September 2012
By Bill Lydon, Editor
Is it time for DCS suppliers to use open industrial Ethernet protocol standards for their backbone networks? There are a wide range of open architecture networks, but traditional DCS suppliers have and use their own closed networks. Certainly users have an option when replacing systems to use new hybrid systems that have open architecture industrial Ethernet network protocols but this has tradeoffs.
I have asked major DCS suppliers if they are going to move to open industrial Ethernet protocols. Answers vary from supplier to supplier, but there are a few common issues:
Certainly this is a big issue and if the process network backbone is on a propriety network, it is harder to compromise the controllers. In DCS configurations, workstations and servers have connections through firewalls to enterprise, MES, production and other systems. The critical element is the firewall and if a virus can get through the firewall on this standard Ethernet network, it can get access to the workstations, historians, and other computers in the DCS system. For example, cyber-attacks modeled after Stuxnet are designed to target controllers through the engineering workstations. Researchers say they've never seen anything like it before.
Remember that Stuxnet was brought into the target facility on a USB memory stick. The idea that the propriety network is protected from a cyber-attack may actually create a false sense of security.
The performance argument is that it is not possible to achieve the speed and predictable determinism required when communicating over a standard industrial Ethernet protocol. The DCS systems network backbones were very high speed (i.e. 1 GB) relative to the commercial offerings (when they were introduced), but they are not as fast as Commercial Off The Shelf (COTS) technology available today. Open industrial Ethernet networks today are supporting high speed and deterministic communications and leverage COTS offerings.
Standard fiber optic and switch technology has become commonplace where protection from electrical interference and damage are required.
The argument is that it not possible to achieve the level of redundancy required when communicating over a standard industrial Ethernet protocol. Open industrial Ethernet networks today have multiple options for redundancy and self-healing capabilities.
There is a growing need to communicate information directly between controllers and enterprise systems that is made easy when using standard Ethernet networking. Most industrial Ethernet protocols can coexist with standard TCP/IP network traffic which makes this transparent. Remote maintenance and services are also drivers making it more important to communicate directly with controllers over standard networks. A middle ground may be to have two backbone network connections on controllers, one that is closed architecture for control and one that is open architecture for information.
Today, DCS owners can only directly add controllers to the network from their own controller offerings, which is a limitation. In many DCS configurations users can only interface with other controllers through their DCS vendor’s controller using costly add-ons. Systems with open architecture industrial Ethernet backbones can leverage controllers from other vendors on the same network.
Another trend that is starting to develop is the connection of smart instrumentation from multiple vendors directly to the industrial Ethernet network.
The open architecture trend is established and accelerating but when it comes to critical process control it may take some time to sort out the issues and be able to reliably embrace open network backbones. The good news is users have the option to choose between systems with proprietary backbones or open industrial Ethernet.
