MQTT

MQTT is a lightweight messaging protocol designed for efficient communication between devices. It was created to address the challenges of transmitting data reliably over low-bandwidth, high-latency, or unstable networks — conditions commonly found in industrial settings, remote monitoring systems, and embedded devices.

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These characteristics have made MQTT a popular choice in IoT ecosystems, enabling everything from smart home automation to large-scale industrial control systems.

MQTT in Industrial IoT (IIoT) systems

MQTT has become a key messaging protocol for Industrial IoT (IIoT) thanks to its lightweight design and efficient data delivery. Yet despite its strengths, MQTT lacks a standardized way to define and structure data, often leaving developers to build custom logic for every device type. This approach works — but it doesn’t scale easily.

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This is where MQTT Sparkplug comes in. Sparkplug builds on MQTT’s foundation, adding data standardization, state awareness, and improved scalability — all essential for complex IIoT environments.

MQTT Sparkplug

MQTT Sparkplug is an open-source specification designed to bring structure and standardization to MQTT data in industrial environments. Built on top of MQTT, Sparkplug introduces a standardized payload format, a defined topic structure, and a set of state management rules. This ensures that devices, sensors, and software systems all speak the same language to seamlessly integrate data and improve scalability.

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By combining these features, Sparkplug transforms MQTT from a flexible data transport protocol into a robust, self-describing communication standard for IIoT. It eliminates the need for custom parsing logic, reduces integration headaches, and enables true plug-and-play scalability across industrial networks.

Key Differences

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The design of Sparkplug revolves around three key system components: the Edge Node, the Host Application, and the MQTT Broker. Each plays a distinct role in managing data flow and maintaining system state.

Edge Node

An Edge Node is any device or system that collects data from sensors, machines, or other field devices. It acts as the primary data source in a Sparkplug environment.

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This is the MQTT Transmission module

Host Application

The Host Application is the system that consumes data from Edge Nodes. Typically, this is an industrial control system, IoT platform, or data analytics tool.

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This is the MQTT Engine module

MQTT Broker

The MQTT Broker serves as the central hub for all data exchanges. Acting as a message router, it handles incoming data from Edge Nodes and distributes it to Host Applications based on Sparkplug’s standardized topic structure.

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This is the MQTT Distributor module or Chariot® MQTT Server

How MQTT Sparkplug Works

By introducing standardized messaging rules, Sparkplug ensures that data is not only delivered efficiently but also consistently understood across devices and applications. At the core of this system are Sparkplug’s defined message types, topic structure, and state management mechanisms.

MQTT Topic Namespace and Hierarchy

Sparkplug enforces a strict topic structure that organizes data consistently across devices and systems. Each topic follows a predefined format:

Sparkplug's topic format: spBv1.0/<Group ID>/<Message Type>/<Edge Node ID>
spBv1.0 – Identifies the Sparkplug protocol version.
Group ID – Represents a logical grouping of devices (e.g., production line, factory floor).
Message Type – Defines the message purpose (e.g., NBIRTH, NDATA, NDEATH).
Edge Node ID – Identifies the originating device.
This structure simplifies data organization, ensuring that all systems can identify device sources and message types without custom logic.

Payload Format

Sparkplug uses Google’s Protocol Buffers (Protobuf) to encode data efficiently. Protobuf structures data in a compact binary format that reduces bandwidth usage while maintaining flexibility for complex data models.

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Metrics – The actual data points being transmitted.
Timestamps – For precise data tracking.
Metadata – Additional details about the device or data source.
This structured payload eliminates the ambiguity seen in traditional MQTT deployments, where payloads can vary significantly between devices.

Birth and Death Certificates

To maintain system awareness, Sparkplug introduces birth and death certificates.

Birth Certificate (NBIRTH): Sent by an Edge Node when it comes online. This message announces the node’s presence, publishes its available metrics, and signals to the system that the device is active.
Death Certificate (NDEATH): Sent by the MQTT Broker if an Edge Node unexpectedly disconnects. This ensures the system is immediately aware when a device goes offline.

Real-Time State Awareness

Sparkplug’s state management goes beyond simple message delivery. By requiring devices to maintain active connections with the broker, Sparkplug ensures that system state is always known. When devices disconnect, the broker automatically alerts Host Applications by publishing a death certificate — preventing stale or inaccurate data from being mistaken as live.

Unified Namespace for Simplified Data Management

Sparkplug’s structured topics and payloads enable a unified namespace, where all devices adhere to the same data model. This simplifies the integration of new devices, reduces configuration overhead, and ensures data is always delivered in a predictable format — critical for scaling IIoT ecosystems.

Which One to Use?

Plain MQTT is ideal for lightweight IoT deployments where flexibility is key, and devices produce minimal data points.

MQTT Sparkplug is better suited for complex IIoT environments where data consistency, system state awareness, and scalability are critical.

Transmitters

A Transmitter is an agent that monitor tags, converts them to Sparkplug Messages, and publishes to an MQTT Server. 

• Messages can be consumed by any Sparkplug Host Application such as MQTT Engine.
• Any MQTT client created by the agent will publish and subscribe to data using the Sparkplug B protocol.
  • Uses the namespace spBv1.0
  • Using the Sparkplug B protocol provides the benefits of session management including Primary Host ID
  • Understands Ignition UDTs and can be configured to publish UDT definitions in BIRTH messages
  • Is capable of publishing 10s of thousands data messages contain multiple tag change events

UNS Transmitters

A UNS Transmitter is an agent that monitors tags and publishes them as MQTT Messages with a JSON payload to an MQTT Server. 

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