Due to the ultra-high requirements of the industrial environment for the reliability of industrial control networks, the redundancy function of industrial Ethernet has emerged. From Rapid Spanning Tree Redundancy (RSTP), Ring Redundancy (RapidRing) to Trunk Redundancy (Trunking), each has its own different advantages and characteristics, and control engineers can choose according to their own requirements. Today, the editor of Feichang Technology takes everyone to understand and learn the features of industrial Ethernet redundancy technology in detail. If you are interested, let's take a look!
Hubs 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, and so on. The hub receives a message from a certain port, and then broadcasts the message to all other ports.
For every message from any port, the hub will pass it to every other port. In terms of message delivery, hubs are slow and inefficient, and message conflicts may occur. However, the use of the hub is very simple-it can actually be plug and play. The hub does not have any flashy functions, nor does it have redundant functions.
Unmanaged switches
The development of hubs has produced a device called unmanaged switches. It can realize the routing function of messages from one port to another, which is more intelligent than the hub. Unmanaged switches can automatically detect the network speed of each network device. In addition, it has a function called "MAC address table", which can identify and remember devices in the network.
In other words, if port 2 receives a message with a specific identification code, the switch will then send all messages with that specific identification code to port 2. This kind of intelligence avoids message conflicts and improves transmission performance, which is a huge improvement over hubs. However, unmanaged switches cannot implement any form of communication detection and redundant configuration functions.
Managed switch
The next generation of Ethernet connection equipment development is the managed switch. Compared with hubs and unmanaged switches, managed switches have more and more complex functions, and the price is much higher-usually 3 to 4 times that of an unmanaged switch. Managed switches provide more functions and can usually be fully configured through network-based interfaces. It can automatically interact with network devices, and users can also manually configure the network speed and flow control of each port. Some old devices may not be able to use the automatic interaction function, so manual configuration function is indispensable.
Most managed switches usually also provide some advanced functions, such as SNMP (Simple Network Management Protocol) for remote monitoring and configuration, port mapping for diagnosis, VLAN (virtual local area network) for grouping network devices, and Prioritization function to ensure the passage of priority messages, etc. Using 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 the backup path, and automatically block the backup path when the priority path is interrupted.
Managed redundant switch The
advanced managed redundant switch provides some special functions, especially optimized for the design of redundant systems with strict requirements on stability and safety. The main ways to construct a redundant network are as follows: STP, RSTP; Ring network redundancy RapidRing
1.
STP and RSTP STP (Spanning Tree Protocol, Spanning Tree Algorithm, IEEE 802.1D) is a link layer protocol that provides path redundancy and prevents network cycles from occurring. It forces the alternate data path to be blocked. If a path fails, the topology can be reconfigured with the help of active backup path and link reconstruction. The recovery time from network interruption is between 30 and 60 seconds. RSTP (Rapid Spanning Tree Algorithm, IEEE 802.1w) is an upgrade of STP, shortening the recovery time from network interruption to 1~2s. The spanning tree algorithm has a flexible network structure, but it also has the disadvantage of slow recovery speed.
2. Ring network redundancy RapidRing was born in
order to meet the strong real-time characteristics of industrial control networks. This is a technology that uses a ring network to provide high-speed redundancy in an Ethernet network. This technology can make the network self-recovery within 300ms after the interruption. It can also remind users of the disconnection phenomenon through the switch's error relay connection, status display light and SNMP settings. These can help diagnose where the ring network is disconnected.
RapidRing also supports two ring networks connected together, making the network topology more flexible and diverse. The two rings are connected by dual channels. These connections can be redundant to avoid problems caused by a single cable error.
3. Trunk redundancy trunking
sets multiple ports of different switches as trunking trunk ports and establishes a connection, then a high-speed backbone link can be formed between these switches. It not only doubled the network bandwidth of the backbone link and enhanced the network throughput, but also provided another function, namely the redundancy function.
If the backbone link in the network has problems such as disconnection, the data in the network will be transmitted through the remaining links to ensure the normal communication of the network. Trunking backbone network adopts bus-type and star-type network structure, and the theoretical communication distance can be extended indefinitely. This technology uses hardware detection and data balancing methods, so the network interruption recovery time has reached a new height, and the recovery time is generally less than 10ms.
Well, the above content is the detailed introduction of Feichang Technology on the industrial Ethernet redundancy function, I hope it can be helpful to everyone! Feichang Technology , a professional manufacturer of optical transceivers, optical fiber transceivers, industrial switches, and protocol converters, independently researches and develops brands, welcome to come to understand and communicate.