operation. Each AR is initiated by the IO controller during system startup, embedding multiple Communication Relations (CRs) that define specific data flows, such as input/output modules and their parameters. This structure ensures that data exchanges are explicitly specified and secured, supporting both real-time and non-real-time communications without physical wiring dependencies.[17][6] ARs encapsulate multiple types of CRs tailored to different communication needs: I/O data CRs handle cyclic exchanges of process data, such as sensor readings and actuator commands, transmitted at regular intervals to maintain control loop integrity; alarm CRs manage asynchronous notifications for events like device faults or status changes, ensuring timely alerts without disrupting primary data flows; and record data CRs facilitate acyclic communication for on-demand transfers, like diagnostic queries or parameter updates. These CR types collectively enable a modular approach, where an IO controller can maintain multiple ARs with various devices, scaling to complex automation setups. Conformance classes influence AR management by dictating timing and prioritization, though details vary by implementation.[18] The engineering process for PROFINET relies on General Station Description Markup Language (GSDML), an XML-based format that provides comprehensive device descriptions to enable plug-and-play configuration. GSDML files detail a device's identity, modular structure, communication capabilities, process data assignments, and diagnostic options, allowing engineering tools to automatically import and integrate devices into the system topology. During commissioning, engineers import the vendor-supplied GSDML file, which populates the configuration with predefined modules and parameters, minimizing manual setup and ensuring interoperability across certified devices. This standardized description supports parameterization—assigning device-specific values—and diagnostics, such as topology detection and fault localization, streamlining deployment in industrial environments.[10][19] Key engineering tools for PROFINET include Siemens' TIA Portal and STEP 7, which integrate configuration, programming, and diagnostics within a unified interface. TIA Portal facilitates hardware configuration by importing GSDML files, assigning ARs, and generating network setups, while supporting simulation for pre-commissioning testing. STEP 7, embedded in TIA Portal, handles detailed parameterization and online diagnostics, such as monitoring AR status and alarm propagation in real time. Additionally, PI-certified software from various vendors ensures compliance, offering features like device discovery, firmware updates, and performance analysis to maintain system reliability throughout the lifecycle.[20][21]

Integration with Other Systems

Profinet facilitates integration with legacy and alternative industrial networks through specialized gateways and proxy devices, enabling seamless data exchange in heterogeneous environments. Proxies, which function as Profinet IO devices, provide standardized mapping for comprehensive data transfer including I/O, alarms, and diagnostics, distinguishing them from simpler gateways that primarily handle basic I/O data. For instance, Profinet proxies integrate PROFIBUS networks by acting as intermediaries that map PROFIBUS device data into Profinet objects, supporting real-time communication and system redundancy in applications like process automation.[22][15] Similar proxy and gateway solutions extend Profinet compatibility to Modbus TCP/IP and EtherNet/IP protocols. Modbus-to-Profinet gateways enable bidirectional data transfer between Modbus devices and Profinet controllers, often supporting multiple client-server connections for efficient throughput in factory settings. EtherNet/IP integration occurs via dedicated gateways that map EtherNet/IP tags to Profinet IO data, allowing Profinet controllers to interface with Allen-Bradley PLCs and other CIP-based systems without native protocol support. These devices, typically configured as Profinet IO controllers or devices, ensure minimal disruption during migration from fieldbus to Ethernet-based architectures.[23][24] In the realm of IT/OT convergence, Profinet aligns with higher-level standards like OPC UA to bridge operational technology (OT) with information technology (IT) systems, facilitating vertical data flow from field devices to enterprise applications. OPC UA integration into Profinet devices enables the sharing of asset management, diagnostic, and process data with manufacturing execution systems (MES) and enterprise resource planning (ERP) platforms over shared Ethernet infrastructure, standardized via the OPC UA Companion Specification for Profinet. This setup supports edge computing by embedding OPC UA servers in Profinet controllers or external gateways, where edge nodes aggregate and preprocess I/O data locally to reduce latency and bandwidth demands on higher-level networks. Such convergence enhances plant-wide visibility and predictive maintenance without compromising real-time OT performance, often leveraging Time-Sensitive Networking (TSN) to isolate critical traffic.[25][26] Profinet's alignment with Industry 4.0 principles includes compliance with NAMUR recommendation NE 148, which promotes modular plant automation through the Module Type Package (MTP) standard for plug-and-produce interoperability. This enables secure IIoT connections by standardizing module interfaces for data exchange in process industries, with Profinet serving as the underlying Ethernet backbone for MTP-compliant systems to integrate distributed control and supervision across modular skids. Siemens implementations, for example, utilize Profinet with MTP to accelerate digitalization in sustainable process operations, ensuring vendor-neutral automation over the plant lifecycle.[27][28] Recent developments post-2020 have expanded Profinet's reach to sensor-actuator and wireless domains. IO-Link integration maps IO-Link device parameters and process data into Profinet submodules per IEC 61131-9, allowing IO-Link masters to operate as Profinet IO devices for bidirectional communication with sensors and actuators in factory automation. This enhances parameterization and diagnostics at the field level within existing Profinet networks. For wireless extensions, Profinet supports 5G integration via industrial routers that encapsulate Profinet packets over 5G URLLC (Ultra-Reliable Low-Latency Communication), enabling mobile robotics and remote operations with latencies under 1 ms in private 5G deployments. WLAN options, aligned with Wi-Fi 6/7 and TSN, provide complementary non-cellular wireless bridges for less demanding applications, further supporting flexible topologies in Industrie 4.0 environments.[29][30][31]

Conformance Classes

Class A: Real-Time Communication

Profinet Conformance Class A (CC-A) establishes the foundational level of real-time communication within the Profinet ecosystem, leveraging unmodified commercial off-the-shelf Ethernet hardware to enable soft real-time performance suitable for basic industrial automation tasks. This class supports cyclic exchange of input/output (I/O) data with real-time properties, achieving cycle times from 1 ms to 512 ms, which allows for reliable but non-safety-critical operations in environments where precise timing is not paramount. All standard IT services, including full TCP/IP and UDP/IP connectivity, remain unrestricted, facilitating seamless integration with existing office networks.[32][6] At its core, CC-A employs standard Ethernet protocols for communication, using TCP/IP and UDP/IP primarily for non-time-critical data transmission, such as parameterization and general messaging, while real-time cyclic data is handled through optimized Ethernet frames. These real-time frames are prioritized using VLAN tagging in accordance with IEEE 802.1Q, assigning a priority code point (PCP) of 6 to ensure higher precedence over standard traffic in switches that support this mechanism, thereby minimizing delays in shared network environments. Acyclic communication, essential for on-demand data access, operates over UDP/IP or TCP/IP, enabling flexible read/write operations without disrupting the cyclic process data flow.[6][2] Common use cases for CC-A include device configuration during commissioning, where acyclic services assign parameters to I/O devices; diagnostics, supported by a flexible alarm model with three priority levels (maintenance required, urgent maintenance required, and diagnostics) for timely issue detection; and acyclic parameter reading/writing for ongoing monitoring and adjustments. This class is ideal for applications like simple sensor-actuator networks or basic process control, where update rates of 1-100 ms suffice.[32][6] A key limitation of CC-A is its non-deterministic behavior, arising from the shared medium of standard Ethernet, where collisions or competing traffic can introduce jitter and variable latency, as there is no dedicated bandwidth reservation or hardware-level synchronization. Commercial switches compliant with IEEE 802.1D bridging and Link Layer Discovery Protocol (LLDP) are required to maintain basic performance, but advanced network diagnostics or topology detection—features of higher classes—are absent, potentially complicating troubleshooting in larger deployments.[32][6]

Class B: Isochronous Real-Time

Profinet Conformance Class B (CC-B) builds on Class A by adding network management and diagnostics features while maintaining standard real-time (RT) communication for automation tasks. It supports cyclic I/O data exchange with cycle times from 1 ms to 512 ms, suitable for factory and process automation without the need for isochronous precision. This class includes Simple Network Management Protocol (SNMP) support for reading network statistics and topology information, enabling better troubleshooting and monitoring in larger networks.[32][13] The technology underlying Class B relies on real-time (RT) frames identified by the EtherType 0x8892, which bypass the standard TCP/IP stack to prioritize time-critical data delivery. To achieve improved performance, the protocol employs priority queuing in compatible switches to minimize delays from non-real-time traffic. This approach allows for reliable performance over standard Ethernet infrastructure while maintaining low latency for cyclic I/O data and alarms. Hardware requirements remain standard Ethernet components, making it cost-effective for non-motion-control environments.[33][34]

Class C: Enhanced Real-Time

PROFINET Conformance Class C, also known as enhanced real-time or isochronous real-time (IRT), provides hardware-assisted communication for applications requiring sub-millisecond cycle times and precise synchronization. It supports cycle times below 1 ms, with capabilities down to 250 µs, enabling high-speed data exchange while ensuring deterministic behavior through dedicated bandwidth allocation via hardware prioritization. This class builds on the real-time communication of prior classes (A and B) but adds specialized hardware to achieve lower jitter and faster processing, distinguishing it from software-based approaches.[35][13] The technology in Class C utilizes modified Ethernet frames, identified by EtherType 0x8892 for real-time prioritization, combined with time-division multiple access (TDMA) scheduling to reserve bandwidth exclusively for IRT traffic. Low-latency processing is facilitated by dedicated hardware such as field-programmable gate arrays (FPGAs) or application-specific integrated circuits (ASICs) in devices and switches, which handle frame buffering and transmission timing without software intervention. These components ensure that non-IRT traffic is isolated during scheduled timeslots, minimizing interference and supporting jitter values under 1 µs. Isochronous mode incorporates global clock synchronization using the Precision Time Protocol (PTP) defined in IEEE 1588, ensuring a distributed clock reference with jitter below 1 µs to enable synchronized operations like coordinated drive control and axis replacement without disrupting motion processes.[36][37][38] Synchronization in Class C employs an enhanced Precision Time Protocol (PTP) based on IEEE 1588, extended by PROFINET's Precision Transparent Clock Protocol (PTCP), achieving accuracy better than 100 ns across the network. This level of temporal precision is critical for coordinating multiple devices in a distributed system. Certified controllers, devices, and Ethernet switches must support this hardware-timestamped synchronization to maintain alignment.[35][13] Class C is particularly suited for demanding applications such as high-performance motion control, where closed-loop feedback requires exact timing, and robotics, which demand synchronized multi-axis operations for precise path following. These use cases benefit from the class's ability to handle high data rates with minimal variance, ensuring reliable performance in dynamic environments like manufacturing assembly lines.[39][40]

Class D: Time-Sensitive Networking

Profinet Conformance Class D (CC-D), introduced in the Profinet specification version 2.4, integrates Time-Sensitive Networking (TSN) standards from the IEEE 802.1 working group, developed post-2018, to enable ultra-deterministic communication over standard Ethernet infrastructure. This class builds on Ethernet's Layer 2 capabilities to achieve cycle times below 100 µs, such as 31.25 µs, and jitter under 1 µs, depending on network configuration, making it suitable for high-performance automation requiring precise timing. As of May 2025, Class D features are integrated into the PROFINET Planning Guideline, enabling Gigabit Ethernet compatibility for advanced industrial networks.[41][42][43] Key TSN technologies in CC-D include the time-aware shaper (IEEE 802.1Qbv), which schedules traffic transmission windows to prioritize real-time packets and reserve bandwidth, ensuring bounded latency even in mixed IT/OT environments. Frame preemption (IEEE 802.1Qbu) allows urgent real-time frames to interrupt and resume larger non-critical frames, minimizing delays, while redundant streams (IEEE 802.1CB) provide frame replication and elimination for seamless redundancy without single points of failure. These mechanisms facilitate convergence of operational technology (OT) with information technology (IT) traffic, supporting up to 1024 devices in a network.[41][44] The Profinet TSN profile in specification V2.4, released in 2019 and updated through 2021, explicitly supports scheduled traffic for deterministic delivery and seamless redundancy protocols, aligning with Industry 4.0 requirements for flexible, scalable industrial networks. This future-proof approach addresses the need for gigabit Ethernet compatibility and enhanced determinism in smart manufacturing, enabling broader adoption of converged networks without proprietary hardware.[45][41][13]

Protocols and Technology

Core Profinet Protocols

PROFINET operates on a protocol stack built upon standard Ethernet II (IEEE 802.3), incorporating PROFINET-specific layers to enable industrial automation communication while leveraging IT standards such as TCP/IP and UDP for interoperability.[6] The stack supports both cyclic and acyclic data exchange, with real-time capabilities achieved through dedicated frame formats that bypass higher-layer overhead for deterministic performance.[6] This layered approach ensures seamless integration with existing Ethernet infrastructure, allowing cycle times as low as 250 μs for time-critical applications.[6] A foundational element is the Discovery and Configuration Protocol (DCP), also known as Discovery and Basic Configuration Protocol, an Ethernet link-layer protocol (EtherType 0x8892) that operates primarily within a single subnet, used for device identification, naming, and address assignment without relying on traditional IP protocols like DHCP to prevent conflicts in mixed networks.[46] DCP operates via multicast and unicast services, including "Identify" to discover devices by name or broadcast, "Get" to retrieve configuration details such as IP address and MAC, and "Set" to assign symbolic names (e.g., "device.example.com") and IP addresses dynamically during startup or reconfiguration.[46] This mechanism supports automated assignment by the PROFINET I/O controller; for example, on Cisco Industrial Ethernet switches (such as the Catalyst IE3x00, IE31xx, and IE9300 series), the controller automatically detects the switch and assigns the device name (referred to as PROFINET ID) and IP address via DCP, enabling basic setup without manual intervention. Manual assignment is also possible using Cisco IOS commands (e.g., profinet id <name>) or tools like STEP7/TIA Portal. This IP-based addressing ties the device's unique MAC address (often using the PI Organizationally Unique Identifier 00-0E-CF) to its operational identity, enabling plug-and-play topology discovery while avoiding DHCP overlaps by prioritizing PROFINET-specific assignment.[6][46] For real-time cyclic communication, PROFINET employs the Real-Time (RT) protocol, utilizing unacknowledged "IO Data CR" frames with EtherType 0x8892 to transmit process data between controllers and devices at fixed intervals, typically ranging from 1 ms to 512 ms depending on conformance class.[6] This protocol prioritizes low-latency delivery by handling frames at Layer 2, with optional provider/contract mechanisms to schedule traffic and ensure jitter below 1 ms in standard setups.[6] Network management integrates the Simple Network Management Protocol (SNMP) over UDP (port 161), which is mandatory for conformance classes B and C, allowing controllers to monitor device status, topology via LLDP extensions, and performance metrics through standardized Management Information Bases (MIBs).[6] SNMP facilitates diagnostics like trap notifications for alarms, ensuring reliable operation without disrupting real-time channels.[12] Acyclic communication in PROFINET supports non-time-critical data exchanges, such as parameterization or diagnostics, through Get and Put services implemented via UDP or TCP.[47] These services use "Record Data CR" frames to read (Get) or write (Put) data records addressed by slot, subslot, and index identifiers, enabling access to manufacturer-specific or system-defined parameters without interrupting cyclic traffic.[6] For instance, a controller can issue a Get request to retrieve diagnostic data from a remote device, with responses encapsulated in UDP datagrams to minimize overhead in high-volume scenarios.[47] This approach balances flexibility with the protocol's real-time priorities, often referencing conformance classes for varying levels of support.[6]

Interface Implementation Details

Profinet interfaces are implemented in devices through a combination of hardware accelerators and software layers to ensure real-time performance and interoperability. Hardware implementations often rely on application-specific integrated circuits (ASICs) or field-programmable gate arrays (FPGAs) to handle the demands of real-time (RT) and isochronous real-time (IRT) communication. Siemens' ERTEC family of ASICs, such as the ERTEC 200P series, provides integrated support for Profinet RT frames by incorporating an ARM-based processor, Ethernet MAC, and a switch for multi-port devices, enabling cycle times as low as 125 μs without external components.[48][49] These ASICs process RT telegrams with low latency, offloading the host CPU and supporting features like scheduled IRT traffic through dedicated hardware queues. FPGA-based implementations offer flexibility for custom Profinet devices, particularly in safety-critical applications. For instance, Softing's PROFINET Device Subsystem for Altera-Intel FPGAs integrates a real-time Ethernet controller with an industrial switch IP core, allowing seamless embedding into programmable logic for RT/IRT operations.[50] Similarly, implementations on Xilinx SoC FPGAs have been used to realize RT switches by handling protocol functionality in hardware, minimizing software overhead for high-precision timing.[51] These FPGA solutions are pre-certified to Profinet standards, reducing development time while supporting conformance to classes up to IRT. Post-2020 advancements in chip technology have enhanced Profinet interface performance, with Siemens releasing the ERTEC 200P-3 ASIC in 2023 and firmware updates to version 5.3 in 2025, incorporating optimizations for dynamic reconfiguration and security features like PROFIsec.[52] These updates address evolving requirements for higher throughput and integration with Time-Sensitive Networking (TSN), ensuring backward compatibility with legacy ERTEC devices. Software stacks form the upper layers of Profinet interfaces, abstracting hardware for application integration. The open-source PROFINET Community Stack, maintained by PROFIBUS & PROFINET International (PI), provides full controller and device functionality with APIs for porting to various operating systems and hardware platforms, including Linux-based interfaces.[53] Siemens offers a PROFINET stack in source code, bundled with the eCos real-time operating system and development tools for ERTEC ASICs, facilitating RT/IRT implementation on embedded systems.[54] Compliance testing for these stacks is conducted using PI's ART tester tool, which verifies adherence to Profinet specifications through automated conformance checks against sample applications.[55] Diagnostics in Profinet interfaces enable rapid fault detection and maintenance. LED indicators on device ports, such as those in Siemens SIMATIC ET 200 systems, signal link status, speed, and errors like port interchanges or disabled states using bicolor lights for quick visual assessment.[56] Integrated web servers provide detailed diagnostics, allowing access to device parameters, alarm logs, and configuration via a browser by entering the device's IP address, as implemented in modules like SEW-Eurodrive's DFS21B and ABB's FPNO-21.[57][58] For drive applications, PROFIdrive extends diagnostics through standardized parameter access and fault messaging, defined in IEC 61800-7, enabling controller-device interoperability for status monitoring and error handling.[59] Certification ensures Profinet interfaces meet interoperability standards through rigorous type testing. PI-accredited Test Laboratories (PITLs) perform mandatory conformance tests on devices and stacks, validating protocol compliance, real-time performance, and integration across vendors using tools like the PROFINET Tester, which has been refined since its 2015 debut to cover TSN extensions.[60][37] This process, including pre-certification options for stacks like the Community Stack, guarantees seamless operation in multi-vendor environments.[61]

Application Profiles

Drive Technology

The PROFIdrive profile serves as a vendor-independent specification for integrating variable frequency drives (VFDs), motors, and encoders into Profinet networks, providing standardized parameterization and data exchange to ensure interoperability across manufacturers. Defined in IEC 61800-7, it extends Profinet's capabilities for drive control by supporting functions analogous to those in legacy protocols like SERCOS, but optimized for Ethernet transmission, including cyclic and acyclic communication for process data and diagnostics.[59][62][63] Central features of PROFIdrive in Profinet include isochronous mode, which synchronizes multiple drive axes with jitter-free timing down to 31.25 μs cycles, relying on Profinet's Class B and Class C conformance for enhanced real-time performance. Encoder interfaces enable direct connection for position feedback in closed-loop systems, while safety-integrated drives incorporate PROFIsafe mechanisms for functional safety up to SIL 3/PLe without separate wiring. These elements facilitate precise motion control in dynamic environments.[63][59][64] By consolidating control signals, status information, and sensor data onto a single Ethernet cable, PROFIdrive significantly reduces wiring complexity compared to traditional fieldbus setups, minimizing installation costs and space requirements. Commissioning is accelerated through uniform parameter sets and integrated diagnostics, allowing quick configuration and testing of drive systems. In practice, PROFIdrive enables seamless integration in high-precision applications such as robotics for coordinated multi-axis movements and CNC machines for interpolated path control.[63][65][66]

Energy Management

The PROFIenergy profile serves as a standardized application layer for Profinet, facilitating the exchange of energy-related data between control devices, such as programmable logic controllers (PLCs), and energy-consuming units (ECUs) like drives, actuators, and robots.[67] It enables centralized commands for device states, including startup, shutdown, and standby modes, to optimize power usage during production pauses, such as lunch breaks or holidays, without requiring external hardware.[68] These commands operate through a state model that coordinates firmware agents in ECUs, ensuring safe transitions to low-power modes while maintaining network connectivity for quick reactivation via mechanisms like Wake on LAN.[67] Key features of PROFIenergy include the measurement and reporting of active and reactive power, voltage, current, frequency, and power factor, all integrated into Profinet IO-Device modules for real-time monitoring.[68] Energy consumption is tracked through counters that accumulate data over time, allowing controllers to receive feedback for visualization, peak load shedding, and adaptive energy reduction during unscheduled downtimes.[67] This metering adheres to IEC 61557-12 standards, providing interoperable interfaces that support both short-term standby (up to one hour) and extended deep-sleep modes for longer pauses.[68] In smart factories, PROFIenergy enables load management by dynamically adjusting power draw across networked devices, reducing overall energy costs and supporting compliance with ISO 50001 energy management systems through systematic data collection and efficiency audits.[68] For instance, factories can use it to shift non-essential loads during high-demand periods, minimizing grid strain and carbon emissions while meeting regulatory requirements like EN 17267 for energy transparency.[67] Recent developments since 2021 have integrated PROFIenergy with Industrial IoT platforms via OPC UA (Part 30141), allowing energy data to feed into cloud-based analytics for predictive maintenance, such as detecting anomalies in power consumption patterns that signal impending equipment failures.[68] This IT-OT convergence enhances proactive strategies, extending asset life and further aligning with ISO 50001 goals for continuous improvement.[69]

Process Automation

Profinet adaptations for process automation address the needs of continuous and batch processes in industries such as chemicals, pharmaceuticals, and oil and gas, where reliable communication with field devices is essential for monitoring and control. These adaptations emphasize integration with legacy systems, enhanced safety in hazardous environments, and seamless data exchange for devices like sensors, actuators, and controllers. By leveraging Ethernet-based communication, Profinet enables higher data throughput and diagnostics compared to traditional fieldbuses, facilitating the transition to digital architectures while maintaining compatibility with established protocols.[70] PROFIsafe extends functional safety to process field devices, including valves, pressure and temperature transmitters, enabling safe operation up to Safety Integrity Level 3 (SIL 3) as defined by IEC 61508. This safety layer operates over standard Profinet infrastructure, allowing black-channel communication where safety is handled at the application layer without requiring specialized hardware modifications to the network. For devices with HART integration, Profinet supports proxy gateways that encapsulate HART commands within Ethernet frames, preserving analog signal overlays for hybrid setups and enabling seamless migration from HART-based systems to full digital communication. These features ensure that safety-relevant data, such as emergency shutdown signals for valves, is transmitted reliably in process environments.[71][70][72] The Advanced Physical Layer (APL), based on the 10BASE-T1L single-pair Ethernet standard, provides intrinsic safety for hazardous areas classified under ATEX and IECEx zones, complying with IEC 61158-2020 for fieldbus physical layer specifications. APL supports full-duplex communication at 10 Mbit/s over two-wire cabling, with power delivery up to 60 W per port via 2-Wire Intrinsically Safe Ethernet (2WISE) per IEC TS 60079-47, eliminating the need for separate power lines. This enables long-distance cabling up to 1000 m in trunk segments, ideal for sprawling process plants, while spurs can extend up to 200 m to field devices, bridging gaps in legacy installations without explosion-proof enclosures.[73][74][75] The PA Profile 4.0 standardizes Profinet device behavior for process automation, facilitating migration from fieldbuses like PROFIBUS PA and FOUNDATION Fieldbus through defined interoperability parameters. It incorporates NAMUR NE 131 core elements for device description and NAMUR NE 107 for standardized diagnostics, ensuring consistent status messaging for sensors such as level and flow transmitters. This profile supports automatic device replacement and plug-and-produce functionality, reducing commissioning time in batch processes by aligning manufacturer-independent parameters for alarms, maintenance, and process variables.[76][70][77] As of October 2025, certification is available for all device types using Profinet over APL, with ongoing field tests demonstrating positive results in process industry applications.[78][79]

Dependability and Security

Functional Safety with Profisafe

PROFIsafe is the established open safety communication profile integrated into PROFINET, enabling the transmission of safety-related data over standard, non-safety-rated Ethernet networks without requiring dedicated safety infrastructure.[80] It operates on the black-channel principle, treating the underlying communication channel—such as copper, fiber optic, or wireless—as opaque and untrusted, while ensuring safety through protocol-level measures independent of the physical medium.[80] This approach allows safety and standard data to share the same network, simplifying system architecture in industrial automation.[81] Certified to Safety Integrity Level 3 (SIL 3) per IEC 61508, PROFIsafe supports applications requiring high functional safety, including up to Performance Level e (PL e) and Category 4 as defined in ISO 13849-1.[81] The protocol embeds safety functions directly into PROFINET frames, using dedicated safety Application Relation (AR) identifiers to distinguish fail-safe data exchanges from standard communications.[80] Key mechanisms include cyclic redundancy checks (CRC) for detecting data corruption or manipulation, timestamps to monitor transmission delays and ensure timely delivery, and unique source/destination addressing (F-Source and F-Destination) to prevent unauthorized or misrouted safety messages.[81] These elements collectively provide robust protection against common failures like message loss, repetition, or insertion, achieving the required diagnostic coverage for SIL 3 without modifying the base Ethernet hardware.[80] Integration of PROFIsafe occurs within IO-Devices configured as F-Devices (fail-safe devices), where safety logic is implemented via certified hardware and software modules, often using device description files like F-GSD for parameterization.[80] In practice, PROFIsafe facilitates critical applications such as emergency stop functions (E-Stops) for immediate hazard mitigation and safe motion control in drive systems, ensuring controlled deceleration or shutdown in response to safety events.[80] These capabilities have led to widespread adoption, with over 28.7 million nodes installed worldwide as of 2024, in discrete manufacturing and process industries.[80][82]

Availability and Redundancy Mechanisms

Profinet ensures high availability in industrial automation environments through a suite of redundancy mechanisms designed to minimize downtime and maintain continuous operation during faults such as device failures, link breaks, or controller malfunctions. These mechanisms operate at different layers, from individual devices to the overall network topology, providing fault-tolerant configurations that support seamless recovery without interrupting real-time data exchange. By integrating standardized protocols, Profinet achieves recovery times ranging from milliseconds to zero-switchover, making it suitable for mission-critical applications in manufacturing and process control.[83] System redundancy in Profinet focuses on duplicating key components to enable automatic failover, particularly at the device and controller levels. Device-level redundancy allows for backups where a secondary device mirrors the primary, enabling hot-swapping of field devices without halting network operations; this is achieved through shared device names and addresses, ensuring the backup assumes control instantaneously upon failure. For controllers, hot standby configurations pair a primary and backup controller that synchronize application data in real-time, facilitating a seamless switchover in under 10 ms if the primary fails. Profinet defines four scalable system redundancy classes—S1 (single controller with redundant devices), S2 (redundant controllers with non-redundant devices), R1 (redundant controllers and devices), and R2 (redundant controllers, devices, and network)—to match varying availability needs while optimizing resource use.[84][85] Media redundancy addresses physical cabling faults in ring topologies using the Media Redundancy Protocol (MRP), standardized in IEC 62439-2. In an MRP ring, one port per device is blocked to prevent loops, and upon detecting a link failure, the ring manager (typically the controller) opens the blocked port to restore connectivity, achieving reconfiguration in less than 200 ms. This protocol supports up to 50 devices per ring and is widely implemented in Profinet IO devices for cost-effective redundancy in linear or star-ring hybrid setups. For enhanced performance, MRP can integrate with device-level redundancy to maintain I/O communication during media faults.[86][87] Parallel redundancy employs the Parallel Redundancy Protocol (PRP), defined in IEC 62439-3, to provide hitless failover for controller-level operations across independent network paths. PRP duplicates frames from the sender, transmitting them simultaneously over two separate LANs to the receiver, which discards duplicates and selects valid ones, resulting in zero recovery time even during complete path failures. In Profinet, PRP is used for controller redundancy by establishing dual communication channels to IO devices, ensuring continuous cyclic data exchange; it is particularly effective in star or tree topologies where ring-based MRP may not apply. Configurations often combine PRP with system redundancy classes like R1 or R2 for comprehensive fault tolerance.[88][83] Since 2020, Profinet has incorporated Time-Sensitive Networking (TSN) features to advance redundancy, particularly through redundant streams for enhanced reliability in converged networks. Based on IEEE 802.1CB (Frame Replication and Elimination for Reliability), TSN enables multiple redundant data streams over Ethernet paths, where frames are replicated at the source and eliminated at the destination to ensure delivery despite single points of failure, with no perceptible interruption. Integrated into Profinet V2.4, this mechanism supports sub-microsecond jitter and cycle times as low as 31.25 μs, managed via the Network Management Engine in TSN-capable controllers and configured through GSDML files. These advancements extend Profinet's applicability to Industry 4.0 scenarios with mixed traffic, providing robust protection for time-critical streams without dedicated hardware.[42]

Cybersecurity Measures

Profinet employs a defense-in-depth strategy to address cybersecurity threats in industrial environments, incorporating multiple layers of protection to safeguard automation networks against unauthorized access, data manipulation, and denial-of-service attacks. This approach aligns with standards such as IEC 62443 and emphasizes network segmentation, secure communication, and proactive monitoring to mitigate risks inherent to Industrial Internet of Things (IIoT) integrations.[89][90] Access control is implemented through mechanisms like Virtual Local Area Networks (VLANs) for logical network segmentation, which isolates sensitive production cells and restricts lateral movement by potential intruders. Firewalls and managed switches further enforce granular policies, limiting device discovery and configuration to authorized engineering tools. For enhanced authentication, Profinet Security Classes 2 and 3 utilize certificates to verify devices and operators, preventing unauthorized engineering changes during commissioning or maintenance.[89][91][92] Encryption protects data integrity and confidentiality, particularly for acyclic communication such as configuration and diagnostics, using protocols like IPsec for end-to-end secure tunnels or Datagram Transport Layer Security (DTLS) for real-time Ethernet traffic. Cyclic real-time data can optionally employ these in Security Class 3 to counter eavesdropping or tampering in converged IT/OT networks. The PROFIBUS & PROFINET International (PI) Security Guideline provides comprehensive recommendations, including adherence to NAMUR recommendation NE 153 for IT security in automation, which guides secure engineering practices like role-based access and secure boot processes. Additionally, PI's firmware signing service, introduced in 2023, digitally signs General Station Description (GSD) files to ensure their authenticity and prevent injection of malicious configurations during device integration.[89][92][93] Threat mitigation focuses on filtering and detection to address protocol-specific vulnerabilities. Discovery and Configuration Protocol (DCP) filtering, often configured as read-only mode on switches, blocks unauthorized write commands that could alter device names or IP addresses, reducing risks from spoofing attacks. Anomaly detection in real-time (RT) traffic is supported through event logging and intrusion detection systems (IDS), which monitor deviations in cyclic data patterns to identify potential disruptions like man-in-the-middle or replay attacks.[89][90][94] Post-2022 enhancements have strengthened Profinet against evolving IIoT threats, including ransomware, through the PROFINET Specification V2.4 MU6 released in 2025, which mandates Security Classes 2 and 3 with built-in protections like symmetric key updates and secure application relations (AR) startup. These updates include expanded certification testing for robustness against DoS and unauthorized access, alongside PI's establishment of a Cyber Security Incident Response Team (CSIRT) for rapid vulnerability handling. Such measures ensure resilience in hybrid environments, where ransomware could otherwise encrypt control data and halt operations.[92][91][95]

History and Development

Origins and Early Versions

PROFINET originated as an initiative by PROFIBUS & PROFINET International (PI), the user organization for industrial communication standards, to create an Ethernet-based successor to the widely used PROFIBUS fieldbus system. Discussions for this transition began at the PI general meeting in 2000, driven by the need to leverage Ethernet's higher speed and openness for industrial automation while maintaining compatibility with existing PROFIBUS infrastructure.[5] PI, founded in 1989 to promote PROFIBUS, assembled working groups comprising over 500 engineers from leading automation vendors to develop the standard, ensuring it addressed real-time requirements for factory floors.[5] The initial specification, PROFINET Version 1.0, was released in 2003 and incorporated into the International Electrotechnical Commission (IEC) standards under IEC 61158 and IEC 61784, marking its formal standardization as an open Industrial Ethernet protocol. This early version focused on real-time data exchange for device-level communication, enabling seamless integration of sensors, actuators, and controllers in automation systems. Key contributors to PI's consortium included major players such as Siemens, which led much of the technical development; Rockwell Automation; and Schneider Electric, whose involvement helped broaden vendor support and interoperability.[38][96] Early milestones included the definition of PROFINET conformance classes in 2006, which categorized devices into Classes A, B, and C based on real-time performance needs, starting with basic cyclic I/O for Class A to support straightforward factory applications. In 2007, integration of PROFIsafe—the safety communication profile originally developed for PROFIBUS—extended to PROFINET, achieving IEC 61784-3-3 certification and enabling safe operation over Ethernet without additional hardware. Initial adoption centered on discrete manufacturing sectors like automotive assembly and machine building, where PROFINET's real-time capabilities improved cycle times and diagnostics over legacy fieldbuses.[13]

Recent Advances and Future Directions

In 2019, PROFIBUS & PROFINET International (PI) released version 2.4 of the PROFINET specification, introducing native support for Time-Sensitive Networking (TSN) to enhance deterministic communication in converged networks by synchronizing traffic and reducing latency for real-time applications.[97] This update built on prior isochronous real-time (IRT) capabilities from earlier versions, enabling cycle times as low as 31.25 μs in high-performance scenarios.[98] Additionally, PROFINET over Advanced Physical Layer (APL) emerged as a key advancement in 2021, providing a two-wire, intrinsically safe Ethernet solution for process automation environments, allowing seamless extension to hazardous areas without additional infrastructure.[99] Recent integrations have expanded PROFINET's interoperability with higher-level protocols. OPC UA PubSub complements PROFINET by enabling publisher-subscriber messaging for efficient, real-time data exchange in IIoT architectures, facilitating vertical integration while leveraging PROFINET's field-level determinism.[100] For mobile applications, PI members like Siemens introduced PROFINET transmission over private 5G networks in 2022, supporting low-latency communication for automated guided vehicles (AGVs) and mobile robots in dynamic production settings.[101] Looking ahead, PROFINET is evolving toward intelligent, sustainable automation. AI-driven diagnostics, such as Procentec's SNAP platform, analyze network data to detect faults in under two minutes, improving predictive maintenance and uptime.[102] Sustainability efforts center on the PROFIenergy profile, which standardizes power management to reduce consumption by up to 80% during production pauses, aligning with global energy efficiency goals.[103] Market adoption continues strongly, with PI reporting 78.8 million PROFINET nodes installed worldwide by the end of 2024, reflecting a 9.5 million node increase that year.[104]

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