Part One
Advantages and functions of industrial Ethernet solutions
Currently, manufacturing plants around the world rely on Ethernet solutions to meet the real-time performance and durability requirements of industrial applications. Compared to traditional fieldbuses, Ethernet offers faster speeds, handles large volumes of data better, and ultimately saves money through superior energy efficiency and more efficient equipment. Ethernet can also stand alone as the sole networking technology to connect shop floor automation systems to enterprise IT systems used to control the shop floor—simplifying overall network design while improving performance.
Why does Ethernet play such a significant role in manufacturing, and how does it do so? There are several reasons for the rise of Ethernet, but a few are worth noting:
To avoid collisions, most industrial Ethernet networks currently operate in full-duplex mode. While collisions can occur in half-duplex mode, they are unlikely to pose a problem as long as the ratio of conflicting frames does not exceed a certain threshold. Full-duplex mode completely avoids collisions.
As with other common industrial Ethernet environments (such as wind farms and oil and gas refineries), factory environments and operating conditions are typically very harsh. Operators need to consider vibration, particulate matter, and extreme temperatures, which can be achieved by deploying industrial Ethernet cables and connectors in automation and control systems.
Industrial Ethernet offers a variety of topology and protocol options. Factories can break free from the limitations of the star topology that dominates commercial Ethernet, for example, by adopting a ring topology for redundancy and rapid recovery. Furthermore, protocols such as EtherNet/IP® and EtherCAT® support a wide range of application scenarios and system designs.
Ethernet in the field of automation: past and future
Standardization and performance create differences
Ethernet originated decades ago, and the technology has fostered a strong group of manufacturers and spawned a rapidly evolving product ecosystem. With the improvement of Ethernet performance, the combination of speed and maturity makes Ethernet increasingly likely to replace protocols developed for serial interfaces.
Take, for example, the development of controllers and switches used to support Ethernet-based automation systems. Today's chips can be modified via real-time operating systems to support deterministic processing, and their I/O controllers are specially configured to support any industrial automation protocol, from EtherNet/IP to Modbus/TCP.
These products offer a glimpse into the role of Industrial Ethernet in modern manufacturing plants. They optimize cycle response times while preventing unnecessary outages. As an added advantage, Ethernet vendors and standards bodies provide ongoing support for solving a range of challenges through automation solutions.
Both Ethernet and wireless networks offer bandwidth exceeding that of most dedicated automation networks, and their continued development largely depends on existing standardization organizations and a large network of vendors. Specifically, Ethernet has demonstrated its powerful ability to reliably transmit the right data to the right place at the right time, while manufacturers are widely using wireless instrumentation to address various business challenges, such as improving process performance, reliability, and efficiency, and meeting government directives. — Chantal Polsonetti, Vice President of ARC Advisory Group, in a 2013 article for AutomationWorld.
Ethernet's unique performance characteristics also make it suitable as the foundation for automation systems integrated with the Internet of Things (IoT). The future of IoT largely depends on leveraging real-time data and activity, rather than historical information, to support decision-making. As Polsonetti points out in his article, the shortcomings of the machine-device level can be overcome by improving the system layer.
Part Two
Ethernet/IP in total plant automation
For startups, Ethernet solutions offer significant advantages, including energy efficiency and freedom of choice in equipment. These advantages stem from the flexibility of the underlying technology, decades of development, and the maturity of the supplier base.
In this section, we'll look at EtherNet/IP® and examine how to implement it in plant-wide automation and control systems. This standard, based on Ethernet, is largely compatible with existing infrastructure, making it an excellent choice for improving plant performance and optimizing cost control.
In a highly competitive manufacturing environment, a single system architecture employing open, industry-standard networking technologies is crucial to achieving the necessary flexibility, visibility, and efficiency. —An explanation from a joint publication by Cisco and Rockwell Automation in 2011.
Ethernet/IP is the foundation of automation.
— An application layer protocol that is simultaneously designed for workshop and enterprise networks
In a November 2013 survey on "Mobility, Ethernet, and Wireless Networks," Control Engineering magazine interviewed 200 respondents and found that EtherNet/IP was the most widely used industry protocol, far ahead of other protocols in the field. Over 70% of respondents stated that their facilities used EtherNet/IP.
The popularity of EtherNet/IP varies across industries, such as mining and automotive manufacturing. Specifically, in total plant automation, EtherNet/IP can support the convergence of various applications while ensuring real-time performance. With comprehensive Ethernet deployment throughout the factory, EtherNet/IP can connect industrial and office communications.
EtherNet/IP can be implemented based on Cisco and Rockwell Automation's Converged Plantwide Ethernet (CPwE) architecture, a reference architecture for industrial network design. Its goal is to integrate industrial automation and control system applications with a broader enterprise network through standard device-oriented network services. EtherNet/IP makes this possible.
When implementing EtherNet/IP across the entire plant, a special design is required for the network structure. This design must be based on the functionality of each device and its potential performance and availability requirements, including a Layer 2 and Layer 3 multiplexer hierarchy and a regional segmentation scheme. The lowest layer contains actuators and robots, while applications such as drives and batch control reside at the next higher layer, with the enterprise network at the top.
Delving into the nuances of this EtherNet/IP configuration reveals that VLANs can be used to separate industrial and non-industrial traffic, and firewalls can isolate production and enterprise areas. Furthermore, managed industrial Ethernet switches provide essential network resilience, loop prevention, multicast management, diagnostics, and other services. Gigabit fiber uplinks and redundant paths, along with a logical topology based on the factory's physical layout, strongly support this resilient network.
Advantages of EtherNet/IP-based converged plant-wide Ethernet
Experienced factory operators have ample EtherNet/IP configuration resources. Furthermore, EtherNet/IP uses unmodified standard Ethernet technology, which facilitates this process.
What benefits can the CPwE-based EtherNet/IP implementation guide bring to enterprises?
The fundamental advantages of using Ethernet-based protocols like EtherNet/IP stem from the cost advantages, flexibility, and maturity of Ethernet and IP technologies. Modular standards for distributed automation using existing technologies also offer similar advantages. These advantages help solve problems such as:
System maintenance: Ethernet is a good alternative to traditional automation and control systems because it is easier to integrate with enterprise systems and has lower maintenance costs. Furthermore, talent and expertise in Ethernet and IP technologies are more readily available.
Data Management: Employing Ethernet-based protocols can improve availability, performance, and real-time characteristics. Using a single network can simplify data management across multiple applications and systems.
Integration with business processes: Connecting the shop floor and enterprise systems helps accelerate the decision-making process. Plant-specific design and extensive validation mechanisms ensure reliability and sustainability.
Finally, using Ethernet protocols like EtherNet/IP for plant-wide automation can meet the requirements for deterministic performance while also allowing for the adoption of easy-to-maintain Ethernet and IP standards. Industrial Ethernet combines powerful capabilities with convenience, continuously surpassing traditional fieldbuses, thus becoming a viable option for the automation industry.
Part Three
ModbusTCP and PROFINET
Essentially, CPwE is designed to help manufacturers navigate the complexities of different traditional serial networks and achieve the necessary service integration, ease of maintenance, and high availability, preparing them for application cases such as the Industrial Internet of Things (IIoT). By integrating IT and control engineers with the systems they are responsible for, CPwE can maximize the optimization of industrial operations, significantly improve raw material utilization, and ensure timely delivery of products and services.
EtherNet/IP® has become the primary carrier of CPwE because it bridges the gap between Cisco's Ethernet-to-the-factory framework (including security and networking architecture) and Rockwell Automation's Logix control platform and FactoryTalk platform. Industrial Ethernet switches in CPwE implementations integrate common industrial protocols through native support for EtherNet/IP.
EtherNet/IP achieves this comprehensive end-to-end network integration using unmodified standard Ethernet technology, something custom fieldbuses cannot provide. Cisco and Rockwell have collaborated to enable support for IEEE 802.11 Wi-Fi-based WLANs, optimizing CPwE implementations. These WLANs offer fine-grained quality of service and traffic prioritization features, helping to overcome interference and coverage degradation issues commonly found in industrial wireless networks.
EtherNet/IP, Modbus®TCP, and some forms of PROFINET® are designed with standardization and can interact via CPwE.
This time, we'll turn our attention beyond EtherNet/IP to other industrial Ethernet protocols that provide some support for standard networks. After all, part of CPwE's value proposition is to facilitate interconnection and interoperability between IAC networks that primarily communicate in a Layer 2 LAN model. EtherNet/IP, ModbusTCP, and parts of PROFINET are standardized designs that can achieve this level of interoperability through CPwE. Ethernet, IP, and TCP/UDP can be used at Layers 2, 3, and 4, respectively, for communication between network devices running standard protocols.
ModbusTCP and PROFINET for interoperable interconnected networks
Let's look at two Ethernet-based solutions: ModbusTCP and several versions of PROFINET. These solutions can interact with EtherNet/IP and other protocols such as HTTP, FTP, Telnet, etc., without requiring non-standard network interface cards and/or switching infrastructure. Both standards are very popular; as of January 2015, PROFINET accounted for 8% of all industrial networks, while ModbusTCP held a 3% market share in the same market.
Modbus TCP
ModbusTCP is a widely used, vendor-independent variant of the Modbus protocol, originally proposed by Schneider Electric in 1979. While Modbus uses a serial connection, ModbusTCP uses Ethernet as its physical network and supports data exchange over IP networks in the form of a TCP/IP stack. ModbusTCP was included in the standard in 1999 and can now be integrated into any device that uses a TCP/IP socket.
ModbusTCP employs an open, standardized design, making it an optimal choice for interoperable environments. It can operate on a standard PC Ethernet card and boasts excellent future adaptability thanks to a dedicated Ethernet port 502. Modbus is an open project, originally developed by Schneider Electric and now managed by the Modbus organization (since 2004), with a broad community of vendors working to develop cost-effective solutions.
By using TCP/IP instead of UDP, ModbusTCP enables a large number of concurrent connections and low-maintenance control of data transactions. Thus, unlike its predecessors in the Modbus series which employed stateless transactions, ModbusTCP emulates the simplicity principles of the World Wide Web.
The primary reason for using TCP/IP in ModbusTCP is to achieve continuous control over each 'transaction' by encapsulating transactions within connections that can be identified, monitored, and canceled without requiring any specific actions from client and server applications. This allows the mechanism to tolerate significant variations in network performance and easily adds security features such as firewalls and proxies. —An explanation from a real-time automation guide for ModbusTCP.
PROFINET
We've discussed PROFINET in several other entries, so we won't delve into all its features here. However, it's worth noting that its design—support for standard TCP/IP, and a special stack that can bypass TCP/IP and transmit real-time data via PROFINET I/O and IRT—is particularly well-suited for balancing the convenience of office Ethernet with the needs of industrial networks.
Like Modbus TCP, PROFINET is primarily used for industrial automation process control. It supports optimized cabling (e.g., via Siemens' FastConnect system), achieves deterministic performance over WLAN, and is compatible with star, tree, and ring topologies (outside of linear fieldbus layouts). These features make it a popular choice for simplifying the layout of modern IAC systems and improving their performance. Furthermore, PROFINET can be easily converted from PROFIBUS, the most widely used fieldbus and industrial network protocol, making its integration straightforward for many manufacturers.
PROFINET, ModbusTCP, and EtherNet/IP are excellent examples demonstrating how to build demanding, scalable industrial automation networks based on ubiquitous technologies like Ethernet. In factories, Ethernet's advantages have always been its familiarity and flexibility—it can unify industrial and office networks, surpass fieldbus in critical areas like bandwidth, and directly support TCP/IP. In the future, the continued development of architectures like CPwE and projects such as Time-Sensitive Networking (TSN) will not only expand the application of Ethernet in the automation industry but also further improve factory efficiency.
