Basics of IoT Networking – Part II
Dr. Sudip Misra
Associate Professor
Department of Computer Science and Engineering
IIT KHARAGPUR
Email: smisra@sit.iitkgp.ernet.in
Website: http://cse.iitkgp.ac.in/~smisra/
Introduction to Internet of Things 1
Functionality-based IoT Protocol Organization
Connectivity (6LowPAN, RPL)
Identification (EPC, uCode, IPv6, URIs)
Communication / Transport (WiFi, Bluetooth, LPWAN)
Discovery (Physical Web, mDNS, DNS‐SD)
Data Protocols (MQTT, CoAP, AMQP, Websocket, Node)
Device Management (TR‐069, OMA‐DM)
Semantic (JSON‐LD, Web Thing Model)
Multi‐layer Frameworks (Alljoyn, IoTivity, Weave, Homekit)
Source: Internet of Things Protocols (Online)
Introduction to Internet of Things 2
MQTT
Introduction to Internet of Things 3
Introduction
Message Queue Telemetry Transport.
ISO standard (ISO/IEC PRF 20922).
It is a publish‐subscribe‐based lightweight messaging protocol for
use in conjunction with the TCP/IP protocol.
MQTT was introduced by IBM in 1999 and standardized by OASIS in
2013.
Designed to provide connectivity (mostly embedded) between
applications and middle‐wares on one side and networks and
communications on the other side.
Source: “MQTT”, Wikipedia (Online)
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A message broker controls the publish‐subscribe messaging
pattern.
A topic to which a client is subscribed is updated in the form
of messages and distributed by the message broker.
Designed for:
Remote connections
Limited bandwidth
Small‐code footprint
Source: “MQTT”, Wikipedia (Online)
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MQTT Components
• Lightweight sensors
Publishers
• Applications interested in sensor data
Subscribers
• Connect publishers and subscribers
Brokers • Classify sensor data into topics
Source: “MQTT”, Wikipedia (Online)
Introduction to Internet of Things 6
MQTT Methods
Connect
Disconnect
Subscribe
Unsubscribe
Publish
Source: “MQTT”, Wikipedia (Online)
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Source: “MQTT 101 – How to Get Started with the lightweight IoT Protocol”, HiveMQ (Online)
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Communication
The protocol uses a publish/subscribe architecture (HTTP uses a
request/response paradigm).
Publish/subscribe is event‐driven and enables messages to be
pushed to clients.
The central communication point is the MQTT broker, which is in
charge of dispatching all messages between the senders and the
rightful receivers.
Each client that publishes a message to the broker, includes a topic
into the message. The topic is the routing information for the
broker.
Source: “MQTT 101 – How to Get Started with the lightweight IoT Protocol”, HiveMQ (Online)
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Each client that wants to receive messages subscribes to a
certain topic and the broker delivers all messages with the
matching topic to the client.
Therefore the clients don’t have to know each other. They
only communicate over the topic.
This architecture enables highly scalable solutions without
dependencies between the data producers and the data
consumers.
Source: “MQTT 101 – How to Get Started with the lightweight IoT Protocol”, HiveMQ (Online)
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MQTT Topics
A topic is a simple string that can have more hierarchy levels,
which are separated by a slash.
A sample topic for sending temperature data of the living
room could be house/living‐room/temperature.
On one hand the client (e.g. mobile device) can subscribe to
the exact topic or on the other hand, it can use a wildcard.
Source: “MQTT 101 – How to Get Started with the lightweight IoT Protocol”, HiveMQ (Online)
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The subscription to house/+/temperature would result in all
messages sent to the previously mentioned topic house/living‐
room/temperature, as well as any topic with an arbitrary value in
the place of living room, such as house/kitchen/temperature.
The plus sign is a single level wild card and only allows arbitrary
values for one hierarchy.
If more than one level needs to be subscribed, such as, the entire
sub‐tree, there is also a multilevel wildcard (#).
It allows to subscribe to all underlying hierarchy levels.
For example house/# is subscribing to all topics beginning with
house.
Source: “MQTT 101 – How to Get Started with the lightweight IoT Protocol”, HiveMQ (Online)
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Applications
Facebook Messenger uses MQTT for online chat.
Amazon Web Services use Amazon IoT with MQTT.
Microsoft Azure IoT Hub uses MQTT as its main protocol for
telemetry messages.
The EVRYTHNG IoT platform uses MQTT as an M2M protocol
for millions of connected products.
Adafruit launched a free MQTT cloud service for IoT
experimenters called Adafruit IO.
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SMQTT
Secure MQTT is an extension of MQTT which uses encryption
based on lightweight attribute based encryption.
The main advantage of using such encryption is the broadcast
encryption feature, in which one message is encrypted and
delivered to multiple other nodes, which is quite common in
IoT applications.
In general, the algorithm consists of four main stages: setup,
encryption, publish and decryption.
Source: M. Singh, M. Rajan, V. Shivraj, and P. Balamuralidhar, "Secure MQTT for Internet of Things (IoT)," in Fifth International Conference on
Communication Systems and Network Technologies (CSNT 2015), April 2015, pp. 746‐751
Introduction to Internet of Things 14
In the setup phase, the subscribers and publishers register
themselves to the broker and get a master secret key according to
their developer’s choice of key generation algorithm.
When the data is published, it is encrypted and published by the
broker which sends it to the subscribers, which is finally decrypted
at the subscriber end having the same master secret key.
The key generation and encryption algorithms are not standardized.
SMQTT is proposed only to enhance MQTT security features.
Source: M. Singh, M. Rajan, V. Shivraj, and P. Balamuralidhar, "Secure MQTT for Internet of Things (IoT)," in Fifth International Conference on
Communication Systems and Network Technologies (CSNT 2015), April 2015, pp. 746‐751
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