PROFINET technology was developed with key contributions from Siemens and other members of the PROFIBUS user organization PNO. Its compound name stands for “process field network”. PROFINET is the Ethernet-based successor to Profibus DP. The communication system specifies the complete data transfer between I/O controllers, the parameterization, the diagnosis, and the implementation of a network. PROFINET is subdivided into performance classes for a scale of timing requirements: PROFINET RT for no or soft real time and PROFINET IRT for hard real time.