The transfer of data between the two devices is what constitutes a message. The control of the flow of data and how the communication is to be initiated and terminated is defined. That means formal descriptions of digital message formats and rules. This is termed the protocol. A device should indicate the other to start or stop sending data.
Ethernet/IP
This industrial protocol uses the Ethernet structure to connect with various devices like PLCs, robots, sensors, CNC, and other industrial machines. This Ethernet/IP is based on a common industrial protocol. Ethernet/IP used to transfer large amounts of data. The speed ranging from 10 Mbps to 100Mbps at a rate of 1500 bytes per data packet. DeviceNet Vendors Association (ODVA) manages the robust and complex Ethernet/IP.
Modbus TCP/IP
Modbus TCP/IP is a simple Modbus protocol. It runs on Ethernet over a TCP interface. Modbus TCP/IP is an application protocol that assigns the ways of managing and passing data between various layers. When this occurs, the protocol of the next immediate layer has no role. Modbus-TCP is the other name of Modbus TCP/IP. Modbus TCP/IP makes use of Transmission Control Protocol and Internet Protocol for the transmission of messages from Modbus between compatible devices over various systems. Modbus TCP/IP message is actually a Modbus communication data message. It is inside Ethernet TCP/IP cover. TCP/IP is a transport layer protocol. It does not change the way data is stored or interpreted inside the message.
Profinet
PROFINET is an open standard announced by PROFIBUS International. It provides the service definition and protocols for real-time communication based on Ethernet. It is an industrial network standard. Real-time communication protocols are getting more important in networks nowadays. It is using in many real-time and safety-critical application areas. This is because of its characteristic features. Thus it stretches from industrial communication networks to industrial automation level. It facilitates faster, safer, less costly and higher quality manufacturing. It also easily integrates existing systems and equipment while bringing the richness of Ethernet down to the factory floor.
RTE (Real-Time Ethernet) classified into different protocol groups based on the application requirements and real-time capabilities. Considering a group where real-time communication is realized above the MAC layer. And if the achievable cycle time is in the range of 10ms. The typical protocol in this group is PROFINET RT.
Modbus RTU
MODBUS is an application layer messaging protocol. It provides Master/Slave communication between devices that connected together through buses or networks. The client must initiate a MODBUS transaction in order to build the MODBUS application data unit. This function informs the server as to which type of action to perform. The MODBUS application protocol establishes the format of a request initiated by a Master. The function code field is then coded into one byte. It comes within the range of 1 through 255. 128-255 range is reserved for exception responses