What is Computer Networking

Computer networking is the practice of connecting computing devices so they can exchange data and share resources. From the internet you use every day to the Wi-Fi in your home, networking is the invisible fabric that ties the digital world together.

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A Brief History

• 1960s — The US Department of Defense funds ARPANET, the first packet-switched network
• 1971 — Ray Tomlinson sends the first email across ARPANET
• 1973 — Vint Cerf and Bob Kahn begin designing TCP/IP
• 1983 — ARPANET migrates to TCP/IP, marking the birth of the modern Internet
• 1989 — Tim Berners-Lee proposes the World Wide Web at CERN
• 1991 — The first public website goes live
• 1995 — Commercial ISPs bring the internet to mainstream consumers
• 2007 — The iPhone launches, driving the mobile internet revolution
• Today — Over 5 billion people are connected to the internet, with billions of IoT devices joining every year

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Why Networking Matters

Networking underpins virtually every modern technology:

Domain	How Networking is Used
Cloud computing	Data centres communicate via high-speed networks
Web applications	Browsers fetch pages from servers using HTTP/HTTPS
Video streaming	Content is delivered via CDN networks globally
Online gaming	Low-latency connections keep gameplay responsive
IoT	Smart devices communicate over Wi-Fi, Bluetooth, and cellular
Remote work	VPNs and video conferencing rely on stable networks
E-commerce	Secure transactions depend on encrypted network protocols

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Types of Networks

Networks are classified by their size and scope:

Type	Full Name	Description	Example
PAN	Personal Area Network	Connects devices within a few metres	Bluetooth headset to phone
LAN	Local Area Network	Connects devices in a building or campus	Office Wi-Fi network
MAN	Metropolitan Area Network	Spans a city or large campus	City-wide fibre backbone
WAN	Wide Area Network	Spans countries or continents	The Internet itself
WLAN	Wireless LAN	A LAN using wireless technology	Home Wi-Fi network

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Network Topologies

The topology describes how devices are arranged and connected:

Common Topologies

Topology	Description	Pros	Cons
Star	All devices connect to a central switch/hub	Easy to manage, one failure does not affect others	Central device is a single point of failure
Bus	All devices share a single communication line	Simple and cheap	Hard to troubleshoot, one break takes down the segment
Ring	Devices form a circular chain	Predictable performance	One device failure can disrupt the ring
Mesh	Every device connects to every other device	Highly redundant and fault-tolerant	Expensive and complex
Hybrid	Combination of topologies	Flexible	Can be complex to design

Most modern networks use a star or hybrid topology.

Star Topology:

      [PC1]   [PC2]
         \     /
         [Switch]
         /     \
      [PC3]   [PC4]

Mesh Topology:

      [A]------[B]
      | \    / |
      |   \/   |
      |   /\   |
      | /    \ |
      [C]------[D]

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Key Networking Concepts

Clients and Servers

• A client initiates a request (e.g., your web browser)
• A server responds to the request (e.g., a web server hosting a site)
• Most internet communication follows this client-server model

Packets

Data is not sent as one continuous stream. Instead, it is broken into small units called packets:

• Each packet contains a header (source, destination, sequence number) and a payload (the actual data)
• Packets may take different routes to the destination
• The receiving device reassembles them in the correct order

Bandwidth vs Latency

Term	Definition	Analogy
Bandwidth	The maximum amount of data that can be transmitted per second	Width of a motorway
Latency	The time it takes for a packet to travel from source to destination	Speed limit on the motorway
Throughput	The actual data transfer rate achieved	Actual traffic flow

Example: A 100 Mbps connection (bandwidth) with 20 ms latency means you can transfer up to 100 megabits per second, but each individual packet takes at least 20 milliseconds to arrive.

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Protocols — The Language of Networks

A protocol is a set of rules that governs how data is transmitted and received. Without protocols, devices would not understand each other.

Protocol	Purpose
TCP	Reliable, ordered delivery of data
UDP	Fast, connectionless delivery (no guarantee)
IP	Addressing and routing packets across networks
HTTP/HTTPS	Web page requests and responses
DNS	Translating domain names to IP addresses
DHCP	Automatically assigning IP addresses to devices
FTP	File transfers
SSH	Secure remote shell access

We will explore each of these protocols in detail throughout this course.

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Network Models

To manage the complexity of networking, engineers use layered models that separate concerns into distinct layers:

The Two Major Models

Model	Layers	Purpose
OSI Model	7 layers	A theoretical reference model for understanding networking
TCP/IP Model	4 layers	The practical model used by the Internet

OSI Model             TCP/IP Model
┌─────────────┐
│ Application │
├─────────────┤       ┌─────────────┐
│ Presentation│       │ Application │
├─────────────┤       ├─────────────┤
│  Session    │       │  Transport  │
├─────────────┤       ├─────────────┤
│  Transport  │       │  Internet   │
├─────────────┤       ├─────────────┤
│  Network    │       │  Network    │
├─────────────┤       │  Access     │
│  Data Link  │       └─────────────┘
├─────────────┤
│  Physical   │
└─────────────┘

We will cover these models in depth in the next two lessons.

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Summary

Computer networking is the foundation of our connected world. It involves connecting devices so they can exchange data using agreed-upon protocols. Networks vary in size from PANs to WANs, can be arranged in different topologies, and rely on layered models (OSI and TCP/IP) to organise the complexity. In the following lessons, we will dive into the OSI model, TCP/IP, IP addressing, DNS, HTTP, routing, network devices, troubleshooting, and cloud networking.