A method for process controlling of plants and plant control systems in an OPC UA based Machine-to-Machine (M2M) network is provided. A plant associated with the plant control system a plurality of interlocked elements of one or more operational units of the plant. The operation of an operational unit is controlled by the plant control system using the elements interlocked to the plant control system. The plant control system is accessible by an independent process control system in the Machine-to-Machine (M2M) network via one or more network interfaces, and wherein messages containing signaling data and steering commands are transmitted between the process control system and the plant control system.

Provided is a technology with which it is possible to access a function unit to be accessed without ascertaining an IP address of the function unit. Provided is a unit comprising: a communication unit for relaying a communication between an external device connected to a first network and another unit connected to a second network; a setting unit for acquiring address information of the other unit in the second network from the other unit and generating setting information in which the address information is associated with an identifier which substitutes for the address information; and a link information generation unit for generating, on the basis of the identifier, link information used to access information on the other unit from the external device.

Various embodiments of the teachings herein include a method for deploying a PLC for controlling an IO device utilizing a network proxy. An example includes: intervening in an active connection between a source PLC and the IOD by transparently forwarding messages exchanged; converting the active connection into a passive connection by respectively terminating messages exchanged, assuming control over the IO device from the source PLC, and responding to messages sent from the IOD by the network proxy instead of the source PLC; establishing a second passive connection between a destination PLC and the network proxy for transparently forwarding duplicate messages exchanged between the proxy and the IOD to the destination PLC; and terminating the passive connection between the source PLC and the IOD, converting the second passive connection between the destination PLC and the proxy into an active connection, and assuming control over the IOD with the destination PLC.