HTML Mastery: 6-Day Learning Journey

Internet and IP Address

Internet: The internet is a worldwide system of connected networks that lets devices communicate and share information using IP addresses and standard protocols.

What is an IP Address?

• IP (Internet Protocol) address is a unique number given to every device connected to the internet.
• It acts like a digital address so data knows where to be delivered.

How IP Address is Allotted?

• When you connect to the internet, your ISP (Internet Service Provider) assigns an IP address to your device.
• When you disconnect, the same IP address can be released and assigned to someone else.
• - This is called a Dynamic IP.

Static vs Dynamic IP:

• Dynamic IP → Changes every time you connect. Most common, provided automatically by ISP.
• Static IP → Fixed address that doesn’t change, usually used by servers, websites, and companies.

Why Do We Need DNS?

• Computers communicate using IP addresses (like 142.250.182.14).
• But remembering these numbers is hard for humans.
• DNS (Domain Name System) works like a phonebook — it maps easy-to-remember domain names (like google.com) to IP addresses.

Flow of Accessing a Website:

• You type a website name in your browser (e.g., youtube.com).
• Browser asks the DNS server for the IP address of that domain.
• DNS server responds with the correct IP address.
• Your device then uses that IP to connect to the web server and load the website.

MAC Address and Port number

• A MAC address is like the serial number of your device’s network card.
• It is unique for every device (like your fingerprint).
• It never changes because it is built into the hardware.

Why it is Needed?

• To identify devices in a local network (like Wi-Fi or LAN).
• To make sure data goes to the right device inside the network.
• Used for network security (like blocking/allowing devices).

MAC address = Your device’s permanent home address inside the local network.
IP address = The temporary address given when you connect to the internet.

Ways to Send or Receive Data

1. Unicast
   • Data is sent from one device to exactly one device.
   • Example: Your laptop sending a file directly to your friend’s laptop.
2. Broadcast
   • Data is sent from one device to all devices in the local network.
   • Example: When a device first joins a network, it sends a broadcast asking “Who is the DHCP server?”
3. Multicast
   • Data is sent from one device to a selected group of devices.
   • Example: Online video streaming where the same video is delivered to many viewers at once without sending separate copies.

HTTP vs HTTPS

• HTTP (HyperText Transfer Protocol):
  • Transfers data between browser & website in plain text.
  • Data can be intercepted by others.
• HTTPS (HyperText Transfer Protocol Secure):
  • Secure version of HTTP using SSL/TLS encryption.
  • Keeps sensitive data (passwords, payments) safe from hackers.

Example:

1. Login with HTTP → Username & password can be stolen.
2. Login with HTTPS → Data is encrypted & secure.

IPv4 vs IPv6

• IPv4:
  • 32-bit, written as dotted decimal (e.g., 192.168.1.1).
  • ~4.3 billion addresses.
• IPv6:
  • 128-bit, written in hexadecimal (e.g., 2001:db8::7334).
  • Huge address space (340 undecillion).
  • Faster routing, built-in security (IPSec).

Why IPv6?

• IPv4 addresses were running out due to internet growth & IoT.
• IPv6 solves shortage and adds better features.

Switch vs Router

Switch

• Connects multiple devices inside a LAN.
• Uses MAC addresses to forward data.
• Works at Data Link Layer (Layer 2).

Router

• Connects different networks (e.g., home to internet).
• Uses IP addresses to send data.
• Works at Network Layer (Layer 3).

In short:

• Switch: Connects devices in same network (MAC).
• Router: Connects networks & internet (IP).

Public vs Private IP

Public IP

• Given by ISP, unique worldwide.
• Used for communication on internet.

Private IP

• Used inside a local network.
• Not unique globally, cannot be accessed directly from internet.

Why Both?

• Private IP → Local communication inside LAN.
• Public IP → Connects to outside internet.
• NAT translates between them.

Example:

• Laptop → Private IP 192.168.1.5.
• Router → Public IP 122.178.44.11.

Web Development & Client–Server Model

Client–Server Model

• Client: Browser/device sending request.
• Server: Stores data/websites & responds.
• Example: Google.com → Browser requests → Server responds.

Frontend (Client-side)

• HTML: Structures content.
• CSS: Styles content.
• JavaScript: Adds interactivity.

Backend (Server-side)

• Handles data, logic, databases.
• Examples: Node.js, Python, Java, PHP.

Flow:

1. User → Browser (Client).
2. Request sent to Server.
3. Server processes & responds with HTML, CSS, JS.
4. Browser displays page.