The FENA 21 DualPort module supports Three protocols Modbus-TCP, EtherNet/IP, and the PROFInet IO RT network. The Modbus-TCP protocol is simply the Modbus protocol used on top of Ethernet-TCP/IP. Modbus-TCP is an open Industrial Ethernet network which has been specified by the Modbus-IDA User Organization. EtherNet/IP is based on the Common Industrial Protocol (CIP), which is also the framework for both the ControlNet and DeviceNet network protocols. PROFInet IO RT is an open network based on the PI Organization standard.