Monitor and Mend Network Health

Everyone Does Diagnostics
Though network health used to be measured mainly by handheld sniffing devices and IT-based protocols, many control systems and intelligent components have added their own diagnostic capabilities. In fact, many managed Ethernet switches can not only gauge their own status and wellbeing, but they're also able to use Modbus, EtherNet/IP, Profinet and other protocols to report directly to SCADA systems being polled and communicating via a combination of Simple Network Management Protocol (SNMP) and OPC methods.

Likewise, one of the main benefits of today's supervisory NMS is that it provides graphical views and topology maps of software functions and network components in a complete graphical user interface (GUI), which can also be dropped right into users' SCADA displays — making it much more likely that they'll use NMS functions.

The new managed Ethernet switches at the University of Virginia's steam plant also have Modbus registers, which means they can communicate directly with the plant's CitectSCADA system, Garst reports. "Previously, it took a lot of translation for managed Ethernet switches to communicate with a SCADA system, but now users can just poll these registers for the status of the switches, or they can be set to report their own bandwidth, power usage or other parameters, which makes them just like any other devices in the control system," he explains. "This helps control engineers a lot because it puts managed Ethernet switches and other network devices in a language and setting that they can understand and use effectively."

Hirschmann's Cooksley agrees. "This makes our old networking black hole a lot less black. We're even developing a managed switch that can be accessed from a smartphone by using an Apple or Android app, and scanning a QR code on the switch to get its status."

Simplicity, Fieldbuses Help, Too
Logically, just designing and building an industrial network that's less complex can make finding and solving its problems faster and simpler, and one of the classic methods for doing this is reducing wiring and components by using fieldbuses, whether Ethernet-based or not. But even simple networks still need to be checked regularly.

"There are two main things users want to know about their networks," says John Wozniak, automation networking specialist at the CC-Link Partner Assn. (CLPA). "Is a cable disconnected or degraded, and are the data packets running on a network good or bad? Fortunately, when disconnects happen and cycle times and errors increase, they can be easily identified by many tools. Even network architecture design software, such as Mitsubishi's GXWorks and Developer, can show the number of devices on a network, and provide reports from each. In addition, CC-Link IE removes a level of complexity by not using switches, and instead employs CC-Link Network Master to perform device diagnostics and maintain overall network health. However, checking millions of individual data packets requires tools like Wireshark and Frontline, which can help determine what's wrong when packets get lost."

Similarly, Joey Stubbs, PE, North American representative of the EtherCAT Technology Group, adds, "We're talking primarily today about Ethernet-based networks. In particular, EtherCAT has a built-in suite of diagnostics that stands out among industrial Ethernet networks. At any time, EtherCAT users can determine each and every node's operating state, each connection's link status, whether it's accessing its memory correctly, the number of nodes on the network, any CRC errors detected by any nodes and their location, as well as any lost frames in the network. With EtherCAT, the user can capitalize on exact localization of faults and a wider suite of diagnostics features than any other network.

"Also, if the user or machine builder needs more diagnostic capabilities, they can use freely available diagnostic tools, such as Wireshark, which can parse the EtherCAT frames to look at commands and responses from a behavioral perspective in the network. These built-in features make diagnosis of errors or issues with exact localization possible without requiring the integration of separate monitoring systems."

Consulting With Dr. IT
Of course, another crucial element of maintaining industrial network health is working closely with IT professionals, who often have more experience dealing with Ethernet networks and the tools and methods for diagnosing and treating them. Chief among these tools is the free network scanning and data packet evaluation software Wireshark and other similar tools.

Phoenix Contact installs cards for using Wireshark in its components, reports Dan Schaffer, network and security business manager for Phoenix Contact. "We use Wireshark in conjunction with our users to check their bandwidth utilization, and determine if and where they need managed Ethernet switches," he says. "It's also important to check what firmware you're running and check your data stream for errors. Later this year, we're releasing our FL View software that uses SNMP on the back end to do many asset management and network visualization tasks, such as looking for switches and IP addresses and learning what they're connected to."

Similarly, system integrator Automated Control Concepts (ACC) in Neptune, N.J., reports it recently repaired a factory automation system that was experiencing network downtime and some system failures. Some of the original PLCs had been replaced with faster models or added new functions, and the HMI was modified to keep up. However, these modifications weren't coordinated correctly, the control network slowed and often shut down, and staff couldn't find the cause.