[Abstract]: This paper introduces the composition of enterprise information systems, introduces Ethernet technology, analyzes in detail the application of Ethernet at the device layer and process control layer, and briefly introduces the key technologies and Ethernet protocols. [Keywords]: Information integration, Industrial Ethernet, Real-time performance, Application layer protocol. With the development of network technology, communication technology, computer technology, and integrated circuit technology, the fundamental way for enterprises to gain competitiveness lies in the coordination and overall optimization of all aspects of their business processes. Only by achieving seamless information flow and sharing across all business processes, and ensuring that the enterprise's application systems closely match its business processes and models, can the enterprise proactively or passively reorganize its business processes and respond agilely to market changes. This places increasingly higher demands on enterprise integration technology. The development of fieldbus technology has greatly changed the structure of enterprise control systems. It features openness, decentralization, digitalization, and interoperability, which is conducive to the integration of enterprise automation systems and information management systems. However, due to technological limitations and market interests, fieldbus suffers from shortcomings such as inconsistent standards, high equipment prices, slow transmission speeds, and high secondary development costs. To improve integration with internal enterprise information networks, Ethernet technology has been considered. Most enterprises have already adopted Ethernet solutions at the information layer. Introducing Ethernet technology at the control and device layers is the best solution for achieving seamless connectivity. Traditional fieldbuses suffer from poor interoperability due to protocol inconsistencies, requiring the installation of conversion gateways, which increases costs and is inconvenient. Industrial Ethernet, with its unified standard, provides convenience for various information exchanges. 1. Composition of an Enterprise Integrated Information System The diagram shows the functional model and hierarchical structure of an enterprise information system. The top layer is the decision-making layer, the bottom layer is the field control layer, and the intermediate layers from bottom to top are the monitoring and optimization layer, scheduling layer, planning layer, management layer, and decision-making layer. Each functional block operates with the support of a computer network and database. The enterprise decision-making system provides decision support for the enterprise's medium- and long-term goals and plans for operations and product strategies based on internal and external information; the management system integrates and manages business information at the factory, workshop, and department levels, and forms logical strategies according to the instructions of the decision-making system; the production planning and scheduling system completes functions such as production plan decomposition, production scheduling, and production statistics, forming detailed production plans, production strategies, and process strategies; the monitoring system realizes functions such as process optimization, advanced control, statistical control, and fault diagnosis; and the field direct control system completes the detection and routine control functions of the production process. 2. Industrial Ethernet Technology Application 2.1 Ethernet Ethernet is the earliest local area network and is currently the most widely used and representative local area network. According to the ISO/OSI 7-layer reference model, the Ethernet standard only defines the physical layer and the data link layer. Industrial Ethernet is developed based on commercial Ethernet protocols and standards, and is a product of the combination of Ethernet technology and industrial needs. Ethernet eliminates related network units in its access network, greatly simplifying the network structure. Due to its simple structure, it is easy to maintain and manage, and the network construction cost is greatly reduced. The Ethernet standard has achieved plug-and-play compatibility, becoming a universally adopted network technology. Ethernet can achieve conversion between different working modes, working speeds, and transmission media through the "auto-negotiation" function supported by software. The network topology can be modified at any time according to user needs, and nodes can be added, moved, and roamed at any time. As a common service interface for users, bandwidth expansion and service upgrades of Ethernet become quite simple. Service providers only need to input the user's upgrade requirements into the relevant service processing system, and adjust the required bandwidth through computer software parameters, making the upgrade cost negligible. After the user's access bandwidth is upgraded, it can be naturally connected to the backbone network, eliminating the so-called bottleneck effect. Ethernet's transmission rate ranges from a minimum of 10 Mbit/s to a maximum of 10 Gbit/s, which can fully meet the needs of MAN and WAN networks. If LAN, WAN, and WAN all adopt Ethernet technology, not only is network upgrade convenient, but the protocol conversion that must be performed between different networks is also avoided, thus simplifying the network. Due to the above advantages, Ethernet is widely used in various fields. 2.2 Ethernet Application Analysis at the Bottom Layer Due to its advantages of unified protocol and high transmission speed, Ethernet has gradually replaced fieldbus or combined with fieldbus to form control systems at the bottom layer to achieve the integration of enterprise information systems. The following is a basic block diagram of Ethernet used at the lower level: Each intelligent device is equipped with an embedded Ethernet interface, connecting directly to the Ethernet network as an Ethernet node. Each device has its own assigned IP address, enabling communication between devices without the assistance of other devices. The device's task is to collect field parameters and monitor the equipment. It connects to the upper level via Ethernet, using TCP/IP as the underlying communication protocol, reflecting data to the upper level in real time, quickly, and accurately. Ultimately, the management level adjusts its decisions based on continuously updated information, improving work efficiency. Ethernet's anti-interference design ensures smooth and real-time communication even in harsh workshop environments and facilitates integration with management. Operator stations, engineer stations, the central control room, and controllers are used to monitor the system, configure the field, and implement complex control algorithms. They also process data collected from the field control level before transmitting it to the upper level. The server primarily processes historical data and shares data with the enterprise's MIS and ERP systems to achieve integrated enterprise management and control. Choosing suitable industrial Ethernet network equipment requires consideration of factors such as Ethernet communication protocols, power supply, communication speed, industrial environment certification, installation methods, heat dissipation, basic communication functions and communication management functions, and whether electrical or optical ports are used. This includes the selection of controllers, repeaters, switches, and converters. The backbone network is based on the Ethernet communication standard protocol, using fiber optic cables or shielded twisted-pair cables, and employing industrial Ethernet switches to achieve ring redundancy. Industrial Ethernet has extended from the information layer down to the control and device layers. It is important to note that because the data types and real-time requirements of the enterprise's three-layer network transmission differ, although the entire network uses industrial Ethernet, routers or bridges are still needed between different layers (as shown in the attached diagram). Routers can block broadcast information on the Ethernet, but if the selected router is too slow, it will create a transmission bottleneck. With an Ethernet architecture, the location of controllers can break through the limitations of traditional network architectures; they can be located in the field or in a central control room. Currently, controllers and even remote I/O support increasingly robust Ethernet functionality. Some controllers and remote I/O modules have integrated web servers, allowing information layer users to directly access the current status values ​​of controllers and remote I/O modules, just like control layer users. Manufacturing enterprises adopting Ethernet architecture and open software systems are also known as "transparent factories." Furthermore, the Internet enables real-time remote monitoring of industrial production processes, combining real-time production data with ERP systems and real-time user demands. This transforms production from order-oriented to opportunity- and market-driven "electronic manufacturing," enabling enterprises to adapt to the demands of economic globalization. 2.3 Key Ethernet Technologies: The key technologies Ethernet addresses are real-time performance, determinism, reliability, and security. To ensure real-time performance and reliability, star topology is used instead of bus topology; network segments are created using bridges or routers; Ethernet switches are employed; full-duplex technology is used; a deterministic scheduling layer is added to the Ethernet MAC layer; and QoS technology is used in industrial Ethernet. Due to the harsh conditions of industrial environments, such as machinery, climate, and dust, industrial networks must possess high reliability, recoverability, and maintainability. For enhanced interference resistance, shielded twisted-pair cables or fiber optic networks can be used. During system design, reliability design can improve the reliability of field devices; a ring-redundant Ethernet structure can enhance system recoverability; and an intelligent device management system can be used for online monitoring, diagnosis, and maintenance management of field devices. Safety measures such as enhanced security, airtightness, and potting are implemented for Ethernet field devices (including Ethernet switches installed in the field) to prevent the leakage of electrical energy generated by faults, ensuring system safety. Industrial Ethernet connects the control and management layers, with upper and lower network segments using the same protocol, ensuring interoperability. A two-tier firewall is used: the first layer prevents unauthorized external access, while the second layer blocks unauthorized access to the internal network. Additionally, filtering and login policies can be adjusted based on log records. 2.4 Industrial Ethernet Protocols: Since large-scale replacement of traditional fieldbuses in networks would significantly increase investment costs and waste existing systems, fieldbuses are often combined with Ethernet. Several solutions exist: 1. Wrapping Method: Typical examples include CIP, HSE, and Modbus-TCP/IP. The integration method involves embedding several unchanged fieldbus messages as "user data" into TCP/UDP data frames and then sending them over Ethernet. This eliminates the need for new specifications, is backward compatible, and allows simultaneous transmission of data frames from different fieldbuses. InterBus uses a reverse wrapping method. It embeds TCP/IP data frames into InterBus messages. Because InterBus messages are short, TCP/IP data frames are split and transmitted. This allows InterBus devices to be used in the field without disruption, greatly improving the efficiency of short message transmission during normal operation. Longer messages that need to be split are mainly used to transmit program and configuration information; this type of transmission occurs less frequently and has lower real-time requirements. 2. Gateway and Proxy Server Method: This is a traditional cross-protocol conversion method, with Profit being a typical example in the fieldbus field. It uses gateways or proxy servers to convert information between Ethernet and the fieldbus. 3. Reconstruction Method: This method involves abandoning the existing fieldbus and building a new real-time communication support layer for Ethernet, thus establishing a completely new fieldbus based on Ethernet. IDA is a typical example. 3. Conclusion With the rapid development of information technology, in order to maintain a leading position in the competition, management needs to have timely access to real-time information from the production equipment layer for decision-making and management. While traditional fieldbuses offer a degree of openness and decentralize functions to the field, allowing intelligent instruments to perform general calculations and control, the lack of a unified protocol among manufacturers for profit necessitates the use of gateways and bridges for protocol conversion. Industrial Ethernet, with its advantages of openness, low cost, and high transmission speed, is gradually replacing or becoming compatible with fieldbuses, achieving seamless integration of information and control networks. With the development of technology, the shortcomings that previously hindered development, such as real-time performance, interoperability, and network security, have been gradually improved, and the widespread application of Ethernet is an inevitable trend. We have reason to believe that in the near future, a unified and interoperable industrial Ethernet will play an increasingly important role in the lower and middle layers of enterprise information integration systems.