Internet-Network

Fundamental Internet & Web Concepts Every Developer Must Know

What is the Internet?

The Internet is the largest network ever created by humans — a huge network of interconnected devices, servers, cables, and satellites.

Simple definition: The Internet is how computers and phones talk to each other.

When you search for something in a browser, your request travels through routers, ISPs, and servers, and the response returns in milliseconds.

The Internet is a global collection of networks that began in 1969 with four core hosts and has expanded massively since then. It belongs to no single entity.

How does the Internet work?

Main components:

• Devices: phone, laptop, tablet, smart TV
• Modem & Router: modem receives internet from ISP → router distributes
• ISP: gateway to the internet
• Servers: store and deliver information
• Cables & Satellites: physical paths of the data

What happens when you open a site?

Example: opening YouTube

1. You type youtube.com
2. Your device asks DNS for the IP
3. Modem sends request to ISP
4. ISP connects to nearest YouTube server
5. Server sends back the page
6. Browser displays it

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What is an ISP?

ISP = Internet Service Provider, the company that gives you internet access and routes your requests.

What does an ISP do?

• Connects you to the internet
• Assigns an IP
• Relays your requests
• Provides DNS
• Controls speed and quality
• Provides hosting and email services
• Ensures network security

Types of ISPs

• Home ISPs: ADSL, fiber, 4G/5G
• Web Hosting Providers: data centers, servers, cloud
• Backbone ISPs: international providers of global internet

Services ISPs Provide

• Internet connection
• IP address (static or dynamic)
• DNS
• Routing
• Server hosting
• Email services
• Network security
• Traffic filtering

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What is a Server?

A server is a computer that is always on and provides services to other devices (clients).

Server = provides service
Client = receives service

In web development, a server handles:

1. Receiving requests (HTTP/HTTPS)
2. Processing logic (backend, database)
3. Sending responses (HTML, CSS, JS, JSON)

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What Is Hosting?

Hosting is storage space on a server where your website’s files live so users can access the site.

How Hosting Works

1. You have a domain
2. Domain points to host’s IP
3. User sends request
4. Host sends files
5. Browser displays site

Types of Hosting

1. Shared Hosting

• Many sites on one server
• Cheap, limited resources

2. VPS (Virtual Private Server)

• Virtual server
• More control, better performance

3. Dedicated Server

• Entire server for one user
• Expensive, powerful

4. Cloud Hosting

• Distributed across servers
• Fast, scalable
• AWS, Google Cloud, Azure

5. WordPress Hosting

• Optimized for WordPress

6. Managed Hosting

• Fully managed by provider

Hosting Plans Include:

• Storage
• Bandwidth
• CPU & RAM
• Database support
• cPanel / DirectAdmin
• SSL
• Email
• Backups

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What Is a Domain?

A domain is a human-readable name like google.com that replaces numerical IP addresses.

How Domains Work

1. User enters domain
2. DNS converts domain → IP
3. Browser connects to server

Parts of a Domain

• Name: example
• TLD: .com, .net

Types of Domains

• TLDs (.com, .net…)
• Country domains (.ir, .uk…)
• Subdomains (blog.example.com)

Why Domains Matter?

• Easy access
• Branding
• Connect domain → host

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What is an IP Address?

An IP is a unique numerical address assigned to every device on the internet.

Why IP Matters

• Without IP, no connectivity
• Browser uses IP to reach server
• Ensures data reaches correct destination

Types of IP

IPv4

• Example: 192.168.1.1
• Limited capacity

IPv6

• Example: 2001:db8::8a2e
• Huge address range

Public vs Private IP

• Public: visible on internet
• Private: inside local network

Static vs Dynamic IP

• Static: fixed, good for servers
• Dynamic: changes, for home users

How IP Works

1. User enters domain
2. DNS finds IP
3. Browser connects to server
4. Site loads

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What is DNS?

DNS = Internet’s phone book
It converts domain names into server IP addresses.

Example:
google.com → 142.250.185.14

What DNS Does

• Converts domain → IP
• Caching for faster loading
• Provides redundancy and stability

How DNS Works

1. User enters domain
2. Browser asks DNS Resolver
3. If not cached → goes to root
4. Then TLD server (.com)
5. Then authoritative DNS
6. Returns IP → browser connects

Important DNS Records

• A: IPv4
• AAAA: IPv6
• CNAME: alias
• MX: mail server
• TXT: SPF, DKIM
• NS: DNS servers

Why DNS Is Important

• Website speed
• Security (DNSSEC)
• Domain ↔ host connection
• Email functionality
• Critical internet infrastructure

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What is HTTP?

HyperText Transfer Protocol
Defines how browsers and servers exchange data.

Features:

• Simple
• No encryption
• Fast
• Insecure → data readable by attackers

What is HTTPS?

HyperText Transfer Protocol Secure
Encrypted using SSL/TLS.

Features:

• Data encryption
• Server authentication
• Protection from MITM attacks
• Required for logins, payments

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What is an API?

API = Application Programming Interface
A communication bridge between applications.

Example

A weather website receives data from a weather API.

What APIs Do

1. Allow apps to communicate
2. Send/receive data (JSON/XML)
3. Prevent direct database access
4. Power modern applications

Importance for Developers

• All apps use APIs
• React/Vue/Next.js rely on APIs
• Used for:
  • Payments
  • Authentication
  • Markets
  • Social networks
  • Blockchain