Control Engineering and QDS Systems have put up a nice blog tracking the progress on the upgrade of a 10 year old Wastewater SCADA system. This project illustrates the use of the latest technologies and provides a suprisingly high level of detail compared to other writeups I’ve seen on-line:

The SCADA master planned is a three-computer redundant configuration. Computer hardware includes a Dell data center with redundant power supplies, network connections, and mirrored RAID SCSI drives. Two of the servers are responsible for gathering field data from the remote RTUs using Software Toolbox’s Modbus OPC power (TOP) server. Each field RTU is equipped with an Airlink Raven CDMA cell modem. These modems are each assigned a static IP address on the Verizon wireless network. The TOPS server encapsulates Modbus messages within TCP/IP packets and sends them via the Internet to Verizon. The Airlink Modbus capability dis-assembles packets and sends them out the modem serial port to the RTU. The process is reversed to complete the RTU poll. This IP-based design benefits from improved throughput versus traditional sequential polling schemes, allowing up to 16 Modbus RTUs to be polled simultaneously.

Although a “router/firewall/switch” was repeatedly mentioned, the security architecture was not readily apparent. Let’s hope it was left out of the blog but not out of the project design and implementation!