Protocols and Their Application

Here’s a quick overview table for your Question of “Which Industrial Protocols to Use Where” along with a layered integration scheme from ERP ↔ MES ↔ SCADA ↔ PLC.

System Level Protocol Type Examples Purpose
ERP Level (Enterprise) B2MML, REST/JSON, SOAP, APIs SAP, Oracle, Dynamics Integration with external systems, resource management
MES Level (Manufacturing Execution) OPC UA, REST API, ISA-95 Siemens Opcenter, Wonderware MES Management of production processes
SCADA Level OPC UA/DA, MQTT, Modbus TCP, DNP3 WinCC, Ignition, iFIX Monitoring and control of equipment
PLC / Field Devices Level Modbus RTU/TCP, CAN, PROFIBUS, PROFINET, EtherCAT Siemens S7, Beckhoff, Schneider Operation of physical devices and controllers
IoT Integration / Edge MQTT, OPC UA over MQTT/HTTP, WebSockets Edge Devices, Cloud Gateways Transmitting sensor data to cloud/API
Building Automation BACnet, KNX HVAC, lighting, security Integration of building engineering systems

Typical Layered Integration Scheme

 [ ERP Systems ]

         ↑ ↑ ↑

(REST API, B2MML, ISA-95)

[ MES Systems ]

         ↑ ↑ ↑

(OPC UA, MQTT, REST API)

[ SCADA Systems ]

         ↑ ↑ ↑

(OPC UA, Modbus TCP, DNP3)

[ PLC / Controllers ]

         ↑ ↑ ↑

(Modbus RTU, PROFIBUS, PROFINET)

[ Sensors / Machines ]

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