MOXA's EDS-508 EtherDevice Redundant Switch offers high-speed self-healing Ethernet technology. For industrial automation applications, redundancy is always an important issue to help increase the reliability of the system. The device comes equipped with a network redundant protocol - 'Turbo Ring' - developed by Moxa, that can help users build up redundant Ethernet networks easily. With its ultra high-speed recovery time, once any segment of a network is disconnected, the automation system will be back to normal in only 300 ms.
For some systems, it may not be convenient to connect all devices in the system to make a BIG redundant ring, since some devices could be located in a remote area. The 'Ring Coupling' function of Turbo Ring can help users separate those distributed devices into different smaller redundant rings, but in such a way that they can still communicate with each other.
IGMP (Internet Group Management Protocol) is important in industrial networking, and may be used with some fieldbus protocols over Ethernet such as Allen-Bradley, EtherNet/IP, Siemens Profibus, and Foundation Fieldbus HSE (High Speed Ethernet). These industrial Ethernet protocols use publisher/subscriber communications models by multicasting packets that could flood a network with heavy traffic. IGMP Snooping provides the ability to prune multicast traffic so that it travels only those end destinations that require that traffic and reduces the amount of traffic on the Ethernet LAN.
VLAN eases network planning
A VLAN is a flexible group of devices that can be located anywhere in a network, but which communicate as if they are on the same physical segment. With VLANs, users can segment the network without being restricted by physical connections - a limitation of traditional network design. Besides, all automation systems incorporate sensitive devices that must be protected from unauthorised access, it is very important to have some type of authentication system set up that only allows authorised users to access the system. If devices belong to different VLANs, they cannot communicate to each other, thus provide extra security and protection from unwanted invasion or traffic. Use the IEEE 802.1Q standard - and GVRP protocol can exchange the same interoperable parameters to keep consistent VLAN setting of the entire network.
Quality of Service (QoS) provides the traffic prioritisation capability to ensure important data to get consistent, predictable delivery. EDS-508 series can inspect both IEEE 802.1p/1Q layer 2 CoS tag, and even layer 3 TOS information to provide the consistent classification of the entire network. With the capability of QoS from EDS-508 series will improve industrial network performance and determinism for mission critical applications.
Every single device should not occupy the bandwidth illimitably, especially if it is malfunctioning. The most well-known problem is the broadcast storm caused by wrong topology or malfunctioned devices. The EDS-508 series not only can prevent the broadcast storm but also can configure the ingress/egress rate of unicast/multicast/broadcast packets, thus helping the administrator to fully control the limited bandwidth and prevent the unpredictable fault in advance.
The EDS-508 series can configure protected static MAC address to specific port. With Port Lock function, these locked ports will not learn any more address but only allow the traffic that comes from the presetting static MAC address, thus helping to block the unwanted invasion or incautious usage.
Sometimes a network is so large that it is difficult to achieve the expected communications behaviour. Industrial communications applications use more of a command-response style than the file-transfer style used in office network environments. This means that when first setting up an industrial Ethernet network, control engineers may need to use a second port to monitor the actual activity between their devices and computer host. This mirroring port function of EDS-508 series helps to ensure that the system behaves as expected.
Since industrial Ethernet devices are often located at the endpoints of a system, such devices cannot always know what is happening elsewhere on the network. This means that industrial Ethernet switch that connects these devices must take responsibility for providing system maintainers with realtime alarm messages. Even when control engineers are out of the control room for an extended period of time, they can still be informed of the status of devices almost instantaneously when exceptions occur.
The traditional way of determining device status is to poll devices periodically, but this is not 'realtime' enough, and is not very efficient. Warning messages must be actively triggered by events. In consideration of these requirements, industrial Ethernet switch must have features such as:
* Through e-mail - The EDS-508 series can send out a warning e-mail when an exception is detected, providing system managers with realtime alarm messages.
* Through relay output - The EDS-508 series provide two relay outputs that can be set up to indicate events with different importance to warn engineers in the field, so they can respond quickly with appropriate emergency maintenance procedures.
DI to integrate other important sensor
With two digital inputs, the EDS-508 series can integrate the sensors into its automatic alarm mechanism, thus turning the warning message onto IP network by e-mail, SNMP trap or OPC.
To reduce the effort required to repeatedly set up IP addresses, the EDS-508 series comes equipped with DHCP/BootP server and RARP protocol to automatically set up IP addresses of Ethernet-enabled devices. Commercial Ethernet switches need 3 to 5 minutes to recover connections when networked devices change their position - this is an unacceptable scenario for industrial applications. The MOXA patented Line-swap fast recovery feature, responds in less than 1 second, keeping communication lines open longer.
The EDS-508 series is easily configured over the network by web browser, Telnet console, or a Moxa provided Windows utility. Moxa's Batch Configurator can also be used to store and copy configuration parameters to multiple EDS-508 units simultaneously.
The SNMP OPC Server software package can convert SNMP into OPC format. The vertical integration of SNMP-management information into existing OPC-based scada-packages gives the customer the ability to build up an Ethernet network management application integrated with existing visualisation and control applications.
For more information contact Robert Wright, RJ Programmable Techniques, 011 781 0777, rob@rjprogtech.co.za, www.rjprogtech.co.za
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