Which Modbus variant is today the most widely used for new installations in a modern IT/OT environment?
C — Modbus TCP (over Ethernet)
Modbus TCP (port 502 over Ethernet) is the modern backbone standard: easy IT integration, ideal across buildings and well supported by current devices. ASCII is wrong because the text encoding doubles bandwidth use for the same payload as RTU and is almost extinct today. RTU is wrong as the single best answer because, although it remains heavily deployed at field level (drives, instrumentation on RS-485 multi-drop), it is no longer the first choice for new IT/OT installations. Modbus Plus is wrong because it is an obsolete proprietary Modicon token ring, not used in new projects. The 2026 trend is a Modbus TCP backbone with Modbus RTU sub-networks where serial field devices already exist.
When designing a new installation, default to Modbus TCP for the supervisor link and only drop to RTU for the last hop to serial-only field devices through a gateway.
- A.Modbus ASCII (text frames over RS-485)
- B.Modbus RTU (binary frames over RS-485)
- C.Modbus TCP (over Ethernet)✓
- D.Modbus Plus (proprietary token ring)
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