Lesson 11 — Intermediate

Internet & Web (HTTP, DNS, URL)

Internet duniya ka sabse bada network, aur Web uspe chalne wala content. Is lesson mein hum dekhenge URL kaise kaam karta hai, DNS kya hai, aur HTTP/HTTPS ka role — jab bhi tum koi site kholte ho ye sab hota hai.

⏱ 14 min• Intermediate• Networks Basics

Internet aur Web mein farak

WHAT

Internet = duniya bhar ke networks ka interconnected network (infrastructure). Web (WWW) = us internet pe chalne wala information system (pages, sites). Internet Web ke bina chal sakta hai, Web internet ke bina nahi.

WHEN

Jab bhi browser mein kuch kholo — tum Web use kar rahe ho, jo internet (infrastructure) par chalta hai. Email, FTP bhi internet use karte hain par Web nahi.

WHERE

Internet = cables, routers, ISPs. Web = websites, pages, links jo browser mein dikhte hain.

Simple: Internet = sadkein, Web = un sadkon pe chalne wali dukaanein (websites). Ye farak exam mein poochha jaata hai.

URL aur HTTP/HTTPS

URL structure:
https://www.dswallah.com/learn/
│        │              │
protocol host           path

Protocol : HTTP (port 80) / HTTPS (port 443, SSL/TLS encrypted)
HTTP     : request-response protocol (client ↔ server)
HTTPS    : HTTP + encryption — safe (padlock dikhta hai)

GET / HTTP/1.1  ← browser request
Host: example.com

HTTP/1.1 (persistent) / HTTP/2 (multiplexing) / HTTP/3 (QUIC)

Yaad rakho: HTTP = port 80, HTTPS = port 443. HTTPS mein SSL/TLS certificate hota hai jo data encrypt karta hai — isi liye safe hai. HTTP mein data plain jaata hai (risk).

DNS — internet ka phonebook

Tum "dswallah.com" type karte ho, computer ko chahiye IP address (number). DNS (Domain Name System) in dono ko map karta hai — jaise phonebook naam se number dhoondhta hai:

DNS resolution steps:
1. Browser cache check → mil gaya? done
2. OS cache / router cache
3. Recursive resolver (ISP)
4. Root server → TLD server (.com) → Authoritative server
5. IP mila (example: 93.184.x.x) → browser connect karta hai

dswallah.com → 142.250.x.x (IP) → server se page mila

Domain levels : example.com
               │     │
               host  TLD (.com, .in, .org)

DNS hamesha hierarchical aur distributed hai — ek server pe nahi, poore system pe chalta hai. Isliye itna fast milta hai.

Browser kaise page load karta hai

URL parse karta hai (protocol, host, path).
DNS lookup se IP address nikaalta hai.
TCP connection banata hai (port 80/443) + HTTPS mein TLS handshake.
HTTP request bhejta hai (GET /).
Server response deta hai (HTML, status 200).
Render — HTML parse, CSS apply, JS run → page dikhta hai.

Status codes (common):
200 OK         : success
301 Moved      : permanent redirect
302 Found      : temporary redirect
403 Forbidden  : access denied
404 Not Found  : page nahi mili
500 Server Err : server pe problem

Exercise

Question: HTTPS ka default port number kya hai? Sirf number daalo.

Question: DNS ka full form kya hai? (do words, space se).

Question: 404 status code ka matlab kya hai? (page not found / ok / forbidden)

Common mistakes

Internet aur Web ko same samajhna: Internet = infrastructure (networks), Web = uspe chalne wale pages. Internet Web ke bina bhi chalta hai (email).
DNS aur IP ka farak ulta bolna: DNS naam→IP map karta hai. IP address number hai, domain naam hai. DNS phonebook hai.
HTTP aur HTTPS ka farak na pata hona: HTTPS = HTTP + SSL/TLS encryption. Port 443 vs HTTP ka 80.

Desi example: Roz ka browser workflow

Jab tum Google kholte ho — ye sab milliseconds mein hota hai (DNS, connection, request, render):

Type google.com
→ DNS: naam → IP
→ TCP + TLS handshake
→ GET request
→ 200 OK (HTML mila)
→ render → page dikha

Exam mapping (TCS / CUET)

TCS NQT: DNS ka full form + HTTP/HTTPS port.
CUET: Internet vs Web difference.
Trap: "HTTPS uses port 80" — galat, wo 443 hai.

Lesson complete?

Internet samajh aa gaya. Agla lesson — Computer Security — mein dekhenge threats aur protection.