648  Layered Models: Fundamentals

648.1 Overview

Layered network models are the foundation of all IoT communication. This section covers the theoretical frameworks (OSI, TCP/IP) and IoT-specific reference models that enable billions of devices to communicate seamlessly.

TipMVU: Minimum Viable Understanding

Core concept: Network communication is organized into layers (OSI: 7 layers, TCP/IP: 4 layers) where each layer handles one specific function and adds its own header to data passing through - a process called encapsulation.

Why it matters: When IoT connectivity fails, understanding layers helps you diagnose whether the problem is physical (antenna/cable), network (IP/routing), or application (code/protocol) - each requires different troubleshooting.

Key takeaway: Think โ€œbottom-upโ€ when debugging: check Physical layer first (is the device powered and connected?), then Data Link (MAC address visible?), then Network (IP assigned?), and finally Application (service running?).

648.2 Learning Objectives

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

  • Understand Network Standards: Explain why standards and protocols enable global connectivity
  • Compare OSI and TCP/IP Models: Differentiate between the seven-layer OSI and four-layer TCP/IP models
  • Explain Encapsulation: Describe how data moves through protocol layers
  • Apply IoT Reference Models: Understand IoT-specific architectural frameworks
  • Configure MAC and IP Addressing: Work with hardware and network layer addresses

648.3 Chapters in This Section

648.3.1 OSI and TCP/IP Models

The foundational layered network models that enable global interoperability.

Topics covered: - Networking standards organizations (IEEE, IETF, ITU, ISO) - What is a protocol and why we need them - The OSI 7-layer theoretical framework - The TCP/IP 4-layer practical implementation - Layer-by-layer troubleshooting approach

Key figures:

OSI 7-layer reference model showing Application, Presentation, Session, Transport, Network, Data Link, and Physical layers with descriptions of each layer's function and example protocols

OSI Model - Standard quality PNG format

OSI 7-layer reference model showing Application, Presentation, Session, Transport, Network, Data Link, and Physical layers with descriptions of each layer's function and example protocols - scalable vector format

OSI Model - Scalable SVG format for high resolution
Figure 648.1: OSI 7-layer reference model for network communication

648.3.2 Encapsulation and Protocol Data Units

How data is transformed as it moves through protocol layers.

Topics covered: - Protocol Data Units (PDUs) at each layer - Encapsulation: headers added going down - Decapsulation: headers removed going up - Byte-level analysis of protocol overhead - Why IoT uses header compression

Key figures:

Encapsulation and decapsulation
Figure 648.2: Encapsulation and decapsulation process through OSI/TCP-IP layers
Protocol Data Units
Figure 648.3: Protocol Data Units (PDUs) at each network layer - frames, packets, segments, data

648.3.3 IoT Reference Models

IoT-specific architectural frameworks beyond traditional networking.

Topics covered: - Why IoT needs specialized reference models - ITU IoT Reference Model (4 layers + cross-cutting) - Cisco 7-Level IoT Reference Model (detailed) - Comparing Wi-Fi, Zigbee, and LoRaWAN stacks - Edge computing: where to process data

Key figures:

Comprehensive 7-level IoT reference model from bottom to top: Physical Devices and Controllers, Connectivity, Edge Computing, Data Accumulation, Data Abstraction, Application, and Collaboration and Processes layers

7-level IoT reference model

Comprehensive 7-level IoT reference model from bottom to top: Physical Devices and Controllers, Connectivity, Edge Computing, Data Accumulation, Data Abstraction, Application, and Collaboration and Processes layers - scalable vector format

7-level IoT reference model
Figure 648.4: 7-level Internet of Things reference model showing complete IoT stack

648.4 Quick Reference

Model Layers Use Case
OSI 7 (Application to Physical) Teaching, troubleshooting, detailed analysis
TCP/IP 4 (Application to Network Access) Practical implementation, development
ITU IoT 4 + cross-cutting Standards compliance, architecture planning
Cisco 7-Level 7 (Devices to Collaboration) IoT system design, edge computing decisions

648.5 Whatโ€™s Next

Start with the foundational models, then progress through practical implementation:

  1. OSI and TCP/IP Models - Start here to understand the layered model foundation
  2. Encapsulation and Protocol Data Units - Learn how data moves through layers
  3. IoT Reference Models - Explore IoT-specific architectures
  4. Layered Models: Labs and Implementation - Hands-on MAC/IP addressing and Python implementations
  5. Layered Models: Review - Test your understanding with comprehensive knowledge checks

IoT Reference Architectures: - IoT Reference Models - Multi-layer IoT system architectures - Architectural Enablers - Technologies enabling IoT at each layer

Protocol Stack Components: - IoT Protocols Fundamentals - How IoT protocols fit into layered models - Networking Fundamentals - Core networking principles across layers - Application Protocols - Application layer protocols (MQTT, CoAP, HTTP)

Addressing: - Networking Addressing and Subnetting - IP addressing, subnet masks, CIDR