WorkFlows.
1 . Browser → DNS → Server (high-level flow)
Now The Final Part That How Everything Comes In Place.
Let’s Decode How Everything Comes In Place.
1. Browser
The user enters a website URL in the browser.
The browser sends a request to load the page.
2. DNS
DNS converts the domain name into an IP address.
This tells the browser where the server is located.
3. Web Server
The browser sends the request to the web server.
The server processes the request.
4. Database Server
If data is needed, the web server asks the database.
The database returns the required data.
5. Response back to browser
The web server sends the final response back.
The browser renders and shows the web page.
2. Domain name to IP mapping using A / AAAA records.
Understanding The Image.
Big picture (before details)
DNS records are just data lookups.
This diagram shows how AAAA records travel through DNS servers to a system.
1. Authoritative Name Server
This server stores DNS records for a domain.
It answers questions about that domain’s records.
2. AAAA Record request
A system asks DNS for an AAAA record.
This means it wants the IPv6 address of a domain.
3. Recursive DNS Server
The recursive server asks on behalf of the user.
It collects the answer and passes it forward.
4. Response with IPv6 address
The authoritative server replies with an IPv6 value.
This is normal DNS behavior for AAAA records.
5. System receives the response
The system receives the IPv6 address.
It then decides what to do next (connect or ignore).
What beginners should actually learn from this
AAAA records are just IPv6 mappings
DNS servers pass data, not commands
DNS itself does not execute code
Systems must still validate and handle data safely.
3. CNAME pointing one domain name to another ( Flow)
We Will Understand The Flow Displayed By The Diagram.
Generic Way.
Think of asking for a person by nickname.
You are redirected until you reach their real name and address.
1. Client (Browser)
The user types a domain name in the browser.
The browser does not know the IP address yet.
2. DNS Recursive Resolver
The request goes to the recursive DNS resolver.
This resolver finds the answer on behalf of the user.
3. DNS Root Name Server
The resolver asks the root server.
The root server points to the correct top-level domain server.
4. DNS Top-Level Domain (TLD) Server
The resolver asks the TLD server (like .com).
The TLD server points to the authoritative name server.
5. Authoritative Name Server (CNAME found)
The authoritative server checks the records.
It replies with a CNAME record, not an IP address.
6. Follow the CNAME target
The resolver now looks up the target domain name.
This starts another DNS lookup.
7. Final authoritative server (A / AAAA record)
The resolver reaches the final authoritative server.
It receives the A or AAAA record with the IP address.
8. IP returned to the client
The resolver sends the IP address back to the browser.
The browser now connects to the web server.
Key beginner clarity (important)
CNAME does not give an IP ❌
CNAME points to another domain name ✅
DNS keeps following names until it finds A or AAAA.
4. Email routing using MX records.
This Image Clearly Shows OR Explains How The MX Helps Email’s
STEP 1: DNS query for MX records
When an email is sent to user@example.com,
the sender’s mail server asks DNS for MX records of example.com.
DNS returns:
Mail server hostnames
Their priority numbers
STEP 2: Priority organization
The mail server sorts MX records by priority.
Lower number = higher priority.
Example:
mail1.example.com → priority 10
mail2.example.com → priority 20
mail3.example.com → priority 30
The server tries priority 10 first.
STEP 3: IP resolution & connection
MX records point to hostnames, not IP addresses.
So the mail server looks up A / AAAA records for that hostname.
After getting the IP,
it opens an SMTP connection (port 25).
Primary server availability check
If the primary mail server is available → continue.
If not → try the next priority server (RFC 5321 rule).
This ensures reliable email delivery.
Email delivered
Once a mail server accepts the message,
the email is delivered to the recipient’s mailbox.
Important warning (bottom of the image)
If no MX records exist:
Some systems fall back to the domain’s A record.
This is:
Unreliable
Prone to failures
Not recommended
Key beginner clarifications (very important)
MX records do NOT point to IPs ❌
MX records point to mail server names ✅
A / AAAA records give the actual IP
Priority decides which server is tried first
5. Simple DNS hierarchy showing NS records
Lets Decode This With Diagram.
This Image Exactly Show How DNS Works THE FLOW.
Generic example
Think of addresses managed in levels.
Country → State → City → House.
DNS works the same way.
1. Root Domain (.)
What problem it solves:
Where does DNS start?
Role:
Root DNS servers know which name servers manage each TLD.
They return NS records for .com, .org, .edu, etc.
2. Top-Level Domains (TLDs)
Examples: .com, .net , .org , .edu
What problem they solve:
Who manages domains under this extension?
Role:
TLD servers store NS records for domains like google.com or wikipedia.org.
They point to the domain’s authoritative name servers.
3. Authoritative DNS Servers
Examples:
google.com, wikipedia.org, harvard.edu
What problem they solve:
Where are the final answers?
Role:
Authoritative servers store the actual DNS records:
A, AAAA, CNAME, MX, TXT, etc.
How NS records connect everything (key idea)
Root NS → tells who manages .com / .org
TLD NS → tells who manages google.com
Authoritative NS → gives final answers
NS records form the chain of responsibility.
6 . One complete DNS setup for a small website.
Complete Setup !
Big picture (first)
This diagram shows how DNS works at scale.
It is used by companies handling millions of DNS queries.
Step-by-step explanation
1. Users (left side)
Users try to open websites or apps.
Each action creates a DNS query.
2. DNS Load Balancer
All DNS queries first hit the DNS Load Balancer.
Its job is to distribute traffic evenly.
This prevents one DNS server from getting overloaded.
3. DNS Dispatcher layer
The dispatcher receives queries from the load balancer.
It routes requests to available DNS resolvers.
Think of it as a traffic controller.
4. Policy Enforcement & DNS Resolver (BIND)
This is the core DNS brain.
It:
Resolves DNS queries
Enforces rules (block, allow, redirect)
Uses software like BIND
This is where the actual DNS answer is decided.
5. Cloud DNS & DNS Database
If the resolver needs records:
It queries Cloud DNS
Records are fetched from the DNS Database
This database stores:
A, AAAA, CNAME, MX, TXT, etc.
6. Configuration Management
Admins manage DNS rules and records here.
Any change flows down to dispatchers and resolvers.
This ensures consistent DNS behavior everywhere.
7. Monitoring & Scaling
DNS traffic is continuously monitored.
If load increases, the system scales automatically.
This keeps DNS fast and reliable.
8. Analytics & Threat Insight (top layer)
DNS data is analyzed using tools like:
Apache Spark
Kafka
Hadoop
This helps detect:
Malware domains
Suspicious traffic
DNS abuse
9. Admin control
Admins observe dashboards and alerts.
They tune policies, block threats, and optimize performance.
How this differs from a “small website DNS”
Small website DNS:
Registrar
NS → A → MX → TXT
This diagram:
Load balancing
Security enforcement
Analytics
High availability
Massive scale