Describing a short overview for understanding MQTT protocol

1. A short report on MQTT protocol for Internet of Things (IoT)
To
Dr. Nawaporn Wisitpongphan
By
Md.Bayazid Bostame
Student ID: 5909103860046
Thai-German Graduate School of Engineering
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1.1 Introduction
With the ongoing development of the social economy and tremendous development of technology
a large number of home appliances and industrial appliances have been presented into our day to
day lives which need to be accessed through internet. Now-a-days we can see a lot of smart devices
which are used in our everyday life. The ideas of smart home and smart industry are gaining
importance in the present context due to their ability to automate industrial and home environments
with great effectiveness. Smart systems are defined as miniaturized devices that incorporate
functions of sensing, actuation and control. For this ongoing development Internet of Things (IoT)
has become a must for maintaining the smart devices to ensure correctness and effectiveness.
Internet of Things (IoT) is a term which is used to describe the practice of connecting devices
through the use of the Internet. From the report published in international journals it is seen that
the number of connected devices is forecasted to more or less 30 billion 2020. For this increasing
number of connected devices IoT need a protocol by which the connected devices may
communicate when required. This report shows the feature of MQTT which supports the necessity
of IoT. MQTT stands for Message Queuing Telemetry Transport which is functioned as
publish/subscribe, is an extremely simple and lightweight messaging protocol, designed for
constrained devices and low-bandwidth, high-latency or unreliable networks.
1.2 Overview
MQTT is a very light weight protocol designed for IoT which supports lots of features with
consistent accuracy. It might be a question why we need MQTT protocol when HTTP is still exists
and working fine. The clarification of that question is that HTTP is great for doing request and
response like a client may ask for information to a server and server will response according to
that request but it doesn’t really have a good solution when a source of information should push a
change to many clients and there is no built in support for quality of service. The text based format
of HTTP requires more bandwidth and any device that act as host must have a server installed and
keep the server live to answer incoming request consumes a lot of battery life but MQTT solves
many of the problems of HTTP. First of all it introduce a publish and subscribe messaging pattern
which means that any source of information such as a sensor can publish its data and then any
client can subscribe that data. All these is happening in a broker like keep track of all subscription
and publications so when a publisher sense and update with new data it publishes a message and
the broker takes care of sending the new data to all subscriber. The built in support for quality of

2. services meaning that the broker can guarantee the delivery of the message e.g. that is delivered at
least one time or exactly once. MQTT is a binary format that requires a minimum bandwidth. The
fixed header is actually only 2 bytes and it also has a small implementation footprint that requires
less battery. So it may said that MQTT can handle smaller devices in low bandwidth because
MQTT control packet headers are kept as small as possible. Each MQTT control packet consist of
three parts, a fixed header, variable header and payload. MQTT has a small header overload that
makes it appropriate for IoT by lowering the amount of data transmitted over week network .Both
of these efficient aspects make MQTT scale very well and it is very important when we handle a
million of devices.
1.3 MQTT Functionality
So as explained MQTT is a connectivity protocol designed for M2M. It is an extremely lightweight
publish/subscribe messaging transport that is ideal for connecting small devices connected on
networks with minimal bandwidth. Now I want to explain how actually it works. Below is a simple
figure of how it works. So it follows publish/subscribe messaging protocol which allows a message
to be published once and multiple subscribers to receive the message providing decoupling
between the publisher and subscriber. A publisher publish a message (Publication) in the Topics.
Figure: Simple MQTT functions
Publisher Topics
Subscriber
Subscriber
Subscriber
Message
A
Message
A
Message
A
Message
A

3. The subscribers subscribe to the Topics for message (publications). A message server or Broker
matches publications to subscriptions. If it found no matches the message will be discarded. If one
or more matches the message the broker will deliver the message to each subscriber. Thus it works.
Now come to the technical mechanism. The MQTT messages are delivered asynchronously
(“PUSH”) through publish subscribe architecture. It works by exchanging some set of control
packets where each control packets has a specific functions. The MQTT topology has a MQTT
server and MQTT client and they are communicate by those control packets. Every steps of
communication has a verification e.g. CONNECT packet is responsible to send the request to the
server informing that client wants to connect and CONNACK packet is generated by the server to
acknowledge the client about the connections. Similarly PUBLISH and PUBACK packet work
like same process.
1.4 Security of MQTT
MQTT provides security in multiple layers. Each layer prevents different kind of attacks. The goal
of the protocol is to provide a really lightweight and easy to use communication protocol for the
IoT and because of that the protocol specified a few security mechanism. It provides security like
SSL/TLS for transport security.
1.5 Goals
MQTT (Message Queuing Telemetry Transport) is one of the protocols supported by the IBM
Message Broker products as a communicating data to and from the Broker. The protocol was
designed specifically for remote telemetry applications, with three specific design goals:
1. The protocol should be as lightweight as possible across the "wire" (or other
communication medium) most remote telemetry is done over low bandwidth, high cost
networks, and so minimizing the overhead of each message is highly desirable.
2. The protocol should be very easy to implement on embedded devices such as sensors and
gateways.
3. Can handle lots of devices whether it is a lower configured device or higher and with a
minimum bandwidth.
4. This protocol maintains consistency to lower latency.
1.6 Conclusion
MQTT provides a lots of functions for the Internet of Things. It can help providing a great
performance and create new area for messaging and can handle billion of things connected through
the internet. It is a very light weight protocol that can work with every types of devices and work
using a minimum bandwidth. Now-a-days facebook.com is using MQTT protocol for their
messenger which working great in our messaging in social network.