🌐 Today's Article: How Data Actually Travels Through a Network
Today I learned intermediate networking concepts including DNS, IP addresses, TCP, ports, routing, and ARP, along with their role in AWS VPCs, subnets, Security Groups, and EC2. This strengthened my understanding of how data travels across networks and built a foundation for AWS and DevOps.
When you open a website such as https://example.com, your computer doesn't simply "send a request to the website." Several networking layers and devices work together.
1. DNS — Finding the server
You type:
https://example.com
Your computer first needs the server's IP address.
DNS converts:
example.com
↓
93.184.216.xxx
Think of DNS as the phonebook of the Internet.
2. TCP — Establishing communication
For HTTPS traffic, your application normally uses TCP.
TCP establishes a connection using the famous 3-way handshake:
Client Server
1. DNS — Finding the server
You type:
https://example.com
Your computer first needs the server's IP address.
DNS converts:
example.com
↓
93.184.216.xxx
Think of DNS as the phonebook of the Internet.
2. TCP — Establishing communication
For HTTPS traffic, your application normally uses TCP.
TCP establishes a connection using the famous 3-way handshake:
Client Server
SYN -------------------->
<---------------- SYN + ACK
ACK -------------------->
Now both sides are ready to communicate.
TCP provides things such as:
Reliable delivery
Ordering of packets
Retransmission of lost data
Flow control
3. IP — Finding the destination
The IP layer is responsible for moving packets between networks.
For example:
Your Laptop
↓
Router
↓
ISP
↓
Internet
↓
AWS Network
↓
Web Server
Routers examine the destination IP address and decide where the packet should go next.
4. MAC Address — Communication inside a local network
IP addresses help identify destinations across networks.
But inside your local network, devices communicate using MAC addresses.
For example:
IP address:
192.168.1.20
<---------------- SYN + ACK
ACK -------------------->
Now both sides are ready to communicate.
TCP provides things such as:
Reliable delivery
Ordering of packets
Retransmission of lost data
Flow control
3. IP — Finding the destination
The IP layer is responsible for moving packets between networks.
For example:
Your Laptop
↓
Router
↓
ISP
↓
Internet
↓
AWS Network
↓
Web Server
Routers examine the destination IP address and decide where the packet should go next.
4. MAC Address — Communication inside a local network
IP addresses help identify destinations across networks.
But inside your local network, devices communicate using MAC addresses.
For example:
IP address:
192.168.1.20
MAC address:
AA:BB:CC:11:22:33
ARP helps discover the MAC address associated with an IPv4 address on the local network.
🔥 The important concept: Ports
An IP address identifies a machine/interface.
A port identifies a service/application on that machine.
For example:
192.168.1.10:22
↑
SSH
Common ports:
Port
Protocol
Common use
22
SSH
Remote Linux access
53
DNS
Domain resolution
80
HTTP
Web
443
HTTPS
Secure web
3306
MySQL
Database
5432
PostgreSQL
Database
So:
IP address + Port
↓
192.168.1.10:22
means connect to port 22 on that machine.
☁️ Why this matters in AWS
Suppose you create an AWS EC2 server.
Your architecture might look like:
Internet
↓
Public IP
↓
Internet Gateway
↓
VPC
↓
Subnet
↓
Security Group
↓
EC2
↓
Application
If your Spring Boot application runs on:
Port 8080
you might have:
Client
↓
EC2 public IP : 8080
↓
Security Group
↓
Spring Boot application
The Security Group determines whether traffic to that port is allowed.
This is why networking fundamentals are extremely important before learning AWS deeply.
🧠 Today's key takeaway
Remember this chain:
DNS → IP → Routing → TCP → Port → Application
And for AWS:
Internet → VPC → Subnet → Security Group → EC2 → Application
AA:BB:CC:11:22:33
ARP helps discover the MAC address associated with an IPv4 address on the local network.
🔥 The important concept: Ports
An IP address identifies a machine/interface.
A port identifies a service/application on that machine.
For example:
192.168.1.10:22
↑
SSH
Common ports:
Port
Protocol
Common use
22
SSH
Remote Linux access
53
DNS
Domain resolution
80
HTTP
Web
443
HTTPS
Secure web
3306
MySQL
Database
5432
PostgreSQL
Database
So:
IP address + Port
↓
192.168.1.10:22
means connect to port 22 on that machine.
☁️ Why this matters in AWS
Suppose you create an AWS EC2 server.
Your architecture might look like:
Internet
↓
Public IP
↓
Internet Gateway
↓
VPC
↓
Subnet
↓
Security Group
↓
EC2
↓
Application
If your Spring Boot application runs on:
Port 8080
you might have:
Client
↓
EC2 public IP : 8080
↓
Security Group
↓
Spring Boot application
The Security Group determines whether traffic to that port is allowed.
This is why networking fundamentals are extremely important before learning AWS deeply.
🧠 Today's key takeaway
Remember this chain:
DNS → IP → Routing → TCP → Port → Application
And for AWS:
Internet → VPC → Subnet → Security Group → EC2 → Application
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