Basics of IoT Networking – Part III

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

CoAP

Introduction to Internet of Things 2

 Introduction
✓ CoAP – Constrained Application Protocol.
✓ Web transfer protocol for use with constrained nodes
and networks.
✓ Designed for Machine to Machine (M2M) applications
such as smart energy and building automation.
✓ Based on Request-Response model between end-points
✓ Client-Server interaction is asynchronous over a
datagram oriented transport protocol such as UDP
Source: Z. Shelby , K. Hartke, C. Bormann, “The Constrained Application Protocol (CoAP)”, Internet Engineering Task Force
(IETF), Standards Track, 2014

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 ✓ The Constrained Application Protocol (CoAP) is a session
layer protocol designed by IETF Constrained RESTful
Environment (CoRE) working group to provide
lightweight RESTful (HTTP) interface.
✓ Representational State Transfer (REST) is the standard
interface between HTTP client and servers.
✓ Lightweight applications such as those in IoT, could
result in significant overhead and power consumption by
REST.
✓ CoAP is designed to enable low-power sensors to use
RESTful services while meeting their power constraints.
Source: Z. Shelby , K. Hartke, C. Bormann, “The Constrained Application Protocol (CoAP)”, Internet Engineering Task Force
(IETF), Standards Track, 2014

Introduction to Internet of Things 4

 ✓ Built over UDP, instead of TCP (which is commonly used with HTTP)
and has a light mechanism to provide reliability.
✓ CoAP architecture is divided into two main sub-layers:
▪ Messaging
▪ Request/response.
✓ The messaging sub-layer is responsible for reliability and duplication
of messages, while the request/response sub-layer is responsible for
communication.
✓ CoAP has four messaging modes:
▪ Confirmable
▪ Non-confirmable
▪ Piggyback
▪ Separate
Source: V. Karagiannis, P. Chatzimisios, F. Vazquez-Gallego, and J. Alonso-Zarate, "A survey on application layer protocols for the
internet of things," Transaction on IoT and Cloud Computing, vol. 3, no. 1, pp. 11-17, 2015

Introduction to Internet of Things 5

 CoAP Position

Application

Request
CoAP
Messages

UDP

Source: Z. Shelby , K. Hartke, C. Bormann, “The Constrained Application Protocol (CoAP)”, Internet Engineering Task Force
(IETF), Standards Track, 2014

Introduction to Internet of Things 6

 CoAP Message Types

✓ Message Types-
✓ Confirmable

✓ Non-

CoAP
Confirmable

✓ Piggyback

✓ Separate
Source: Z. Shelby , K. Hartke, C. Bormann, “The Constrained Application Protocol (CoAP)”, Internet Engineering Task Force
(IETF), Standards Track, 2014

Introduction to Internet of Things 7

 CoAP Request-Response Model

Source: V. Karagiannis, P. Chatzimisios, F. Vazquez-Gallego, and J. Alonso-Zarate, "A survey on application layer protocols for the
internet of things," Transaction on IoT and Cloud Computing, vol. 3, no. 1, pp. 11-17, 2015

Introduction to Internet of Things 8

 ✓ Confirmable and non-confirmable modes represent the reliable and
unreliable transmissions, respectively, while the other modes are
used for request/response.
✓ Piggyback is used for client/server direct communication where the
server sends its response directly after receiving the message, i.e.,
within the acknowledgment message.
✓ On the other hand, the separate mode is used when the server
response comes in a message separate from the acknowledgment,
and may take some time to be sent by the server.
✓ Similar to HTTP, CoAP utilizes GET, PUT, PUSH, DELETE messages
requests to retrieve, create, update, and delete, respectively
Source: V. Karagiannis, P. Chatzimisios, F. Vazquez-Gallego, and J. Alonso-Zarate, "A survey on application layer protocols for the
internet of things," Transaction on IoT and Cloud Computing, vol. 3, no. 1, pp. 11-17, 2015

Introduction to Internet of Things 9

 CoAP Request-Response Model

Source: V. Karagiannis, P. Chatzimisios, F. Vazquez-Gallego, and J. Alonso-Zarate, "A survey on application layer protocols for the
internet of things," Transaction on IoT and Cloud Computing, vol. 3, no. 1, pp. 11-17, 2015

Introduction to Internet of Things 10

 Features
✓ Reduced overheads and parsing complexity.
✓ URL and content-type support.
✓ Support for the discovery of resources provided by
known CoAP services.
✓ Simple subscription for a resource, and resulting push
notifications.
✓ Simple caching based on maximum message age.

Source: ”Constrained Application Protocol”, Wikipedia (Online)

Introduction to Internet of Things 11

XMPP

Introduction to Internet of Things 12

 Introduction

✓ XMPP – Extensible Messaging and Presence Protocol.

✓ A communication protocol for message-oriented
middleware based on XML (Extensible Markup
Language).
✓ Real-time exchange of structured data.
✓ It is an open standard protocol.

Source: “XMPP”, Wikipedia (Online)

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 ✓ XMPP uses a client-server architecture.
✓ As the model is decentralized, no central server is required.
✓ XMPP provides for the discovery of services residing locally
or across a network, and the availability information of
these services.
✓ Well-suited for cloud computing where virtual machines,
networks, and firewalls would otherwise present obstacles to
alternative service discovery and presence-based solutions.
✓ Open means to support machine-to-machine or peer-to-peer
communications across a diverse set of networks.

Source: “XMPP”, Wikipedia (Online)

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 Highlights

✓ Decentralization – No central server; anyone can run

their own XMPP server.
✓ Open standards – No royalties or granted permissions are
required to implement these specifications
✓ Security – Authentication, encryption, etc.
✓ Flexibility – Supports interoperability

Source: “XMPP”, Wikipedia (Online)

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Source: “JabberNetwork.svg”, Wikimedia Commons (Online)

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 Core XMPP Technologies
Core
• information about the core XMPP technologies for XML streaming
Jingle
• multimedia signalling for voice, video, file transfer
Multi-user Chat
• flexible, multi-party communication
PubSub
• alerts and notifications for data syndication
BOSH
• HTTP binding for XMPP
Source: “XMPP: Technology Overview”, XMPP.org (Online)

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Weaknesses

✓ Does not support QoS.

✓ Text based communications induces higher network
overheads.
✓ Binary data must be first encoded to base64 before
transmission.

Introduction to Internet of Things 18

Applications

✓ Publish-subscribe systems
✓ Signaling for VoIP
✓ Video
✓ File transfer
✓ Gaming
✓ Internet of Things applications
▪ Smart grid
▪ Social networking services

Introduction to Internet of Things 19

 Acknowledgement
✓ "JabberNetwork.svg", Eigenes Werk, 20 July 2008, CC-BY-
SA-3.0,2.5,2.0,1.0, https://commons.wikimedia.org/
wiki/File:JabberNetwork.svg

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Thank You!!

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