Basic knowledge of industrial Ethernet networking equipment
In today’s control systems and factory automation systems, the application of Ethernet has been almost as popular as PLC. But much of what field engineers know about Ethernet comes from their knowledge of traditional commercial Ethernet. The implementation of many control system engineering is even directly carried out by technicians in the IT department. However, IT engineers’ understanding of Ethernet is often limited to the implementation experience of commercial Ethernet in office automation, which may lead to the simplification and commercialization of the implementation of industrial Ethernet in industrial control systems, and can not really understand the significance of industrial Ethernet in the industrial field, nor can they really use the special functions inherent in industrial Ethernet. Often cause the industrial Ethernet field implementation is not thorough, leaving unstable factors to the entire control system.
So what are the factors to consider when choosing the right industrial Ethernet? In simple terms, from the Ethernet communication protocol, power supply, communication rate, industrial environment certification considerations, installation methods, the impact of the shell on heat dissipation, simple communication functions and communication management functions, electrical or optical port considerations. These are the most basic product selection factors to understand. If there are higher requirements for network management of industrial Ethernet, you need to consider the advanced features of the selected product such as: Signal strength, port Settings, error alarm, serial port use, trunk (TrunkingTM) redundancy, ring network redundancy, quality of service (QoS), virtual local area network (VLAN), Simple Network Management Protocol (SNMP), port mirroring, and other functions that can be provided in industrial Ethernet management switches. Different control systems have different requirements for network management functions, and naturally have different requirements for the use of managed switches. Control engineers should choose the industrial Ethernet product suitable for their system according to the design requirements of their system.
The redundant function of industrial Ethernet comes into being because of the high requirement of industrial control network reliability in industrial environment. From rapid generation tree redundancy (RSTP), ring network redundancy (RapidRingTM) to trunk redundancy (TrunkingTM), each has its own advantages and characteristics, and control engineers can choose according to their own requirements. In order to better help you understand and learn the characteristics of industrial Ethernet redundancy technology, let’s first review the development process of Ethernet devices.
Hub
I believe most people are familiar with hubs. Many people use this simple device to connect various Ethernet-based devices, such as personal computers, programmable controllers, etc. The hub receives a message from one port and broadcasts the message to all other ports. For every message that comes from any port, the hub passes it to the other ports. In terms of messaging, hubs are slow and inefficient, and message conflicts can occur. However, the hub is very simple to use – you can actually plug and play. The hub doesn’t have any flashy features, and there’s no redundancy.
Unmanaged Switch
The development of hubs gave rise to a device called an unmanaged switch. It can realize the routing function of messages from one port to another port, which is more intelligent than the hub. The unmanaged switch automatically detects the network speed of each network device. In addition, it has a feature called the MAC Address Table, which recognizes and remembers devices in the network. In other words, if port 2 receives a message with a specific identifier, then the switch will send all messages with that specific identifier to port 2. This intelligence avoids message conflicts and improves transmission performance, which is a huge improvement over the hub. However, unmanaged switches cannot implement any form of communication detection and redundant configuration functions.
Managed Switch
The next generation of Ethernet connected devices is the managed switch. Compared to hubs and unmanaged switches, managed switches have more and more complex features, and the price is much higher – usually 3 to 4 times that of an unmanaged switch. Managed switches offer more functionality and can usually be fully configured through a network-based interface. It can automatically interact with network devices, and users can manually configure network speed and traffic control for each port. Some older devices may not be able to use automatic interaction, so manual configuration capabilities are essential.
Most managed switches usually also provide some advanced features, such as SNMP(Simple Network Management Protocol) for remote monitoring and configuration, port mapping for diagnostics, VLAN(Virtual local Area Network) for grouping network devices, priority ordering for ensuring priority messages pass through, and so on. With managed switches, redundant networks can be built. Using a ring topology, managed switches can form a ring network. Each managed switch can automatically determine the optimal transmission path and alternate path, and automatically block the alternate path when the preferred path is interrupted.