The Industrial Ethernet switch is used to connect an Ethernet device. It first receives the data frames sent by a device and then transfers those frames to the appropriate switch ports that are connected to other Ethernet devices. As it passes these frames, it learns and controls the location of the Ethernet device and uses that information to determine which ports to use to transmit frames. This helps to reduce network occupancy.
According to a survey by ARC, the Industrial Ethernet Equipment Market Survey involves a global industrial Ethernet switch that predicts a compound annual growth rate of 49.9% over the next three years. 2004 annual industrial Ethernet equipment for the 840,000 sets (Taiwan), to 2009 will reach 6.7 million sets (Taiwan).
What kind of industrial Ethernet switches are best suited for your plant's current applications? This is really troublesome because of the need to consider a number of factors, such as the work environment, the need for redundancy, network management and non-network management, future maintenance and scalability and so on.
Factors to consider before buying
■ Work environment considerations: including temperature range, EMC electromagnetic compatibility, protection class, installation and power supply. Industrial Ethernet switches are designed for environments that are not suitable for commercial switches, such as environments with extreme temperatures, high vibrations, and strong electromagnetic noise.
■ Select a managed or unmanaged switch: If the network is relatively simple, you can use plug-and-play non-network management switches; if for future maintenance is convenient, you may need to use network management, only the network management switches can be ring topology connection.
■ also need to meet the relevant industry standards: such as marine switches should be consistent with the ship structure standards; if it is dangerous applications, will have to meet the corresponding certification standards; rail transportation and highway and other transportation industries have their own standards.
Network management and non - network management
One of the key questions when choosing an industrial Ethernet switch is to choose a managed switch or an unmanaged switch. While Managed switches are usually more expensive, it provides some extra power. Managed switches contain the characteristics of unmanaged switches.
Managed switches generally support Simple Network Management Protocol (SNMP), and of course, most managed switches do not only have this (SNMP) feature. Basically, Managed switches allow you to control the network, rather than network management switches are usually only allowed to communicate with Ethernet devices.
Managed switches also enable you to monitor the network. Through SNMP, you can view a variety of network status, including the number of bytes received / received, the number of frames received, the number of errors and port status. All of which can be viewed on a port-by-port basis.
Managed switches also have some advanced features that improve your network control capabilities. Such as Quality of Service (QoS), Virtual Local Area Network (VLAN), port mirroring, IGMP Snooping, redundancy and SNMP, are usually only managed by the managed switch. Most of the advanced features of the managed switches are:
■ QoS is the ability of the switch to use high priority for a particular data frame.
■ VLANs allow the switch to logically group the devices and isolate traffic between these device groups even if all devices share a physical switch.
■ Port mirroring Allows one port of the switch to monitor traffic sent or received by one or more ports of the switch. This feature is convenient for real-time monitoring of communication data, is commonly used in Ethernet fault detection method.
■ IGMP Snooping automatically sends multicast frames only to devices that request these frames, which prevents multicast frames from being sent to devices that do not request these frames.
■ SNMP is a simple network management protocol, which allows network management applications in a standard way and switch communication, request status information and configuration configuration. Some vendors also provide network management programs that can convert SNMP data into OPC data used in the system.
■ Ring redundancy is a common feature of managed industrial Ethernet switches. Many industrial switch manufacturers have created their own dedicated ring network redundancy protocol.
In terms of transmission media, most industrial Ethernet communications are carried out via twisted pair, but sometimes fiber cables are required. The cable is required when the signal transmission distance exceeds 100 meters supported by the twisted pair. Multi-mode fiber communication distance of up to 2 km; single-mode fiber communication distance of up to 15 km. Because of its poor communication or magnetic field, cable is also commonly used in high-noise environments.