On the evening of October 19th, at a dinner hosted by the Foshan Municipal Government for guests attending the 2nd China (Guangdong) International Internet+ Expo, I had the privilege of meeting the General Manager of Huawei Guangdong Province and learning that Huawei provides industrial communication solutions and will be showcasing its products at this expo.
On October 20th, at Huawei's booth, I consulted with Huawei technical staff, hoping to learn more about:
1. What is the scope of communication equipment Huawei provides for industry: Is it all industrial equipment, or only some industrial equipment?
2. For these devices, what underlying communication protocols does Huawei support?
As I understand it, industrial equipment provides data communication solutions in different tiers based on performance requirements such as data transmission response speed, transmission rate, and security and reliability.
Communication solutions with high requirements for response speed and security and reliability, such as industrial bus or industrial Ethernet connections in traditional automation industries (e.g., communication solutions for automated equipment in oil refineries); and equipment that traditional industries do not have communication but will be connected in the future field of smart manufacturing (e.g., oil extraction and logistics, where wired connections were previously costly but can be networked using wireless technology).
I originally thought Huawei's communication solution was for the latter type of device connectivity. But Huawei technicians said their solution addresses communication for all devices, which raises the question:
1. Wireless communication is not as fast or reliable as Ethernet (Huawei technicians also agree with this view).
2. Ethernet is not suitable for devices with extremely high requirements for response speed and reliability (it's uncertain whether this view is still correct now that technology has advanced to this point, but it certainly was a few years ago. As Ethernet develops to a certain stage, this may become a deficiency). That's why Industrial Ethernet was developed.
3. Then I asked the Huawei technicians which industrial Ethernet protocols Huawei's communications support, and they didn't even know that industrial Ethernet existed. Neither of the two technicians knew about industrial Ethernet.
So I'd like to popularize the concept of Industrial Ethernet!
One net to the end
My understanding of Industrial Ethernet began when I was writing a case study for Siemens. One of the cases involved the Puguang Gas Field's gathering and transportation system, which provided a unified network solution for automation and information technology. This solution utilized a combination of wired and wireless Ethernet, suitable for commercial applications, and Industrial Ethernet suitable for industrial applications, in the Puguang Gas Field's unique geographical environment. This achieved a unified network solution (industrial and commercial systems sharing a single network).
When researching the concept of "One Network to the End," I found that the earliest (in the materials I could find) proposal of the concept was put forward by SixNet in 2010 when it was promoting industrial Ethernet, aiming to achieve seamless integration of automation and information.
Before the advent of Industrial Ethernet, the primary method of communication in automation was through buses. However, buses require cabling, and with the widespread adoption of the internet, Ethernet networks have become increasingly prevalent. Utilizing networks for automated communication is a trend, leading many manufacturers to introduce Industrial Ethernet. Industrial Ethernet enables the integration of automation and information technology, achieving seamless network connectivity.
The difference between Industrial Ethernet and Ethernet
Ethernet is primarily used in commercial environments, while industrial Ethernet is mainly used in automation equipment. Automation equipment demands significantly higher real-time performance, determinism, and reliability than commercial environments. In commercial environments, a one-second delay in information transmission is acceptable, while some industrial equipment requires real-time performance with delays not exceeding tens of milliseconds, leading to different network requirements.
Ethernet communication mechanism
Ethernet refers to a network that conforms to the IEEE 802.3 standard and can transmit data over fiber optic cables and twisted pairs. It uses star and bus topologies and has transmission rates of 10Mb/s, 100Mb/s, 1000Mb/s or higher.
The primary cause of latency in Ethernet is collisions, which stem from its use of CSMA/CD technology. In traditional shared networks, because all stations in an Ethernet network are connected using the same physical medium, signal collisions occur when two devices simultaneously transmit signals. To address this, Ethernet mandates that a station must listen for other stations using the same medium before accessing it. If another station is using the same medium, it must wait, resulting in a collision. To reduce the likelihood of collisions, Ethernet commonly employs algorithms such as 1-Persistent CSMA, Non-Persistent CSMA, and P-Persistent CSMA.
Because Ethernet was designed for office automation, it does not fully meet the requirements of industrial environments and standards, and there are still obvious shortcomings in using traditional Ethernet in the industrial field. However, its cost is lower than that of industrial networks, its technology is more transparent, and in particular, its compliance with the IEEE 802.3 protocol has opened up great convenience for various fieldbus manufacturers.
Ethernet's shortcomings
1. Certainty
Because Ethernet's MAC layer protocol is CSMA/CD, collisions are possible on the network. In an industrial network, a large number of collisions necessitates multiple data retransmissions, significantly increasing the uncertainty of inter-network communication and reducing system control performance.
2. Real-time performance
In industrial control systems, after an event occurs, the system must react within a precisely predictable timeframe. Industrial applications demand extremely high real-time data transmission, with updates completed within tens of milliseconds. While Ethernet's CSMA/CD mechanism allows for retransmission up to 16 times in the event of a collision, this collision resolution mechanism comes at the cost of time.
A device going offline could cause a major equipment or personal safety accident.
3. Reliability
Ethernet was designed for commercial use, but when applied in industrial environments, the harsh operating conditions and severe line-to-line interference inevitably reduce its reliability. Therefore, industrial networks require high reliability, recoverability, and maintainability.
Industrial Ethernet solutions
1. Switching technology
Implement an effective collision domain partitioning mechanism for the shared local area network. Connect the various domains using switches to reduce collisions and data transmission errors. This minimizes collisions and improves system determinism.
2. High-speed Ethernet
The occurrence of collisions is related to network load; the higher the load, the greater the probability of collisions. Increasing Ethernet communication speed can reduce network load.
3. IEEE 1588 time synchronization mechanism
IEEE 1588 defines a Precision Synchronization Protocol (PTP) for precise clock synchronization in measurement and control networks, relating to network communication, local computation, and distribution. This protocol is not exclusive, but it is particularly well-suited for Ethernet-based technologies, achieving microsecond-level accuracy. It uses a time stamping mechanism to synchronize local time. Even when synchronization control signals fluctuate during network communication, its accuracy remains satisfactory. This makes it especially suitable for Ethernet-based systems. By adopting this technology, the Ethernet TCP/IP protocol can operate in high-precision network control systems without major modifications. Its accuracy in area buses far exceeds that of existing systems. Furthermore, using Ethernet TCP/IP-based network technology at all levels of an enterprise offers significant advantages.
A simple system incorporating the IEEE 1588 time synchronization mechanism includes at least one master clock and multiple slave clocks. If multiple potential master clocks exist simultaneously, the active master clock is determined according to an optimized master clock algorithm. All clocks continuously compare their clock attributes with the master clock. If a new clock joins the system or an existing master clock disconnects from the network, the other clocks will re-determine the master clock. If multiple PTP subsystems need to be interconnected, this must be achieved using boundary clocks. One port of a boundary clock is connected to a subsystem as a slave port and provides the clock standard for the entire system. Therefore, the master clock of this subsystem is the original master clock of the entire system. The other ports of the boundary clock act as master ports, through which synchronization information is transmitted to the subsystems. The ports of the boundary clock are ordinary clocks to the subsystem.
The precise network synchronization protocol defined by IEEE 1588 achieves a high degree of synchronization in the network, eliminating the need for dedicated synchronization communication when allocating control tasks. This separates communication timing from application execution timing. Due to its high-precision synchronization, the data transmission time fluctuations inherent in Ethernet technology are reduced to an acceptable level, without affecting control accuracy. A major advantage of IEEE 1588 is its representativeness and openness. Because of its openness, many control system suppliers now use this standard in their products. Furthermore, different equipment manufacturers adhere to the same standard, ensuring good synchronization between their products.
Typical Industrial Ethernet Protocols
Typical industrial Ethernet protocols include four types: HSE, Modbus TCP/IP, ProfINet, and Ethernet/IP.
HSE
The FF Fieldbus Foundation released the Ethernet specification, called HSE (High-Speed Ethernet), in 2000. HSE is a combination of the Ethernet protocol IEEE 802.3 , the TCP/IP protocol suite, and FF11. The FF Fieldbus Foundation explicitly positions HSE as enabling the integration of control networks with the Internet.
Modbus
Modbus TCP/IP
Introduced by Schneider Electric, this protocol embeds Modbus frames into TCP frames in a very simple way, combining Modbus with Ethernet and TCP/IP to create ModbusTCP/IP. This is a connection-oriented approach; each call requires an acknowledgment. This call/acknowledgment mechanism works in conjunction with Modbus's master/slave mechanism, giving switched Ethernet a high degree of determinism. Utilizing the TCP/IP protocol, a web-based interface can be made more user-friendly.
ProflNet
In response to the needs of industrial applications, Siemens of Germany released the protocol in 2001. It combines the original Profibus with Internet technology to form the ProfiNet network solution.
ProfiNet uses standard TCP/IP and Ethernet as the connection medium, and employs standard TCP/IP protocol plus application-layer RPC/DCOM to complete inter-node communication and network addressing. It can simultaneously connect to traditional Profibus systems and new intelligent field devices.
Ethernet
Ethernet/IP
Ethernet/IP is a protocol suite suitable for industrial environments. It is the latest member of the two major industry organizations, ODVA (Open Device Net Vendors Association) and ControlNet International. Like DeviceNet and ControlNet, it is a network based on the CIP (Control and Information Protocol). It is an object-oriented protocol that ensures the efficient transmission of implicit (control) real-time I/O information and explicit information (including information used for configuration, parameter setting, and diagnostics) over the network.
In the future, we will provide industrial backbone network solutions. For high-end instruments in traditional automation equipment, the communication performance requirements can reach the level of industrial Ethernet.
As mentioned in the text, with the improvement of network speed, the difference between Ethernet and Industrial Ethernet may not be significant in the future. However, at least for now, there are still differences. In any case, to realize a backbone network for all devices, the following is required:
1. Supports existing industrial Ethernet protocols;
2. Improve network performance and resolve existing Ethernet issues that have already been addressed by Industrial Ethernet;
3. Is it possible to achieve the performance of wireless networks that reach the level of industrial Ethernet in the future?
I believe that only if the first two conditions are met can an industrial backbone network be accepted by industrial enterprises.
