Siksha Sarovar

Siksha Sarovar (sikshasarovar.com) is a free educational web application that helps students in India learn programming and prepare for academic and competitive exams. The platform offers structured coding courses (C, C++, Python, Java, HTML, CSS, PHP, Power BI, AI, Machine Learning, Data Science), complete university curriculum notes for BCA/MCA students with previous year question papers, Class 10 and Class 12 CBSE/HBSE school notes, and dedicated preparation material for SSC, UPSC, Banking, Railway and other government exams. Browsing the site is completely free and requires no account. Users may optionally sign in with Google solely to save their learning progress, quiz scores and personal preferences across devices.

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Siksha Sarovar is a free e-learning platform for coding courses, BCA university notes and competitive exam preparation. Optional Google sign-in saves your learning progress across devices.

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Domain Names and DNS

Lesson 32 of 34 in the free Web Technologies notes on Siksha Sarovar, written by Rohit Jangra.

Domain Names and DNS

What is a Domain Name?

A domain name is the human-readable address for a website (e.g., www.google.com). It maps to an IP address that computers use to locate servers.

Domain Name Structure

https://www.blog.example.co.in
        │   │       │     │  │
        │   │       │     │  ccTLD (country-code)
        │   │       │     second-level TLD
        │   │       second-level domain
        │   subdomain
        protocol

Types of Domains

Top-Level Domains (TLDs)

TypeExamples
Generic (gTLD).com, .org, .net, .edu, .gov
Country Code (ccTLD).in, .uk, .us, .jp
New gTLDs.app, .shop, .blog, .tech
Sponsored.edu, .gov, .mil

Domain Levels

LevelExample
Root. (implicit)
TLD.com
Second-levelgoogle.com
Subdomainmail.google.com

Domain Name System (DNS)

DNS (Domain Name System) is the "phone book" of the Internet — it translates domain names to IP addresses.

DNS Resolution Process

Browser asks: What is the IP of www.example.com?
    ↓
Check browser cache → Check OS cache → Check /etc/hosts
    ↓ (if not found)
DNS Resolver (ISP's server)
    ↓
Root Name Server (.) → .com TLD Server → example.com Authoritative Server
    ↓
Returns: 93.184.216.34
    ↓
Browser connects to IP address

DNS Record Types

RecordPurposeExample
ADomain → IPv4example.com → 93.184.216.34
AAAADomain → IPv6example.com → 2606:2800::1
CNAMEAlias to another domainwww → example.com
MXMail exchange servermail.example.com
NSName server recordsns1.hostprovider.com
TXTText records (SPF, verification)"v=spf1 include:..."
PTRReverse DNS lookupIP → domain
SOAStart of authorityZone info

Registering a Domain

  1. Choose a registrar (GoDaddy, Namecheap, Google Domains)
  2. Search for availability
  3. Register for 1–10 years
  4. Set up DNS records at your hosting provider

TTL (Time to Live)

DNS records have a TTL value (in seconds) that determines how long they're cached:

  • Low TTL (300s) – faster propagation but more DNS queries
  • High TTL (86400s = 24h) – fewer queries but slow changes

DNS Propagation

When you change DNS records, propagation across the Internet takes 24–48 hours due to caching at various DNS servers.

Key Takeaway: DNS translates human-readable domain names to IP addresses through a hierarchical resolution process. Understanding DNS records (A, CNAME, MX, TXT) is essential for deploying websites and configuring email services.