Introduction to Networking: The Foundation 🌐

A deep understanding of networking is the absolute foundation for everything in cybersecurity. This document covers the core concepts.

What is a Network?

At its simplest, a network is two or more devices connected together so they can share data and resources. The entire purpose of networking is to allow devices to communicate.

Simple Analogy: A City’s Postal Service

Devices (laptop, phone) are houses.
Data is a letter.
An IP Address is your unique street address.
A MAC Address is the legal name of the person living in the house.
A Switch is the local mail carrier for your specific street (your home network).
A Router is the main post office that connects your street to the rest of the world.

The Building Blocks of a Network

All networks are made of three basic components:

Devices:
- Endpoints: Devices that people use, like computers, servers, and phones.
- Switches: A device that connects multiple endpoints on a local network (LAN).
- Routers: A device that connects different networks together.
Media: The physical or wireless connections between devices.
- Wired: Ethernet cables, fiber optic cables.
- Wireless: Wi-Fi, Bluetooth, Cellular (4G/5G).
Protocols: The sets of rules or “languages” that devices use to communicate. The most important suite of protocols is TCP/IP.

Types of Networks

Networks are categorized by their geographical size.

PAN (Personal Area Network): For one person. (e.g., connecting headphones to your phone via Bluetooth).
LAN (Local Area Network): A small, single area like a home or office. (e.g., your home Wi-Fi network).
MAN (Metropolitan Area Network): Spans a larger area like a city. (e.g., a network connecting all university campuses across a city).
WAN (Wide Area Network): The largest type, spanning countries or the globe. (e.g., The Internet).

Network Topologies

A topology is the physical or logical layout of a network.

Star Topology (Most Common): All devices connect to a central switch. It’s reliable because if one cable breaks, only one device is affected. This is the standard for modern LANs.
Bus & Ring Topologies (Historical): Older layouts that connected devices in a single line (bus) or a circle (ring). They were simple but unreliable because a single break could take down the entire network.
Mesh Topology: Devices are connected to multiple other devices. A full mesh connects every device to every other device. It’s extremely reliable but very expensive. The backbone of the Internet is a mesh network.

The Two Most Important Addresses

MAC Address (The “Who”):
- A physical, permanent, unique serial number burned into a network card. It never changes.
- Analogy: A person’s unique government ID number.
IP Address (The “Where”):
- A logical, temporary address assigned to a device on a network. It can change every time you connect.
- Analogy: The street address of the house you are currently living in. You can move houses (change IP), but your ID number (MAC address) stays the same.