Solution:

Communication layer :

• The communication layer supports the connectivity of the devices. There are multiple potential protocols for communication between the devices and the cloud.

  • The most well-known three potential protocols are,

  • HTTP/HTTPS (and RESTful approaches on those)

  • MQTT 3.1/3.1.1(Message Queuing Telemetry Transport)

  • Constrained application protocol (CoAP)

• HTTP is well known, and there are many libraries that support it. Because it is a simple text-based protocol, many small devices such as 8-bit controllers can only partially support the protocol – for example enough code to POST or GET a resource.

• The larger 32-bit-based devices can utilize full HTTP client libraries that properly implement the whole protocol.

• There are several protocols optimized for IoT use. The two best-known are MQTT6 and CoAP7.

• It has been through some iterations and the current version (3.1.1) is undergoing standardization in the OASIS MQTT Technical Committee8. MQTT is a publish-subscribe messaging system based on a broker model.

• In addition, there is an associated specification designed for ZigBee-style networks called MQTT-SN (Sensor Networks).

• CoAP is a protocol from the IETF that is designed to provide a RESTful application protocol modeled on HTTP semantics, but with a much smaller footprint and a binary rather than a text-based approach. CoAP is a more traditional client-server approach rather than a brokered approach.

• CoAP is designed to be used over UDP.

• For the reference architecture, we have opted to select MQTT as the preferred device communication protocol, with HTTP as an alternative option.