How the Internet Works

ip 🌐 IP

IP-local or the one assigned when you connect to the internet is a unique address for each device. When you connect to a different network, the IP changes.

types Types:

🌍 Public IP

Assigned by your ISP (Internet Service Provider). This exposes you to the outside world and makes you reachable.
🏠 Private IP

Used in local networks such as LAN, home, office, etc.
📍 Static IP

Typically assigned to servers and set manually.
🔄 Dynamic IP

Assigned temporarily by a DHCP (Dynamic Host Configuration Protocol) server.

mac 💻 MAC

MAC Address (Media Access Control Address) — a physical address.

It is tied to the hardware and cannot be changed (under normal conditions).

dns 📞 DNS

It’s like a contacts list. It translates website names to IP addresses.

People use names rather than memorizing IP addresses when visiting websites.

📌 Example: google.com IP → 142.250.190.14

protocols 📋 Protocols

A set of rules and standards that define how devices on the internet communicate, how data is sent, received, and interpreted.

The most famous ones: TCP/IP, OSI models

important-protocols Some important protocols:

🌐 HTTP / HTTPS (HyperText Transfer Protocol / Secure)

The fundamental protocol of the web. It provides the connection between Browser and Server (request, response).
🔒 TCP (Transmission Control Protocol)

A reliable, connection-oriented transport protocol.

Before sending data, it establishes a connection and then ensures it is complete, in order, and error-free.

Many protocols like HTTP, FTP, SMTP are built on top of TCP.
⚡ UDP (User Datagram Protocol)

Connectionless and fast, but less reliable transport protocol.

Data is sent without establishing a connection. There is no guarantee on delivery or order.

Used for video, audio streaming, and online games. (interview question!)
🔐 TLS / SSL (Transport Layer Security / Secure Sockets Layer)

This is the S in HTTPS. It’s added on top of TCP and encrypts communication and provides authentication.
📁 FTP / SFTP (File Transfer Protocol / Secure File Transfer Protocol)

Used for file transfers.
✉️ SMTP / IMAP / POP3

Email protocols.
🔄 WebSocket

Enables real-time, two-way (full-duplex) communication.

real-case-example 📌 Real-case example

When you connect to a website (www.example.com), this happens:

🔍 Your computer finds the IP address of the www.example.com domain via DNS.
📤 The browser creates a request packet according to the HTTP or HTTPS protocol rules.
📦 This request is segmented by the TCP protocol.
📍 Each TCP segment is placed into an IP packet with the IP address.
💻 Your computer determines the router’s MAC address (via ARP) to send the packet to it, and sends it via Ethernet.
🌐 The packet is delivered from router to router across the internet based on the IP address.
📍 Once it reaches the local network where the target server resides, the router delivers the packet to the server based on the MAC address.
✅ The server processes the packet according to the IP, TCP, and HTTP protocols and sends the response back the same way.