Protocol Stack

General description

A protocol stack is a structured set of communication protocols organized into layers, each with specific functions, to enable effective data exchange between devices in a network. Each layer handles a distinct aspect of the communication process, such as physical data transmission, error detection, routing, and application-level interactions. The stack operates hierarchically, with each layer relying on the services of the one below it while providing services to the one above it. This modular design simplifies development, troubleshooting, and scalability. Common examples include the TCP/IP stack, widely used for internet communications, and the OSI model, which serves as a conceptual framework. 

Structure of protocol stacks

A protocol stack is traditionally organized into layers, each with distinct responsibilities, working together to facilitate seamless communication across a network. The classic structure is often conceptualized using models like the OSI (Open Systems Interconnection) model or the TCP/IP model, which illustrate how data moves between devices. 

1. Physical Layer

This is the lowest layer, responsible for the physical transmission of data over network media, such as cables, radio waves, or fiber optics. It defines hardware standards, voltage levels, and timing. 

2. Data Link Layer

This layer manages data framing, error detection, and correction for reliable transmission between directly connected devices. It includes protocols like Ethernet and Wi-Fi for local area communication. 

3. Network Layer

At this layer, routing and addressing are handled to ensure data packets reach their intended destination across diverse networks. Protocols such as IP (Internet Protocol) operate here, defining logical addresses (IP addresses). 

4. Transport Layer

This layer ensures reliable or efficient data transfer, depending on the application’s needs. Protocols like TCP (Transmission Control Protocol) provide error checking and retransmission, while UDP (User Datagram Protocol) focuses on speed over reliability. 

5. Session Layer (OSI only)

It establishes, maintains, and terminates communication sessions between applications. 

6. Presentation Layer (OSI only)

This layer ensures data is in a readable format for the application, handling encryption, compression, and translation. 

7. Application Layer

The topmost layer where user-facing applications interact with the network. Protocols like HTTP, FTP, and SMTP enable web browsing, file transfers, and email communication. 

Each layer operates independently yet collaboratively, adhering to standardized protocols. This modular design simplifies troubleshooting and enhances compatibility, as changes in one layer do not affect others. In the TCP/IP model, some layers like Session and Presentation are merged into the Application Layer, reflecting a more streamlined, practical approach. 

Important protocols for industrial communication

Industrial communication relies on specific protocols to ensure seamless data exchange and control in automation systems. Protocol stacks for industrial communication must meet stringent requirements to ensure reliable and efficient operation in demanding environments. They must provide real-time capabilities for precise control and synchronization, with low latency and high determinism. Robust error detection and correction mechanisms are essential to maintain data integrity in harsh conditions with electromagnetic interference. The stacks must support scalability to integrate diverse devices and adapt to system expansions. Security features like encryption and authentication are critical to protect against cyber threats. Additionally, compatibility with existing systems and interoperability across different protocols ensure seamless communication within complex industrial automation networks. 

These protocols are categorized into Fieldbus systems, Industrial Ethernet, and IIoT (Industrial Internet of Things) technologies, each suited to different use cases. 

Fieldbus protocols are used for real-time control and communication in industrial devices such as sensors and actuators. They operate on a decentralized network architecture, ideal for environments with strict timing requirements. Key protocols include: 

  • PROFIBUS(Process Field Bus), widely used in factory and process automation for its high reliability and compatibility. 
  • CANopen, derived from the CAN bus, which excels in robust, low-latency communication for motion control and embedded systems. 

  • Modbus (RTU/ASCII), a simple and flexible protocol for serial communication, commonly used in SCADA systems. 

     

Industrial Ethernet or Real-Time Ethernetprotocols combine high-speed communication with determinism, making them ideal for more complex automation systems and real-time data processing. Leading protocols include: 

  • PROFINET, which offers fast, deterministic communication for both factory and process automation, integrating seamlessly with PROFIBUS systems. 
  • EtherNet/IP, which uses CIP (Common Industrial Protocol) for interoperability across devices in automation and process control. 

  • EtherCAT, optimized for high-performance, low-latency control in motion systems and robotics. 

     

The Industrial Internet of Things emphasizes connectivity, analytics, and remote management in smart manufacturing systems. Key IIoT protocols include: 

  • MQTT (Message Queuing Telemetry Transport), designed for lightweight, reliable data exchange, especially in resource-constrained environments. 
  • OPC UA (Open Platform Communications Unified Architecture), a versatile protocol for secure, platform-independent data exchange across industrial devices and enterprise systems. 

Each protocol plays a crucial role in modern industrial systems, with Fieldbus enabling local control, Industrial Ethernet driving high-speed deterministic automation, and IIoT technologies empowering data-driven decision-making and predictive maintenance. Together, they form the backbone of smart manufacturing and Industry 4.0 initiatives. 

Hilscher’s firmware and protocol stacks

Hilscher's netX product family not only stands for pure chip technology, but also for the idea of multi-protocol capability of a single communication solution consisting of hardware and software. 

The protocol firmware for the netX communication controllers is the result of Hilscher's core competence and expertise in communication technology. Over the years, it has steadily evolved into a very broad portfolio of controller and device protocol stacks, including engineering tools for simple and certifiable integration of an automation device into a wide variety of networks. Hilscher benefits from its involvement in numerous technical working groups and committees, which ensures that the netX firmware is always at the cutting edge of technology and is continuously developed further. 

Hilscher provides a full featured set of netX firmware variants for the following industrial communication protocols and standards: CANopen, PROFIBUS, PROFINET, Modbus/TCP, MQTT, OPC UA, EtherCAT, Sercos, VARAN, EtherNet/IP, DeviceNet, CC-Link, CC-Link IE, Ethernet POWERLINK,  

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