Emerson’s Craig McDaniel provided an overview on the Ovation control system network architecture at the 2017 Ovation Users Group conference. He provided a basic overview of Ovation’s network architecture showing standard configurations, connectivity, redundancy, IP addressing schemes, port assignments, network hardware, and connections to third party equipment will be provided in this session. He also discussed the traffic flow through Ovation and provided a review of some common issues encountered on Ovation networks and how to avoid them.
Network components in an Ovation system include switches, layer 3 switches and routers. Non-Ovation components include printers, time servers and separated from Ovation network are components such as PLCs and human machine interfaces (HMIs).
In a network design, you need to consider the Ovation networks, field PLC networks, plant local area networks, etc. IP addresses must be suitable for the network they are on or clearly defined static route or default gateway paths to other networks. IP addresses cannot overlap between different networks.
Craig discussed network distance limitations. A copper cable end to end is 100-meter length before a switch is required to extend. Multimode fiber can reach up to 2km at 100Mbits/sec or 220-550m at 1Gbits/sec. For single mode fiber, it is 10km at 100mbit/sec and also 10km at 1 Gbits/sec or even 70km at 1Gbits/sec with long haul single mode fiber.
There are 3 different types of Ovation networks—2nd generation, 3rd generation (Fast Ethernet) and 3rd generation (Gigabit). With 3rd generation networks, no fiber media converters on the switch side are required.
3rd generation common architecture support redundancy through separate uplink ports which opens more fan-out ports for network connections. In a virtual environment, both 2nd and 3rd generation networks are supported. A key point is that you cannot mix generations in a network. Ensure the layout drawing match the switch configuration files with device placement and type, root-fanout connections and cross connections. Confirm all drawings and configurations are at the correct revision level and review the switches/routers wiring and that it appears as per the drawing/configuration.
To get communications outside the Ovation local network, there must be a static route or default gateway and a device cannot have two default gateways. A static route is how to get around this need.
Craig transitioned from network design to network troubleshooting. There is an Ovation tool called GatherUI available to Ovation User Group members. It goes and collects information from across the network to aid in the troubleshooting process. From the Ovation operator interface, System Status pages can be created to show the network elements with status highlighting active, standby and offline communications status. This includes nodes on the Ovation networks as well as switches and routers.
The network switch LEDs can also provide information on if a link is communicating or not. Green blinking is working state. Green/amber indicates errors are occurring and it needs to be investigated. No LED lit (black) means no communications are happening. Amber means the link is not forwarding. The log files created by the switch can also provide information that can be useful for troubleshooting and cybersecurity efforts—such as excessive login failures.
Craig noted that troubleshooting involves the network connection itself and the security settings. Security settings can be temporarily lowered to see if communications occur or not. This isolates the problem to either the security settings or something in the network configuration or hardware.