It is essential to grasp several key protocol concepts.
1. TCP Native (RFC 793)
- Definition: The standard Transmission Control Protocol, defined in RFC 793, providing a connection-oriented, reliable, byte-stream-based transport layer.
2. ISO on TCP (RFC 1006)
- Definition: ISO transport protocol layered over TCP, detailed in RFC 1006, aligning with the ISO-OSI model’s transport layer (Layer 4).
3. UDP (RFC 768)
- Definition: User Datagram Protocol, connectionless and unreliable. Sends datagrams without guaranteed delivery or ordering
RFC 793 vs. RFC 1006 vs. RFC 768
| Protocol | Defined By the specification document | Connection Type | Key Characteristics |
|---|---|---|---|
| TCP (Native) | RFC (Request for Comments) 793 | Connection-oriented | Reliable, stream-based; no frame markers—requires careful LEN use in TRCV |
| ISO on TCP | RFC 1006 | Connection-oriented | Adds frame boundaries and acknowledgments—better for structured comms |
| UDP | RFC 768 | Connectionless | Fast and stateless, no acknowledgments—used for simple or broadcast messaging |
Top 9 Industrial Communication Protocols
our Principal and Senior Control System Engineers routinely see even on a single plant floor:
- PROFINET IRT closing servo loops inside a packaging cell and coordinating multiple drives.
- EtherNet/IP orchestrating a vision inspection system alongside other drives.
- EGD shuffling critical interlock data between GE RX3i turbine and compressor controllers — no polled connections required.
- MODBUS TCP pulling flow totals from an old fiscal meter.
- DNP3 (Distributed Network Protocol) connecting a solar farm inverter to a utility SCADA master over a 900 MHz radio link — time-stamped events, unsolicited reporting, and robust integrity polling over serial or TCP.
- CAN bus in geneset power management: Industrial controllers (like DEIF) designate PM Primary/Secondary units over CAN. Primary and secondary genesets continuously communicate load sharing. CAN handles real-time synchronization of voltage, frequency, and phase angle before grid connection. If the primary fails, the secondary detects lost CAN heartbeat and takes over automatically.
- REST APIs exposing machine status and production counts to a custom dashboard via HTTP/JSON — simple, stateless, and web-native.
- OPC UA unifying all this data into a single, semantically rich namespace for the MES.
- MQTT feeding a cloud historian over a cellular link.
Not chaos — a deliberate, layered architecture designed for purpose.
Here’s a quick guide to nine protocol archetypes in industrial automation:
1️⃣ MODBUS TCP – The Flat Memory Map
Client-server polling of 16-bit registers. Cheap, reliable, and raw — but opaque. Legacy-friendly.
2️⃣ DNP3 – The SCADA Event Logger
Master-outstation with time-stamped analog and binary events, unsolicited reporting, and class-based polling. Designed for electric/water utilities, noisy serial links, and high latency. Far more robust than MODBUS for critical infrastructure.
3️⃣ MQTT – The Topic Tree
Pub/Sub over lightweight topics. Ideal for WAN/cloud telemetry. Payload agnostic, but needs Sparkplug B or similar for industrial context.
4️⃣ OPC UA – The Semantic Graph
Service-oriented, context-rich. Discoverable machines, standardized nodes, companion specs (UMATI, PackML, Robotics). Perfect supervisory/MES backbone.
5️⃣ PROFINET – The Scheduled Real-Time Bus
Provider-consumer with RT/IRT channels. Microsecond-accurate cyclic I/O, module/submodule info model, vendor-agnostic drive control.
6️⃣ EtherNet/IP – The Object-Oriented Controller Bus
CIP implicit/explicit messaging. Deterministic I/O, structured object model. Great for control networks — bridge to OPC UA for semantic richness.
7️⃣ EGD (Ethernet Global Data) – Connectionless Producer-Consumer
Cyclic UDP pushes. Ultra-lightweight peer-to-peer controller data highway. No connections, no polling, no acknowledgements. GE control islands love it.
8️⃣ CAN bus – The Redundant Power Management Bus
Multi-master, message-priority arbitration. In geneset networks, it enables primary/secondary designation, continuous load sharing calculation, real-time synchronization (voltage, frequency, phase angle), and heartbeat-based failover. Fault-tolerant, deterministic, and no IP stack required.
9️⃣ REST APIs – The Web-Native Request-Response
HTTP/JSON, stateless, resource-oriented. Ideal for dashboards, mobile apps, and IT/OT integration — but requires careful rate limiting and security hardening for industrial use.
💡 Key takeaway: Each protocol has a role. Together, they create a cohesive, layered, industrial ecosystem, balancing speed, determinism, legacy support, semantic richness, and cloud integration.
🔧 Need help with these protocols? We offer consultancy and integration services for these protocols, industrial gateways, edge gateways, and protocol conversion. Feel free to DM us.
