Intro
In this article, we examine the differences between 3 IoT protocols: Lucid, Sparkplug and OPC-UA and ask: “why would you select one instead of another”? Might one of these protocols be enough to do everything and, like Tolkien’s ring “rule them all”?
To support the comparison, we have measured each protocol against a single set of functions. This set of functions are the user requirements put together by UK Water Companies in the early days of producing WITS-DNP3, a common protocol to support their OT objectives. There are 97 separate requirements, which, although sourced from the Water Industry, are general enough to cover many OT and IoT requirements. The aim of the article is to give a broad view of how the three selected protocols implement those requirements.
Intro to the data
The data used to generate the statistics in this article was created by a subcommittee of the WITS Protocol Standards Association. In 2021, whilst involved in the development of Lucid, they performed a line-by-line analysis of the functional features of all 3 of these IoT protocols against the functional requirements discussed above. They noted a simple “yes” or “no” score against each feature indicating whether each protocol supported that feature. A simplified version of that data can be seen here.
Neil Tubman of Terzo Digital took this scoring and, without re-assessing those scores, performed some basic statistical analysis on the data to provide some of the charts and conclusions in this article.
Intro to the protocols
A brief comparison of the three IoT protocols is provided below:
| Protocol | Description | History / adoption |
| Lucid | An Industrial IoT protocol based on MQTT and JSON technologies. Implements most of the features of the WITS-DNP3 protocol. | Formally released in 2023, although draft versions were available beforehand. Still in the early phases of adoption |
| Sparkplug | An efficient and lightweight messaging specification designed for industrial IoT applications. It offers simplicity and scalability, making it well-suited for resource-constrained environments in the industrial automation industry. | Spec released in 2016. Some level of adoption in products but not as widely adopted as OPC-UA. |
| OPC-UA (Unified Architecture) | OPC-UA is an open and platform-independent standard for secure and reliable data exchange in industrial automation systems. It provides a robust and interoperable solution, facilitating communication between devices, sensors, and software applications, while ensuring data integrity, security, and standardised information modelling. | Spec released in 2008. Wide levels of adoption in Operational Technology products and solutions. |
Functionality By the numbers
Having developed our data set of features supported by each protocol, we present some comparisons between the different protocols in various combinations.
Comparison of all 3 protocols
The following Venn diagram compares the functional overlap for the three protocols in question. The circle areas are proportional to the number of features supported.
The following aspects are worth noting:
- Lucid supports by far the most features (hence the much larger circle) – more than twice the number of each of the other protocols
- All of Sparkplug B’s features are available in Lucid (21 features)
- A large majority (21 out of 27) of OPC-UA’s features are available in Lucid. Only 6 features are unique to OPC-UA
- Only 19 out of 77 features (25%) are supported by all 3 protocols
- Lucid supports the following categories of features that the others don’t:
- Configuration of individual aspects of the device or its points, without having to reconfigure the entire device: 20 features
- Rich alarm event management: 8 features
- Onboard, user-defined logic program support: 5 features
Functionality v level of adoption
The above chart gives a stylised view of level of adoption against number of features for each protocol. Level of adoption is difficult to gauge exactly but is related to how long the protocol has been in existence. Lucid, whilst it is feature-rich, is a much newer standard than the other protocols and hence has a much lower adoption rate.
Conclusion
Whilst Lucid is the new kid on the block and therefore suffers from low adoption rates currently, it has a lot of potential as it can deliver many more features than either OPC-UA or Sparkplug-B. It may be a step too far to say it “rules them all”, but it is a promising protocol in the OT and IoT arena and certainly worthy of consideration.
Dave Howarth (NWL) and Neil Tubman (Terzo Digital)
December 2023
Please see our Lucid reading page for a collated list of other articles and information on Lucid.