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Key Concepts

IoT Networking and Data Standards

https://networklessons.com/cisco/evolving-technologies/iot-standards-and-protocols

There are many protocols that have a direct or indirect role in IoT. We’ll focus on two protocol types in particular:

• Network protocols
• Data protocols

Network Protocols

The network protocols we use for IoT should be open standards because our IoT network has to support devices from multiple vendors. Proprietary protocols increase complexity because you then need devices that can translate between the different protocols.

The Internet Protocol (IP) is well established and we have been using IP for IT networks for a long time. This is one of the reasons why IP is also the main choice for IoT networks.

Using IPv6 is encouraged because there are no address space limitations as there are with IPv4. Solutions such as IPv6 over Low-Power Wireless Personal Area Networks (6LoWPAN) or IPv6 Routing Protocol for LLNs (RPL) don’t even support IPv4, only IPv6.

Data Protocols

We need to transfer data between our devices and other systems such as an IoT platform. Some devices have sensors that push data at a regular interval. Other sensors work with a pull model where you have to request the information. There are several data protocols we can use in IoT. Here are three popular protocols:

• Message Queuing Telemetry Transport (MQTT)
• Constrained Application Protocol (CoAP)
• Extensible Message and Presence Protocol (XMPP)

MQTT

MQTT is probably the most used protocol in IoT. It’s a lightweight message protocol that uses publish and subscribe operations to transmit data between a client and server. It uses TCP as the transport protocol.

Packets are tiny and require little bandwidth. MQTT uses a client-server model. The server is called a broker. There are two operations:

• Publish: a device (client) sends data to a broker (server).
• Subscribe: a device (client) wants to receive data from a broker (server).

CoAP

CoAP is also a lightweight protocol and was developed as a standard (RFC 7252). It’s based on a REST model. A server makes resources available under a URL and clients access these resources with GET, PUT, POST, and DELETE methods. It is easy to get started with CoAP because many developers are familiar with REST.

CoAP can carry different payload types including XML and JSON and uses UDP as the transport protocol.

XMPP

XMPP is an open standard (RFC6120) and is based on XML technology for real-time communication. It’s used for a range of applications including VoIP, instant messaging, and IoT.

XMPP has been around for a while and has proven scalability and security. There are many servers that have used XMPP for many years. Software is available for any programming language making it easy to get started. Because XMPP was originally an instant messaging protocol and uses XML, it has more overhead compared to a lightweight protocol like MQTT.

OpenDDS concepts

https://objectcomputing.com/products/opendds

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