IoT Protocols: How IoT Devices, Servers, and User Applications Communicate

IoT devices, servers and user applications are constantly exchanging information. They are connected to each other by networks and communicate using various data transfer protocols – something like the language that IoT equipment uses.

Let’s see what the architecture of the Internet of Things looks like and understand the means and technologies for data transmission in the IoT.

IoT Data Transfer: IoT Systems Architecture and Basic Protocols

Simply put, IoT systems are specialized networks that connect devices, gateways and data systems, where this data is then stored, processed and analyzed. Data in such a network is collected and transmitted using data transfer protocols. For communication between devices and gateways, special protocols are often used to ensure low power consumption.

The IoT network is somewhat similar to a Wi-Fi network, which connects computers in an apartment and allows you to exchange data with the Internet using a router, or to a cellular network in which cell phones are connected to towers.

Let’s take a closer look at how such a system works.

Devices collect data from users, sometimes exchange it with each other, then transmit it further, usually to gateways. Gateways are another type of device, somewhat similar to home routers, they can collect data from devices and then send it to a data center or cloud. Also, some data processing can be performed there, which allows you to save on their transfer.

There is an OSI (The Open Systems Interconnection model) model, based on which IoT protocols are divided into groups in accordance with the level of system architecture on which data will be transmitted.

OSI Model LayerFunctions
Application layerTransfer of data from devices to users. Examples of protocols: MQTT, DDS, WebSocket, AMQP, DTLS, Eddystone, HTTP, iBeacon, CoAP, PJON, STOMP, XMPP.
Presentation layerPresentation and data encryption.
Session levelSession management.
Transport levelData exchange between different architectural levels. Examples of protocols: TCP, UDP.
Network layerRoute definition and logical addressing. Examples of protocols: IPv6, IPv4, 6LoWPAN.
Data linkPhysical addressing. Examples of protocols: IEEE 802.22, LPWAN.
Physical layerWorking with the transmission medium. Bluetooth, Ethernet, LTE, NFC, RFID, Wi-Fi.

The main types of wireless networks in the IoT and data transmission standards

For the Internet of Things, technologies of wireless networks with low power consumption of different ranges are used. That is, the key factor for choosing a network connection standard will be the range of the network and how much energy it consumes.

Data transfer protocols are the backbone of any radio communication. It depends on them what network topology, routing, addressing, data security will be.

Internet of Things systems use:

Local and personal networks (WLAN – Wireless Local Area Network, and WPAN – Wireless Personal Area Network). This includes short-range (short and medium) range networks, protocols such as: Wi-Fi, 6LoWPAN, Thread, ZigBee IP, Z-Wave, ZigBee, BLE 4.2 (Bluetooth Mesh), WirelessHart, MiWi.

Energy efficient global networks (LPWAN – Low-power Wide Area Network). This includes technologies for transferring small data over long distances: LoRaWAN, SIGFOX, CIoT, 4G LTE, 5G, NB-IoT and some others.

Application protocols for data transmission in the IoT

When building IoT systems, specific protocols can be used: MQTT, AMQP, CoAP, DDS, XMPP, JMS and others, as well as protocols standard for the regular Internet, such as HTTP. The choice of the protocol depends on the problem being solved.

So, on low-power devices, they use protocols that allow you to send data with minimal power consumption, such as MQTT. If you need two-way communication with devices, protocols that allow equipment to exchange messages in real time are better suited, one of which is DDS.

That is, IoT protocols differ in their operating principles and usage scenarios.

As we already said, DDS is used for real-time systems, this is the basic model for implementing the Internet of Things, the principle of operation is based on the exchange of messages directly, and not through a server-broker.

MQTT, XMPP, AMQP, and JMS work in a different way. It is based on the idea of ​​transferring the resource-intensive part of the system to one element with a large number of resources. That is, messages are not transmitted directly, but through a broker server, which takes over all message processing. It can be deployed on a server in a data center or in the cloud.

Among protocols of this type, MQTT is gaining popularity, since it is designed specifically for the Internet of Things, does not require a permanent and stable Internet connection, and does not overload communication channels.

Another popular protocol is Modbus. It is supported by almost all industrial equipment manufacturers. Such a protocol is used for monitoring, collecting data from sensors, controlling controllers. The operating principle is based on the master-follower concept. Typically, there is only one master on the network, which forwards requests to other – slaves – devices.

CoAP is analogous to HTTP, but designed specifically for IoT equipment. The principle of operation is simple: it is focused on point-to-point (client-server) communication. The client contacts the server and sends simple commands to it, just like in HTTP.

To select the required protocol, you should focus on the number of devices, resource consumption, the amount of data transferred and the distance over which they need to be transferred.

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