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An IoT protocol is a method of communication between the device and the network. In essence, it’s the road or highway the data must travel to get from place to place. 

Many IoT devices use internet protocols (IP) to connect, but others utilize other methods such as Bluetooth or cellular. Because so much of the buzz around IoT centers on end devices and cloud-based platforms designed to wrangle data, many people forget that IoT protocols and standards are essential pieces of the puzzle — they pave the way for data to flow from device to gateway to cloud. 

Why are IoT protocols so important? 

Short answer: They enable efficient, structured communication between IoT hardware. Let’s take a look at a few key reasons why IoT protocols are important:

  1. They enable the exchange of information between hardware (without them, no IoT device would work). It would be like owning a nice sports car with no road to drive it on.

  2. They also create a structure or language that makes information exchanges more efficient and comprehensible. The better the protocol, the more efficient the processing and transfer speeds.

  3. For devices with lower computer power, they are far more efficient than using the regular internet, which was designed for computers, not IoT sensors. Data protocols like the Constrained Application Protocol (CoAP) were designed to compress HTTP (normal internet protocol) into a device-friendly version.

Recommended reading: What is IPsec? Internet Protocol Security and Cellular IoT

What protocols do IoT-qualified devices use?

IoT protocols fall into one of two main categories:

Data protocols

IoT data protocols allow point-to-point connectivity between devices, even if there is no internet connection available. Similar to how a walkie-talkie operates, typically only two devices are communicating with one another. 

Network protocols

IoT network protocols allow devices to connect to one another and to the internet. They also allow connections to form between multiple devices at once.

How are they used?

IoT network protocols are connected to the internet and networks, but when they’re running on IoT devices, they can prove too much for the limited computing power of many sensors, causing slowdowns. IoT data protocols are very efficient on end devices but can only be used between small networks, and sometimes only two devices (depending on the protocol). 

IoT data protocols

Now, let’s take a closer look at some of the IoT data protocols in use today.

Message Queuing Telemetry Transport (MQTT)

Perhaps the most common IoT data protocol, MQTT is actually a subscription-based service. Designed to be used in inexpensive, battery-powered IoT sensors, MQTT’s basic architecture limits power usage and is only able to send small amounts of data. It is built using the code for Transmission Control Protocol (TCP), which means it uses wireless networks rather than the internet.

MQTT uses the subscriber, publisher, and broker model. Here’s how it works: The “publisher” collects the data from the devices and sends the data through the “broker,” who checks authentication on both ends to enhance security. They then send the data to the “subscriber” — the person (or computer) using the device.

Common use cases for MQTT include smart utility meters, sensors used in smart cities and agriculture, and connected machinery in smart factories and IIoT settings. Basically, any IoT device that’s small, sends data intermittently, and is deployed in remote locations is a good candidate for MQTT’s minimalist approach.

Constrained Application Protocol (CoAP)

Designed for constrained networks and nodes in IoT devices, CoAP compresses data sufficiently to support a limited network of devices, but not the actual internet. It’s an application layer protocol that translates the Hypertext Transfer Protocol (HTTP), making it accessible for use in more restrictive networks and devices. To achieve this, CoAP uses the User Datagram Protocol (UDP) to create a secure link between endpoints. While maintaining low bandwidth and a steady flow of communication, UDP can enable multiple hosts to exchange data. To ensure secure communications, CoAP uses Datagram Transport Layer Security (DTLS). 

Recommended reading: User Datagram Protocol: What Role Does UDP Play in Cellular IoT?

Advanced Message Queuing Protocol (AMQP)

An open standard protocol, AMQP falls under the publish/subscribe protocol type and originated in the financial sector in the early 2000s. Its adoption in the IoT world is still minimal, but it offers a strong and multi-faceted communications model with queuing, routing, and message orientation features. AMQP uses more data and bandwidth than MQTT and CoAP, making it unsuitable for low-power IoT devices and edge sensors. Its main distinction is allowing connection to the cloud while still maintaining efficiency and high levels of security. As a result, AMQP is a good fit for end-to-end applications in IIoT (heavy machinery or SCADA/automation control systems, for example) while it continues to be used in banking.

Data Distribution Service (DDS) 

Created with publish-subscribe methodology, the DDS protocol standardizes real-time communication between devices to ensure dependable, scalable, and high performance communication that’s not reliant on hardware and software platforms. A key aspect of this protocol is that while data appears to remain local, it is actually being stored on remote nodes. DDS is the first open international middleware IoT standard, and finds many potential applications including smart utilities, public transportation systems, healthcare, autonomous vehicles, and robotics.

WebSocket

Created as part of the HTML5 initiative in 2011, the WebSocket protocol allows two nodes to both send and receive data simultaneously using a single TCP connection. Normally, a device sends data, has an authentication “handshake” with the receiver, and sends its data before allowing the receiver to send data, continuing a back and forth “conversation” between the two endpoints. WebSocket abridges that method and lets both parties “talk” at the same time. This makes WebSocket extremely useful for situations such as stock trading, where very rapid data exchanges are required. The downside is that it ties up more bandwidth while the conversation is happening.

Machine to Machine Protocol (M2M)

M2M is an open industry protocol that was created with IoT applications in mind. It’s primarily used for letting two machines communicate with one another in an extremely efficient way — particularly useful with machines that self-monitor their operation depending on the status of the other machine. For example, one machine on an assembly line might tell another device that it’s running low on a component produced by the other and request more of that component. M2M is often used in smart vehicles, IIoT, smart homes, vending machines, and ATM machines. 

Network protocols for IoT

Here’s a closer look at some of the IoT network protocols in use today.

HyperText Transfer Protocol (HTTP) 

A protocol at the application layer, HTTP is the foundation of the internet as we know it. HTTP undergirds data communication on the World Wide Web, enabling web links from page to page. As mentioned previously, it’s a poor protocol choice for most IoT devices due to the amount of power it needs and the data it consumes. There are some exceptions, though — for example, devices that need to transfer copious amounts of data, such as 3D printers, benefit from using HTTP.

Wi-Fi

Wi-Fi is widely used in some IoT end devices, particularly consumer and smart home devices and others that are expected to stay within range of a router. It’s not a useful protocol for remote IoT applications like smart agriculture and utilities, and not chosen often for such use cases because of its limited range and scalability, and high power consumption. Security is also a concern with Wi-Fi, as data is often transmitted without encryption and subject to backdoor hackers. Recently, Wi-Fi HaLow has been developed for IoT, offering a wider transmission range and less power consumption — but it still carries potential security vulnerabilities.

Recommended reading: Where Do Internet of Things Security Vulnerabilities Really Come From?

Bluetooth

A 2.4 GHz network that provides low energy use and a good range, Bluetooth is a relatively inexpensive and practical choice for some IoT applications. Compared to the wider range of cellular and some other protocols, though, it cannot quite compete. Bluetooth Low Energy (BLE) has become a popular choice for many IoT use cases, including healthcare devices, that use hub devices as intermediaries to connect to the cloud. In these cases, the edge device (a health monitor, for example) uses Bluetooth to connect to the hub device (a smartphone), which then links to the cloud via a Wi-Fi or cellular connection.

Lightweight M2M (LWM2M)

LWM2M is a type of M2M protocol that has greater capacity for sensor networks while still maintaining very low data demands (and fast speeds). It’s distinguished by four major interfaces other protocols do not have:

Bootstrapping interface

This means that you can configure a device remotely without needing to preconfigure it at the factory.

Client registration interface 

The client registration interface notifies the server of the client’s presence and which functions it supports. Additionally, it provides a delivery route for over-the-air (OTA) updates for firmware and software.

Device management and service enablement interface 

With this interface, the provider can remotely alter device settings and parameters.

Information reporting interface

With this interface, the user can access information about how the system is working remotely.

Because LWM2M was designed with IoT device management and telemetry in mind, it’s a great fit for many low-power edge devices such as IIoT sensors, smart meters, and smart building sensors.

XMPP 

XMPP stands for “Extensible Messaging Presence Protocol” and was developed in the open source community nearly two decades ago for use in human-to-human real-time messaging (to use a current example, the instant message application WhatsApp). Today, XMPP is useful for M2M communications in some use cases, especially consumer IoT applications like smart appliances, where human end users might need to communicate with human technicians. It is fairly customizable, and remains an open source protocol that the XMPP Standards Foundation supports.

Cellular 

Most people are familiar with the basic cellular network standards — 2G, 3G, 4G LTE, and now 5G. While developed for use with consumer cellular telephones, cellular has been adapted for IoT use and is among the best options for many use cases, especially when devices are deployed in remote areas. Cellular connectivity offers excellent security with end-to-end data encryption and, depending on the network, can handle high bandwidth data transfers. To accommodate low-power IoT devices and massive deployments, alternate LTE IoT standards such as Narrowband IoT (NB-IoT), Cat-1, and Cat-M1 have emerged, providing better long-range coverage at lower costs.

Recommended reading: NB-IoT and Cat-M1 vs. Cat-1: How to Choose the Right LTE IoT Standard

ZigBee 

ZigBee is designed to allow smart devices to work together to complete a task. Its defining marks are low power consumption and throughputs and a wide connectivity range of around 100 meters. It’s common in IIoT settings, alarm and monitoring systems, smart meters, and telemetry systems. Automated street lights in cities as well as some smart home devices also use this protocol, which can support 65,000 devices in a single network.

Z-Wave 

Very similar to ZigBee, Z-Wave is designed for use on a smaller scale as it caps out at 232 devices per network. It provides encryption, lending a greater level of data security, and is a proprietary technology supported by the Z-Wave Alliance. Because it operates on a distinctive radio wavelength (800-900 MHz), Z-Wave avoids interference problems, helping to ensure that devices stay connected. Like ZigBee, it’s currently more popular for consumer IoT applications than industrial use cases, although it’s used in some energy management applications.

Long Range Wide Area Network (LoRaWan)

LoRa, which stands for “long range,” was developed by the LoRa Alliance, with Semtech as a founding member. The Alliance governs the proprietary LoRa technology, now including LoRaWAN, an open cloud-based protocol that lets IoT devices communicate using LoRa technology. LoRaWAN can support millions of devices, making it an excellent choice for smart cities and other massive IoT applications.

What’s the best IoT protocol? 

That’s a bit like asking, “What is the best car?” The answer depends on what you need it for. 

If your IoT use case requires incredibly fast communication but sends minimal amounts of data, WebSocket might be a good fit. If you’re deploying thousands of tiny low-power IoT devices in an underground mining operation, a protocol that supports LPWAN is going to work best — cellular IoT standards like NB-IoT or Cat-M1, for example. If you need to transfer huge amounts of data, stick with HTTP. Each protocol has a niche where it excels, and other areas of weakness.

Conclusion

IoT protocols are the languages that enable devices and networks to communicate with one another. Standardized protocols are essential components for the Internet of Things, allowing structured communication while minimizing security vulnerabilities. Still, with so many different IoT protocols in use — including both open source and proprietary options — some experts argue for the development of a global standard to regulate all IoT devices and connections. While no one has stepped up to create such a universal standard to date, recent protocols designed with IoT in mind are taking up the challenge and offering a combination of simple structure, speed, and security measures — LwM2M, for example. 

But in reality, the world of IoT continues to be variable and fragmented, with as much diversity in connective technologies as it has in types of devices and use cases. Perhaps it will continue to work best for IoT device designers to have a library of different protocols to choose from.

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