Suitable Ethernet Topology for Industrial application


Thread Starter

Moro Mal

We have a Current communication set up in Modbus Plus network. We are now trying to migrate the Network Communication between the Quantum PLCs and Momentum PLCs to Ethernet Communication. I am looking at Ring Manager Redundancy but not too familiar with Ethernet networking. Please can someone out there give me some information on which Ethernet topology is most suitable for Industrial application interms of Redudancy purposes also considering cost of implementing it. Please assist
Your decision on selection a network topology should be based on the importance of the following factors: recovery time in the event of single point of failure (cable break, loss of power to a switch, etc.), available paths for cabling between equipment/devices, and cost of required cabling.

Ethernet is one of the most flexible networking technologies, and it offers many different topologies (see To achieve redundancy, you will need multiple network connections.

In a Bus configuration, it is possible to cascade or "daisy chain" switches together, even with parallel network connections. But in the configuration, any one switch is a potential single point of failure.

Mesh type networks are popular with IT, but they are difficult to implement, because of all the extra connections between switches. See the images on the Wikipedia page above, and you will understand. Additionally, the protocols used (STP, RSTP) by the switches to detect a disconnected link and to re-route traffic are complex and slow relative to manufacturing requirements. In the case of RSTP (Rapid Spanning Tree), this process can take several seconds.

Ring type networks are often a favorite, since wiring between devices/equipment is minimized, cable paths are consistent with preferred cable routing, and recovery time is significantly reduced because the number of potential communications paths are limited.

RSTP can be used for ring networks, however you will generally find vendor specific protocols that achieve orders of magnitude improvements on recovery time. If you have enterprise or control room connectivity requirements and need RSTP, most vendors support using one or more switches which can simultaneously maintain ring and RSTP communications.

Also, remember that Cat5/Cat5e/Cat6 twisted-pair links are limited to a little more than 300 feet. If the distance between connected switches are further than this, you will need to use fiber optic cable and switches capable of accepting fiber connections.