1167  IoT Application Protocols Overview

1167.1 Learning Objectives

By the end of this module, you will be able to:

  • Understand Application Layer Protocols: Explain the role of application protocols in IoT
  • Compare Traditional vs IoT Protocols: Differentiate between HTTP/XMPP and lightweight IoT protocols
  • Choose Appropriate Protocols: Select between CoAP and MQTT based on application requirements
  • Analyze Protocol Trade-offs: Evaluate connection models, transport layers, and overhead
  • Design IoT Communication: Apply protocol selection principles to real-world scenarios
  • Understand Real-time Protocols: Explain VoIP/SIP/RTP architecture for audio/video IoT applications

1167.2 Module Overview

This module covers IoT application layer protocols - the languages devices speak to exchange data. The content has been organized into focused chapters for easier learning:

1167.2.1 Chapter Guide

Chapter Topics Covered Estimated Time
Introduction and Fundamentals Protocol basics, MQTT vs CoAP overview, beginner concepts, interactive comparison tool 10-15 min
CoAP vs MQTT Comparison Detailed protocol comparison, architecture, QoS, security, resource usage, selection framework 15-20 min
HTTP and Modern Protocols Module index for HTTP in IoT 5 min
- HTTP Pitfalls and Connection Management Polling battery drain, TLS overhead, WebSocket management, payload protection 15-20 min
- HTTP/2 and HTTP/3 for IoT Multiplexing, HPACK compression, QUIC transport, 0-RTT, protocol selection 15-20 min
API Design Best Practices REST API design, topic naming, payload formats, versioning, rate limiting, security 15-20 min
Real-Time Protocols VoIP, SIP, RTP for video doorbells, baby monitors, intercoms, security cameras 10-15 min

Total Module Time: ~65-90 minutes

1167.3 Quick Protocol Reference

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graph TB
    subgraph Protocols["IoT Application Protocols"]
        MQTT["MQTT<br/>Publish-Subscribe<br/>TCP, QoS 0/1/2"]
        CoAP["CoAP<br/>Request-Response<br/>UDP, RESTful"]
        HTTP["HTTP/REST<br/>Universal<br/>TCP, Heavy headers"]
        RTP["RTP/SIP<br/>Real-time media<br/>UDP, Low latency"]
    end

    subgraph UseCases["Best For"]
        M_UC["Telemetry, dashboards<br/>Event-driven systems"]
        C_UC["Battery sensors<br/>Direct device control"]
        H_UC["Gateways, web apps<br/>Cloud integration"]
        R_UC["Video doorbells<br/>Voice assistants"]
    end

    MQTT --> M_UC
    CoAP --> C_UC
    HTTP --> H_UC
    RTP --> R_UC

    style MQTT fill:#E67E22,stroke:#D35400,color:#fff
    style CoAP fill:#16A085,stroke:#16A085,color:#fff
    style HTTP fill:#3498db,stroke:#2980b9,color:#fff
    style RTP fill:#9b59b6,stroke:#8e44ad,color:#fff

Figure 1167.1: Quick reference for IoT application protocol selection
Protocol Pattern Transport Overhead Best For
MQTT Publish-Subscribe TCP 2-byte header Event streams, telemetry, cloud
CoAP Request-Response UDP 4-byte header Battery sensors, direct queries
HTTP Request-Response TCP 100+ bytes Gateways, web integration
RTP/SIP Session streams UDP 12-byte header Audio/video, doorbells

1167.4 Start Learning

Recommended path for beginners: 1. Start with Introduction and Fundamentals 2. Continue to CoAP vs MQTT Comparison 3. Then explore specialized topics as needed

For experienced developers: - Jump directly to API Design Best Practices - Or HTTP and Modern Protocols for HTTP/2/3 deep dive

1167.5 Key Concepts Summary

MQTT (Message Queue Telemetry Transport) - Publish-subscribe pattern with central broker - TCP transport with QoS levels (0, 1, 2) - Best for: many devices β†’ cloud, event-driven systems

CoAP (Constrained Application Protocol) - RESTful (GET/PUT/POST/DELETE) over UDP - Connectionless, minimal overhead - Best for: battery sensors, direct device control

HTTP/REST - Universal compatibility, rich tooling - High overhead for constrained devices - Best for: gateways, cloud APIs, web integration

VoIP/RTP/SIP - Real-time audio/video streaming - Session-based with sub-150ms latency - Best for: video doorbells, baby monitors, intercoms

1167.6 What’s Next?

Begin with Introduction and Fundamentals to understand the basics of IoT application protocols.

After completing this module, continue to: - MQTT Fundamentals for deep dive into MQTT - CoAP Fundamentals and Architecture for CoAP details