The internet is basically a giant system that lets computers talk to each other. It didn't come from magic; it's just a bunch of smart solutions to simple problems.
Step 1: Sharing Information
Problem: I have a file on my computer, you want it on yours.
Primitive method: I give you a USB. Works, but very slow.
Better method: Connect computers with a cable and send 0s and 1s as signals.
This creates a direct link between two computers.
Step 2: Many Computers Talking
With only 2 computers, 1 cable works.
With 100 computers, we'd need thousands of cables → impossible.
Solution: A Switch.
Everyone connects to the switch.
Switch decides who gets the message.
This is a Local Network (LAN).
Step 3: Connecting Multiple Networks
One office has its LAN, another office has their LAN.
How do these two LANs talk?
Solution:Router.
Special device that connects one network to another.
It forwards messages to the right destination.
Internet = a network of networks linked by routers.
Step 4: Finding the Right Computer
Millions of computers online. How do you know which one to reach?
Solution: IP Address = digital street address.
Example: 142.250.72.206 (one of Google's IPs).
Every device has a unique address on the internet.
Routers look at the address and pass the message step by step until it reaches the destination.
Step 5: Sending Large Files Safely
Imagine sending one huge movie in one piece:
It would block the network for others.
If a single bit gets corrupted, you'd need to resend the entire file.
Solution: Break it into Packets.
Each packet is like a small envelope: contains sender address, receiver address, and order number.
Packets may even take different routes but get reassembled at the end.
Rulebook that manages this method = TCP/IP Protocol.
IP Addresses
IPv4: Old system → has 4.3 billion unique addresses (seemed big, but we ran out).
Example: 192.168.1.1
IPv6: New system → uncountably huge number of addresses (enough for every atom in the galaxy).
Example: 2001:0db8:85a3:0000:0000:8a2e:0370:7334
Public vs Private IP
Public IP:Like your house's main address. Globally unique. Given by your ISP.
Private IP: Like room numbers in your house. Only make sense inside your local network.
Example: Your laptop has 192.168.1.100 at home, mine can have the same at my house, no conflict.
NAT (Network Address Translation): Your home router translates private IPs into your one public IP.
MAC Address
Every device (wifi card, phone, printer) has a unique “serial number” called a MAC Address burned into it.
Example: 3C:22:FB:A3:B4:C5
Think of it as the fingerprint of your device.
IP = house address (changeable), MAC = fingerprint (permanent).
Ports
Computers run many programs at once → how to know which program gets the message?
Solution: Port Numbers.
Like extensions in an office phone.
IP tells you which building, Port tells you which room.
Common Ports:
80 → Website (HTTP)
443 → Secure Website (HTTPS)
22 → Remote login (SSH)
27017 → MongoDB
DNS (Domain Name System)
Humans remember names, not numbers.
DNS = Internet's Phonebook. Converts names (google.com) to IPs.
Process when you search google.com:
Browser checks its local memory → maybe it already knows IP.
If not, it asks a DNS Resolver (usually ISP).
Resolver asks:
Root Server: Where is .com?
TLD Server (for .com): Where is google.com?
Authoritative Server (Google's own): What's the IP of www.google.com?
Answer (“142.250.x.x”) comes back to you.
Browser connects to that IP (over port 443 for HTTPS).
