Networking Fundamentals: Practical Look at the OSI Model

Introduction

• The lesson is part of a course on networking fundamentals.
• Focus on the OSI model, a set of rules divided into seven layers allowing hosts to share data.
• Networking automates data sharing between hosts.

OSI Model Overview

• Networking has its own rules like languages (English, Spanish, etc.).
• The OSI model consists of seven layers.
• Each layer has a specific function contributing to the overall goal of data sharing.

Layer 1: Physical Layer

• Purpose: Transporting bits (ones and zeros).
• Technologies: Cables, Wi-Fi.
  • Move bits from one end to another.
• Devices: Repeaters, Multi-port Repeaters (Hubs).
  • Extend signals, considered Layer 1 technologies.

Layer 2: Data Link Layer

• Interaction with Physical Layer: Puts and retrieves bits on/from the wire.
• Key Concepts:
  • NIC (Network Interface Card): Connects to PC for data transfer.
  • Wi-Fi Access Card: Interacts with Wi-Fi radio waves.
• Goal: Hop-to-hop delivery.
  • Uses MAC Address (48 bits, 12 hex digits).
  • Unique to each NIC.
  • Addresses formatted differently across systems (Windows, Linux, Cisco).
• Devices: Switches.
  • Facilitate communication within a network.

Layer 3: Network Layer

• Goal: End-to-end delivery.
• Addressing Scheme: IP Addresses (32 bits, four octets).
  • Identify hosts for data transfer.
• Devices: Routers.
  • Facilitate multi-hop communication.
• Question: Why both MAC and IP addresses?
  • Serve different purposes: MAC for hop-to-hop, IP for end-to-end.

How Data Flows Through the Network

• Data is a set of ones and zeros needing to reach a destination.
• Layer 3 Information: Source and destination IP addresses.
• Layer 2 Information: Source and destination MAC addresses for each hop.
• Data moves hop-by-hop via Layer 2, end-to-end via Layer 3.

Address Resolution Protocol (ARP)

• Links Layer 3 (IP) to Layer 2 (MAC) addresses.
• Crucial for understanding data flow in a network.

Conclusion of Part 1

• Discussed Layers 1, 2, and 3 of the OSI Model.
• Explained how layers contribute to data flow through a network.
• Next part will discuss the transport layer.

Additional Notes

• Feedback and suggestions for the course are encouraged.
• Course aims to be the ultimate guide to networking fundamentals.
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