Multiple connections to a single device

Multilink Dual Homing

The need

When one network device, for instance an I/O block or industrial controller, is seen to be critical to a system it makes sense to consider providing dual connections to separate parts of a network. Some industrial equipment has two network interface cards, but in many cases this option is not available. Also with this solution the device has to support a protocol that decides on which network connection to use which can add complexity to the i/o function.

Networking consideration

In any Ethernet network it is important not to accidently create rings. If this happens then network broadcast packets can end up circulating the network endlessly resulting in the ‘broadcast storm’ phenomenon. To provide the most reliable solution it is important that the primary and secondary links connect to separate parts of the backbone network. This kind of connection is defined as dual homing.

The solution

WeOS offers a feature called Multilink Dual Homing that allows more than just a dual connection to the network. It is actually possible to configure as many as eight of these links back to the main network. With this function network solutions can be created offering multiple levels of resilience.
Obviously the switch that connects to the equipment can be seen as a single point of failure, much like the i/o device. It is therefore critical that this switch is designed with the highest level of reliability to ensure maximum levels of network resilience. The best measure of reliability is the MTBF of the product. The Westermo Lynx and Redfox range of products offer industry leading figures exceeding 500,000 hours.