Utilities Distribution

Emulate and study the performance of a radio network for a SCADA system for water distribution in NetSim

The water distribution network has three components

• Remote Terminal Units (RTU): field units that do local process control
• Central Human Machine Interface (HMI): visualization and control of each RTU, and of all RTUs together, from a central location
• An interconnecting network: radios, switches, routers and transport media

Each RTU has a router which acts as a layer-3 device and includes a gateway and a firewall. Each RTU is also a separate IP subnet, so the IP address can encode the location and other information. The HMI is a redundant pair of SCADA nodes. They run as virtual machines on two physical servers at one location, behind a firewall that separates them from the other network components.

Simulation Environment

The team first tested this real-world system in a virtual laboratory. The lab used hardware, software and interconnections as close to the actual system as possible.

The team cloned the HMI VM into the simulation environment. Rockwell Automation's SoftLogix modeled the RTU PLCs, with one VM for each instance of SoftLogix. Each SoftLogix simulated six controllers in a single 17-slot virtual rack. The NetSim emulator connected these two components and emulated the 3rd component, the radio network.

Conclusions

In this virtual lab, the team built many test scenarios and ran them repeatedly, for normal and perturbed operation. The impairment scenarios included:

• escalating latency
• bandwidth constriction at different points
• jitter tolerance
• packet loss and packet reordering
• route loss and fail-overs
• identification of single points of failure

The team then chose the best design from the simulation results.