Turning Learners into Developers
- Introduction to the Internet
The Internet is a global network of interconnected computers that communicate using standard protocols. Every device connected to the internet needs a unique address to identify itself.
- What Is a Domain Name?
A Domain Name is a human-readable address used to access a website on the internet. Example : www.codekilla.com
- Why Domain Names Are Needed
- Easy to remember
- Represents brand identity
- Replaces numeric IP addresses
- Essential for businesses and professionals
- Structure of a Domain Name
Part | Example | Full Form |
|---|---|---|
Subdomain | www | World Wide Web (commonly used, but technically optional) |
SLD | codekilla | Second-Level Domain |
TLD | .com | Top-Level Domain |
“www” stands for World Wide Web, but it's not required for a website to function. Many modern sites work without it ( | ||
- Types of Domain Extensions
gTLD – Generic Top-Level Domain
- .com – Commercial
- .org – Organization
- .net – Network
- .tech – Technology
- .ai – Artificial Intelligence
ccTLD – Country Code Top-Level Domain
- .in – India
- .us – United States
- uk – United Kingdom
nTLD – New Top-Level Domain
- .dev – Developer
- .io – Input / Output
- .design – Creative field
- What Is DNS?
DNS – Domain Name System
DNS converts domain names into IP addresses so browsers can locate web servers.
codekilla.com → 192.168.1.1
DNS works like the Internet’s phonebook.
- How DNS Works (Step-by-Step)
- User types a domain name. Example: www.codekilla.com
- Browser queries DNS server. The browser asks the DNS resolver: “What is the IP address for this domain?”
- DNS returns IP address. Example: 192.0.2.1
- Browser connects to server. Using the IP address, the browser establishes a connection with the web server.
- Website loads. The server responds with the website content, and the page is displayed.
- What Is an IP Address?
IP Address – Internet Protocol Address
An IP address uniquely identifies a device on a network.
Methods to Find a Domain’s IP Address
- Open Command Prompt - Press Windows Key + R - Type cmd and press Enter
- Type nslookup codekilla.com
- DNS server queried
- IP address returned
- Result displayed in Command Prompt
Note: If the domain uses a CDN (like Cloudflare), the IP shown may belong to the CDN rather than the origin server.
- Types of IP Addresses
IPv4 : Internet Protocol Version 4
- IPv4 addresses are made up of 32 bits, divided into 4 octets (8 bits each).
- Each octet is written in decimal format, ranging from 0 to 255.
- The format is called dotted-decimal notation: Example → 192.168.1.1
Octet | Binary (8 bits) | Decimal |
|---|---|---|
1st | 11000000 | 192 |
2nd | 10101000 | 168 |
3rd | 00000001 | 1 |
4th | 00000001 | 1 |
- Each octet is converted from binary to decimal.
- Together, they form the full IP address: 192.168.1.1
Optional: Convert to Single Decimal Number
You can also convert the full IP into a single 32-bit decimal number using this formula:
Decimal IP=(192×2563)+(168×2562)+(1×2561)+(1×2560) =(192×16777216)+(168×65536)+(1×256)+1=3232235777
So 192.168.1.1 = 3232235777 in pure decimal format
- To convert to a single decimal number, we treat it as base 256.
- 256³ means “256 raised to the power of 3,” not “2563.”
- Each octet’s position determines which power of 256 it’s multiplied by:
- 1st octet → 2563 | 2nd octet → 2562 | 3rd octet → 2561 | 4th octet → 2560
- Dotted-decimal is human-friendly.
- Pure decimal is used in some network tools, databases, and low-level configurations.
- Total Addresses : 2 32 = 4.3 billion
IPv6 : Internet Protocol Version 6
- IPv6 is the 128-bit successor to IPv4 (which is 32-bit).
- It allows for vastly more unique addresses — about 3.4 × 1038 possible combinations.
- IPv6 addresses are written in hexadecimal format, not decimal like IPv4.
- It consists of 8 groups of 4 hexadecimal digits.
- Each group represents 16 bits.
- Total: 8 × 16 = 128 bits.
- Example : 2001:0db8:85a3:0000:0000:8a2e:0370:7334
Segment | Hex Value | Binary (16 bits) |
|---|---|---|
1 | 2001 | 0010000000000001 |
2 | 0db8 | 0000110110111000 |
3 | 85a3 | 1000010110100011 |
4 | 0000 | 0000000000000000 |
5 | 0000 | 0000000000000000 |
6 | 8a2e | 1000101000101110 |
7 | 0370 | 0000001101110000 |
8 | 7334 | 0111001100110100 |
- Omit leading zeros: 0370 → 370
- Use double colons (::) to compress consecutive zeros: 2001:0db8:0000:0000:0000:0000:1428:57ab → 2001:db8::1428:57ab
- Total Addresses : 2 128 ≈ 340 undecillion
- DNS Records
Record | Full Form | Purpose | Example |
|---|---|---|---|
A | Address Record | Maps to IPv4 | example.com → 192.168.1.1 |
AAAA | Quad-A Record | Maps to IPv6 | example.com → 2001:db8::1 |
CNAME | Canonical Name | Domain alias | www.example.com → example.com |
MX | Mail Exchange | Email routing | mail.google.com |
TXT | Text Record | Verification | SPF / DKIM |
NS | Name Server | DNS authority | ns1.host.com |
SPF : Sender Policy Framework | Authorizes mail servers. DKIM : DomainKeys Identified Mail | Adds digital signature to emails. DMARC : Domain-based Message Authentication, Reporting & Conformance | Controls failed email handling. | |||
- SSL (Secure Sockets Layer)
SSL (Secure Sockets Layer) is a security technology used to encrypt data transmitted between a user’s browser and a web server. This encryption ensures that sensitive information cannot be read or stolen by attackers.
What SSL Protects
- Login credentials (username & password)
- Credit/debit card details
- Personal and confidential data
- Form submissions
How SSL Works (Simple Flow)
- Browser requests a secure connection
- Server sends an SSL certificate
- Browser verifies the certificate
- Encrypted communication starts
With SSL :
https://www.codekilla.com
All data exchanged is encrypted.
Without SSL :
http://www.example.com
Data is sent in plain text, which is unsafe.
- HTTPS (HyperText Transfer Protocol Secure)
HTTPS (HyperText Transfer Protocol Secure) is the secure version of HTTP that uses SSL (or TLS [Transport Layer Security]) to encrypt communication between browser and server.
HTTPS = HTTP + SSL/TLS
How to Identify HTTPS
- Website URL starts with https://
- Lock (🔒) symbol in the browser address bar
Example of HTTPS Usage
- Online banking websites
- E-commerce platforms
- Login pages
- Payment gateways
- Difference Between HTTP and HTTPS
Feature | HTTP | HTTPS |
|---|---|---|
Full Form | HyperText Transfer Protocol | HyperText Transfer Protocol Secure |
Security | Not secure | Secure |
Encryption | No encryption | Data encrypted using SSL/TLS |
Data Safety | Low | High |
SEO Ranking | Lower | Higher |
URL Example | http://example.com | https://example.com |
Login Example | Password sent as plain text | Password sent as encrypted data |
Browser Display | “Not Secure” warning | 🔒 Lock symbol shown |
- Internet / Networking Commands in CMD (Windows)
| Command | Full Form / Meaning | Purpose | Example |
|---|---|---|---|
ipconfig | Internet Protocol Configuration | Shows IP address, gateway, DNS | ipconfig |
ipconfig /all | - | Displays detailed network info | ipconfig /all |
ipconfig /release | - | Releases current IP address | ipconfig /release |
ipconfig /renew | - | Renews IP address from DHCP(Dynamic Host Configuration Protocol) | ipconfig /renew |
ping | Packet Internet Groper | Checks connectivity to a host | ping google.com |
tracert | Trace Route | Shows path packets take to destination | tracert google.com |
nslookup | Name Server Lookup | Checks DNS records | nslookup codekilla.com |
netstat | Network Statistics | Shows active connections | netstat -an |
arp | Address Resolution Protocol | Shows IP–MAC mapping | arp -a |
pathping | Path + Ping | Network path & packet loss | pathping google.com |
route | Routing Table | Displays or modifies routing table | route print |
hostname | Host Name | Shows computer name | hostname |
getmac | Get MAC Address | Displays MAC address | getmac |
whois | Domain Info Lookup | Shows domain registration info | whois example.com |
telnet | Teletype Network | Tests port connectivity | telnet google.com 80 |
ftp | File Transfer Protocol | Transfers files over network | ftp ftp.example.com |
curl | Client URL | Fetches data from URLs | curl https://example.com |
netsh | Network Shell | Network configuration | netsh wlan show profiles |
net use | Network Use | Connects shared resources | net use Z: \\server\share |
net view | Network View | Lists computers in network | net view |
nbtstat | NetBIOS Statistics | NetBIOS info & cache | nbtstat -n |
CMD networking commands are used to configure, troubleshoot, and monitor internet and network connections in Windows systems. | |||
- What DHCP Does
- Automatic IP Assignment: It dynamically assigns IP addresses to devices on a network, so you don’t have to configure them manually.
- Other Settings: Provides subnet mask, default gateway, and DNS server information.
Client–Server Model:
- DHCP Server (often your router) manages a pool of IP addresses.
- DHCP Client (your computer, phone, etc.) requests an IP when connecting.
- The server leases an IP address to the client for a set period.
Why It’s Useful
- Saves time by eliminating manual configuration.
- Prevents IP conflicts by ensuring each device gets a unique address.
- Makes networks more scalable and easier to manage.
- DHCP Process (DORA)
- Discover - The client (your computer or phone) sends a broadcast message: “Is there a DHCP server out there? I need an IP address!”
- Offer - A DHCP server responds with an offer: “Here’s an IP address you can use, along with subnet mask, gateway, and DNS info.”
- Request - The client replies with a request: “I’d like to use the IP address you offered.”
- Acknowledge - The DHCP server sends an acknowledgment: “Confirmed! That IP address is now leased to you for a certain time.”
Example in Action
- You connect your laptop to Wi-Fi.
- Laptop sends Discover.
- Router (acting as DHCP server) sends Offer: 192.168.1.25.
- Laptop sends Request for 192.168.1.25.
- Router sends Acknowledge confirming the lease.
- Now your laptop can communicate on the network with that IP.
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