In MQTT 3.1.1, the question “how many QoS 1 messages can I have in flight at once?” had no clear answer. The spec didn’t say. Implementations varied — some Servers accepted thousands of pipelined PUBLISH packets; others would only process one in-flight message per client. Clients that wanted predictable behavior had to assume the worst (one in-flight message… Read More: MQTT 5 Flow Control Explained: Receive Maximum »
For two decades MQTT 3.1.1 gave you one of two answers to every operation: it worked, or it didn’t. When a PUBLISH failed, you got nothing actionable back — just silence or a disconnect. When a SUBSCRIBE half-failed (one topic accepted, one rejected), you couldn’t tell which was which. When the Server kicked you off the network, you… Read More: MQTT 5 Negative Acknowledgements: Reason Codes Explained »
For two decades, MQTT clients authenticated to the Server the same way: send a username, send a password, hope the Server accepts. That worked for the IoT prototypes of the 2000s. It does not work for modern industrial systems where credentials rotate, identities federate, and a plain-text password traveling over the wire is a security incident waiting to… Read More: Enhanced Authentication in MQTT 5 Explained »
If you have used MQTT 3.1.1 for a few years and are wondering what MQTT 5 actually changes, or if you are starting a new deployment and need to decide between the two, this is the article that gets you there directly. The two versions share the same core protocol — publish/subscribe over TCP, three QoS levels, retained… Read More: MQTT 5 vs MQTT 3.1.1: Differences, Features & Migration »
Two protocols dominate industrial Ethernet networks worldwide. Modbus TCP is the most-deployed industrial Ethernet protocol globally — running on millions of devices, embraced for its simplicity and openness. EtherNet/IP dominates the North American market and is everywhere Rockwell Automation has presence — running on the same ControlLogix PLCs that drive most US manufacturing. They both run over standard… Read More: EtherNet/IP vs Modbus TCP: Complete Comparison Guide »
Ten years ago, OT cybersecurity meant “air gap the control network.” That model failed. Modern industrial systems need controllers talking to MES systems, drives reporting to cloud analytics, engineering tools accessing devices remotely. The air gap is gone — and with it, the security model that depended on physical isolation. CIP Security is the ODVA-defined answer for CIP… Read More: CIP Security Explained: TLS, X.509, and OT Cybersecurity »
You buy an EtherNet/IP AC drive from Rockwell Automation. It works with your ControlLogix PLC. You later buy a different AC drive from a different manufacturer — say, Yaskawa or ABB — and it works with the same PLC too. Why? Because both drives implement the CIP AC Drive Device Profile (Device Type 0x02). They expose the same… Read More: CIP Device Profiles Guide: Interoperability Framework »
Twenty years ago, synchronized motion across multiple servo drives required a dedicated motion bus — SERCOS, MACRO, FireWire, or a proprietary fieldbus. The motion network ran separately from the control network because standard Ethernet couldn’t deliver the deterministic microsecond timing motion needs. Today, with CIP Motion running over standard EtherNet/IP, the motion bus and the control network are… Read More: CIP Motion Explained (Class 0x42 Motion Axis Object) »
When a six-axis servo system has to coordinate moves across drives that may be sitting in different cabinets, on different switches, in different rooms — sub-microsecond timing matters. When a sequence-of-events recorder needs to log which fault tripped first across a network of distributed I/O — microsecond timing matters. When a process control application needs to correlate data… Read More: CIP Sync Explained: IEEE 1588 PTP for Industrial Networks »
Open any CIP packet in Wireshark and you’ll see paths encoded as hex bytes — 20 04 24 66 2C 67 2C 68, 20 06 24 01, 34 04 01 00 0C 00 B8 00 04 01. These are CIP path segments — the universal addressing format that tells every CIP service where to go. Class IDs, Instance… Read More: CIP Path Segments Explained: EPATH Encoding for Engineers »