It is the author’s opinion that automation of the controls networking and the IT network is inevitable. It became inevitable the moment the controls industry chose to use Ethernet as the medium with which to communicate data. The controls industry may choose to be dragged kicking and screaming into the modern communications era, or it can gracefully embrace the change. Embracing means the controls industry would be able to leverage the myriad rich, existing technologies that have been proven foolproof in the IT world. To be dragged kicking and screaming into the modern automation era would do a terrible injustice to those who have worked diligently to bring it about. This could quite possibly add an entirely new facet to the fieldbus wars, which I hope have not been forgotten.
refer to: http://www.automation.com/leveraging-it-technology-for-industrial-controls-applications