1. Introduction The shift in demand has given rise to Industrial Ethernet. In large-scale control systems, most utilize real-time control networks specifically designed for control systems, known as Fieldbus Systems (FCS). FCS developed in response to the need for intelligent field instruments. Its initial aim was to replace 4-20mA analog transmission technology with digital communication. However, with the development of integrated fieldbus technology and intelligent instrument management (instrument calibration, control configuration, diagnostics, alarms, and recording), FCS has sparked an unprecedented revolution in the control field. Over the past decade, FCS has been the mainstream solution in field-level communication systems for factory automation and process automation. However, with continuous technological advancements, traditional fieldbuses are increasingly demonstrating their inherent limitations. On the one hand, as the intelligence level of field devices continues to increase, control becomes increasingly decentralized. Intelligent devices distributed throughout the factory need to continuously exchange control data, as do those devices and the factory control layer. This has led to a rapid increase in the volume of data exchanged between field devices. On the other hand, with the development of computer technology, enterprises want to integrate underlying production information into a unified plant-wide information management system. Therefore, the enterprise's information management system needs to read field production data and achieve remote service and maintenance through industrial communication networks. Consequently, vertical consistency has become a hot topic. Users want management and field levels to use a unified communication solution compatible with office automation technologies, which can greatly simplify the structure of the factory control system and save on system implementation and maintenance costs. Based on these needs, Ethernet technology has gradually penetrated from the information management layer of factories and enterprises to the lower levels, and Ethernet technology has begun to be applied to control-level communication in factories. Ethernet has advantages such as high transmission speed, low power consumption, ease of installation, and good compatibility. Because it supports almost all popular network interconnection protocols, it is widely used in commercial systems. However, traditional Ethernet is designed for applications with low real-time requirements, such as office automation. It uses a bus topology and Carrier Sense Collision Detection (CSMA/CD) communication. In applications with high real-time requirements, transmission delays occur during the transmission of critical data, a phenomenon known as Ethernet's "uncertainty." Research shows that the transmission delay of commercial Ethernet in industrial applications is between 2 and 30 ms, which is one of the important reasons why Ethernet has long been unable to penetrate the process control field. Therefore, research on Ethernet has practical engineering value, leading to the development of a new type of Ethernet—Industrial Ethernet. 2. Technical Characteristics of Industrial Ethernet Industrial Ethernet generally refers to technology that is compatible with commercial Ethernet (i.e., the IEEE 802.3 standard), but in product design, it meets the needs of industrial sites in terms of material selection, product strength, applicability, real-time performance, interoperability, reliability, anti-interference capabilities, and even intrinsic safety. 2.1 Real-time Performance and Determinism The development of Fast Ethernet and switched Ethernet technologies has brought new opportunities to solve the non-deterministic problem of Ethernet, making this application possible. First, Ethernet communication speeds have increased from 10M and 100M to 1000M and 10G. With the same data throughput, this increased speed means reduced network load and latency, significantly lowering the probability of network collisions. Second, the star network topology divides the network into segments. Ethernet switches, with their data storage and forwarding capabilities, buffer input and output frames between ports, preventing collisions. They also filter data transmitted over the network, ensuring that data transmission between nodes within each segment is confined to that segment, avoiding the backbone and bandwidth usage of other segments, thus reducing the network load on all segments and the backbone. Third, full-duplex communication allows simultaneous reception and transmission of message frames on both twisted-pair cables (or optical fibers) between ports without collisions. Therefore, by using switching hubs and full-duplex communication, collision domains on the network can be eliminated (full-duplex communication), or the probability of collisions can be greatly reduced (half-duplex), thus significantly improving the determinism and real-time performance of Ethernet communication. 2.2 Stability and Reliability Another major problem with Ethernet entering the industrial control field is that its connectors, hubs, switches, and cables are designed for commercial applications and not for harsh industrial environments (such as redundant DC power input, high temperature, low temperature, dust protection, etc.). Therefore, commercial network products cannot be used in harsh industrial environments with high reliability requirements. With the development of network technology, these problems are being rapidly solved. To address the issue of stable network operation under extreme conditions in uninterrupted industrial applications, companies such as Synergetic Microsystems in the United States and Hirschmann and Jetter AG in Germany have specifically developed and manufactured rack-mounted hubs and switches. These are mounted on standard DIN rails, have redundant power supplies, and use robust DB-9 connectors. In June 2002, Moxa Technologies, a Taiwanese company, launched the MOXA EtherDevice Server, an industrial Ethernet product specifically designed to connect industrial devices with Ethernet interfaces (such as PLCs, HMIs, and DCS systems). The recently released IEEE 802.3af standard also defines the bus power supply specifications for Ethernet. Furthermore, in practical applications, the backbone network can use fiber optic transmission, while shielded twisted-pair cables can be used for field device connections. Redundant network technology can also be used for critical network segments to improve network anti-interference capabilities and reliability. 2.3 Industrial Ethernet Protocol Since industrial automation network control systems are not merely communication systems for data transmission, but also automated control systems that utilize the network to perform control functions, they often need to rely on the transmitted data and instructions to execute certain control calculations and operational functions. Multiple network nodes coordinate to complete the automated control tasks. Therefore, it needs to meet the requirements of open systems and interoperability conditions in high-level protocols and specifications such as applications and users. Corresponding to the ISO/OSI seven-layer communication model, the Ethernet technology specification only maps to the physical layer and data link layer. The network layer and transport layer protocols above these are currently dominated by TCP/IP (Transmission Control/Internet Protocol) (which has become the "de facto" standard for the transport and network layers above Ethernet). However, there are no technical specifications for higher layers such as the session layer, presentation layer, and application layer. Currently, commercial computer devices communicate transparently using application layer protocols such as FTP (File Transfer Protocol), Telnet (Remote Login Protocol), SMTP (Simple Mail Transfer Protocol), HTTP (World Wide Web Protocol), and SNMP (Simple Network Management Protocol), which play a crucial role on the Internet. However, the data structures and characteristics defined by these protocols are unsuitable for real-time communication between field devices in industrial process control. To meet the application requirements of industrial field control systems, a complete and effective communication service model must be established on top of the Ethernet+TCP/IP protocol. This requires developing an effective real-time communication service mechanism, coordinating the transmission services of real-time and non-real-time information in industrial field control systems, and forming application layer and user layer protocols acceptable to a wide range of industrial control manufacturers and users, thereby creating an open standard. Therefore, various fieldbus organizations have incorporated Ethernet into the high-speed portion of their fieldbus architectures, utilizing Ethernet and TCP/IP technologies, along with existing low-speed fieldbus application layer protocols, to form the Industrial Ethernet protocol. 3. Applications of TCP/IP-based Ethernet in Industrial Control 3.1 TCP/IP-based Ethernet Ethernet only has physical and data link layer specifications, and it is usually used in conjunction with platform-independent protocols such as TCP/IP. The Ethernet we refer to is actually Ethernet based on the TCP/IP protocol, i.e., Ethernet/IP. Ethernet/IP (Ethernet Industrial Protocol) is an open industrial networking standard introduced by Rockwell Automation. Currently, Rockwell Automation networks generally adopt a three-layer network structure: device layer, control layer, and information layer. In this system, data can flow bidirectionally, layers can exchange data, and for a specific application, one or more layers can be selected, and there may be overlap between layers. The aim is to adopt an open, flat network architecture that meets the needs of high-performance systems and reduces overall system costs (including improving network/device diagnostic capabilities, reducing wiring, installation, and system debugging time, and improving error correction capabilities), as shown in Figure 1. [align=center] Figure 1 Rockwell Automation Network Three-Layer Architecture[/align] 3.2 Application Case The PLC system of Guangzhou Water Supply Company's Xizhou Water Plant uses Rockwell's PLC system. The water intake pumping station of Xizhou Water Plant is located on Liuwuzhou Island in the lower reaches of the Dongjiang River, far from the plant area, more than ten kilometers away from Xizhou Water Plant. For production scheduling needs, the PLC system of Liuwuzhou Water Intake Pumping Station must communicate with the PLC system of Xizhou Water Plant, but there is no communication cable across the river to connect with the outside world. Therefore, Liuwuzhou Water Intake Pumping Station forms a wireless Ethernet network with Xizhou Water Plant through microwave communication. This wireless Ethernet realizes two main functions: first, industrial Ethernet communication between PLC systems, used to transmit real-time production data; and second, production scheduling communication, used to transmit production monitoring images and IP telephone data. At the Xizhou Water Plant, not only can detailed real-time production data from the Liuwuzhou Water Intake Pumping Station be obtained, but real-time images of the Liuwuzhou Water Intake Pumping Station can also be received. Xizhou Water Plant staff can also communicate with staff at the Xintang Water Plant and the Liuwuzhou Water Intake Pumping Station using IP phones to relay production scheduling orders. The network structure of this wireless Ethernet is shown in Figure 2. [align=center] Figure 2 Wireless Ethernet Network Structure Diagram of Xizhou Water Plant[/align] 4 Development Trends and Prospects of Industrial Ethernet Currently, Ethernet has been widely used in the resource management layer and execution manufacturing layer of integrated automation systems in industrial enterprises, and is showing a trend of extending downwards to be directly applied to industrial control sites. In the future, industrial Ethernet will play an increasingly important role in the interconnection and information integration between field devices in integrated automation systems of industrial enterprises. Because industrial Ethernet technology demonstrates a "one-stop" industrial control informatization vision, meaning it can extend all the way to the enterprise's field device control layer, it is widely considered the best solution for future control networks, and industrial Ethernet has become the mainstream cutting-edge technology in fieldbus.