IoT PROTOCOL
The Internet of Things covers a huge range of industries and use cases that scale
from a single constrained device up to massive cross-platform deployments of
embedded technologies and cloud systems connecting in real-time. The Internet of
Things is a convergence of embedded systems, wireless sensor networks, control
systems, and automation that makes connected industrial manufacturing factories,
intelligent retail, next-generation healthcare, smart homes and cities, and wearable
devices possible. A major aspect of planning an IoT technology project is to
determine the devices’ IoT protocols—in other words, how the devices connect
and communicate.
IoT devices communicate using IoT protocols. Internet protocol (IP) is a set of
rules that dictates how data gets sent to the internet. IoT protocols ensure that
information from one device or sensor gets read and understood by another device,
a gateway, a service. Different IoT protocols have been designed and optimized for
different scenarios and usage. Given the diverse array of IoT devices available,
using the right protocol in the right context is important. Some of the well-known
protocols are -
Advanced Message Queuing Protocol (AMQP)
AMQP is an open standard publish/subscribe type protocol originated in 2003
which has its roots in the financial services sector. While it has gained some
ground within the information communication technology, its use is still quite
limited in the IoT industry. The AMQP specification describes such features as
message orientation, queuing, routing (including point-to-point and
publish-and-subscribe), reliability and security. Probably the greatest benefit of
AMQP is its robust communications model. AMQP can guarantee complete
transactions — which, although useful, is not always something that the IoT
applications require.
Due to its heaviness, AMQP is not suitable for sensor devices with limited
memory, power or network bandwidth, yet for individual IoT use cases, it may be
the only protocol viable for end-to-end application, including such examples as
industrial heavy machinery or SCADA systems where the devices and the network
are considerably more capable as a rule.
Constrained Application Protocol (CoAP)
Designed to address the needs of HTTP-based IoT systems, CoAP relies on the
User Datagram Protocol (UDP) for establishing secure communication between
endpoints. By allowing for broadcasting and multicasting, UDP is able to transmit
data to multiple hosts while retaining communication speed and low bandwidth
usage, which makes it a good match for wireless networks typically employed in
resource-constrained M2M environments. Another thing that CoAP shares with
HTTP is the RESTful architecture which supports a request/response interaction
model between application endpoints. What is more, CoAP adopts the basic HTTP
get, post, put and delete methods, thanks to which ambiguity can be avoided at the
time of interaction between clients.
CoAP features Quality of Service which is used to control the messages sent and
mark them as ‘confirmable’ or ‘nonconfirmable’ accordingly which indicates
whether the recipient should return an ‘ack’ or not. Other interesting features of
CoAP are that it supports content negotiation and resource discovery mechanism.
Apart from transferring IoT data, CoAP leverages Datagram Transport Layer
Security (DTLS) for the secure exchange of messages in the transport layer. CoAP
fully addresses the needs of an extremely light protocol in order to meet the
demands of battery-operated or low-energy devices.
Message Queue Telemetry Transport (MQTT)
Probably the most widely adopted standard in the Industrial Internet of Things to
date, Message Queuing Telemetry Transport is a lightweight
publication/subscription type (pub/sub) messaging protocol. Designed for
battery-powered devices, MQTT’s architecture is simple and lightweight,
providing low power consumption for devices. Working on top of TCP/IP protocol,
it has been especially designed for unreliable communication networks in order to
respond to the problem of the growing number of small-sized cheap low-power
objects that have made their appearance in the network in the recent years.
MQTT is based on subscriber, publisher and broker model. Within the model, the
publisher’s task is to collect the data and send information to subscribers via the
mediation layer which is the broker. The role of the broker, on the other hand, is to
ensure security by cross-checking the authorisation of publishers and subscribers.
MQTT offers three modes of achieving this (Quality of Service), thanks to which
the publisher has the possibility to define the quality of its message:
■ QoS0 (At most once): The least reliable mode but also the fastest. The
publication is sent but confirmation is not received.
■ QoS1 (At least once): Ensures that the message is delivered at least once,
but duplicates may be received.
■ QoS2 (Exactly once): The most reliable mode while the most
bandwidth-consuming. Duplicates are controlled to ensure that the
message is delivered only once.
Having found wide application in such IoT devices as electric meters, vehicles,
detectors, and industrial or sanitary equipment, MQTT responds well to the
following needs:
■ Minimum bandwidth use
■ Operation over wireless networks
■ Low energy consumption
■ Good reliability if necessary
■ Little processing and memory resources
Despite its characteristics, MQTT can be problematic for some very restrictive
devices, due to the fact of the transmission of messages over TCP and managing
long topic names. This is solved with the MQTT-SN variant that uses UDP and
supports topic name indexing. However, despite its wide adoption, MQTT doesn’t
support a well-defined data representation and device management structure
model, which renders the implementation of its data management and device
management capabilities entirely platform- or vendor-specific.
Transmission Control Protocol (TCP)
The dominant protocol for a majority of internet connectivity. It offers host-to-host
communication, breaking large sets of data into individual packets and resending
and reassembling packets as needed.
User Datagram Protocol (UDP)
A communications protocol that enables process-to-process communication and
runs on top of IP. UDP improves data transfer rates over TCP and best suits
applications that require lossless data transmissions.
6LoWPAN
This IoT protocol works best with low-power devices that have limited processing
capabilities.
Near field communication (NFC)
A set of communication protocols using electromagnetic fields that allows two
devices to communicate from within four centimeters of each other. NFC-enabled
devices function as identity keycards and are commonly used for contactless
mobile payments, ticketing, and smart cards.
