Understanding Network Devices: How the Internet Reaches Your Device
We all use the internet today.
The most common way is via Wi-Fi or mobile data, with Wi-Fi being the most prominent.
Ever wondered how your device actually gets that Spotify song, YouTube video, or even shows you this particular blog?
It often feels like we are in a direct connection with Spotify or YouTube from our system - but that’s not the case.
There are multiple layers and multiple devices involved before a request from your device reaches a server and comes back with a response.
It’s also not that we weren’t connected to the world before the internet. We already had means like telephones and cable TV.
The internet is just another medium - one that expanded the horizon of what kind of data can be shared over an existing connection to the world.
Let’s break down the key devices that make this entire journey possible.
Modem - Translating Languages Between Worlds
In the earlier days of the internet, computers were connected using telephone lines:
Telephone Line → Modem → Ethernet Cable → Computer
We already had telephone connections with companies that were well connected across regions and countries.
The only issue was the language of communication.
Telephone lines understood analog signals
Computers spoke in digital signals
Telephones didn’t transmit our voice as-is.
The microphone converted sound into analog signals, sent them over the wire, and the receiver converted them back into sound.
Computers needed something similar - a way to convert their digital data into a form that telephone wires could understand.
This is where the modem came into existence.
A Modem (Modulator–Demodulator):
Converts digital signals → analog signals
Converts analog signals → digital signals
This translation allowed computers to communicate using existing telephone infrastructure.
Router – Making Sure Traffic Reaches the Right Device
As time passed, the number of devices increased and Wi-Fi came into existence.
Now a single household might have:
Phones
Laptops
TVs
Tablets
We can’t give each device its own internet connection like mobile phones do with SIM cards.
So the question became:
How do we connect multiple devices using a single internet connection?
If a single device is requesting data, it’s easy.
But with multiple devices, we need a way to identify who requested what.
Imagine:
You are watching a football match
Someone else in your home is watching cricket
Suddenly you start getting the cricket stream
That’s exactly what a router prevents.
A router:
Keeps track of devices
Ensures responses go back to the same device that requested them
This routing logic isn’t limited to homes.
Routers exist at all levels of the internet, connecting one logical network to another.
We’ll revisit this idea again later.
Router vs Modem – Do Routers Replace Modems?
It often feels like routers have replaced modems.
We commonly say:
“I have a fibre Wi-Fi router at home”
That statement is partially true.
If we recall what a modem actually does - signal translation - we’ll realize that routers never took over that responsibility.
A router manages and routes traffic (like a traffic policeman)
A modem translates signals so they can travel over physical media
What changed is integration.
Today:
Signal translation happens using light signals over fibre
This role is handled by something called an ONT
The modem functionality is hidden inside the same device
The idea remains the same - there is still a translator.
Analogy:
Earlier: a human translator
Now: Google Translate
Both do the same job; the implementation evolved.
So:
Modem and router both exist
They just live inside the same physical device in most homes today
Switch and Hub - Local Network Communication
So far, we’ve talked about connecting to the internet.
But sometimes we only need local communication, within a limited area like:
An office
A data center
A home network
For this, we use switches and hubs.
Routers can do this, but they are overkill.
A simple analogy:
Finding an item directly in a box
Versus opening a box, finding another box, and then finding the item
Switches are Layer 2 (L2) devices
Routers are Layer 3 (L3) devices
More layers = more processing.
Hub
A hub is like a railway station announcement.
Any message sent is broadcast to all ports
Every connected device receives it
Even if the message is meant for just one device
Switch
A switch is a smart hub.
It knows which devices are connected to which ports
Sends data only to the intended recipient
Analogy:
Hub → General announcement at a railway station
Switch → Airport announcements made for a specific gate
This makes switches faster and more efficient for local networks.
Firewall – Where Security Lives
Until now, we assumed:
We send data
Others receive it willingly
But what if:
Someone accesses data you never intended to share?
Someone sends commands to your device from anywhere in the world?
These are real problems.
Devices often respond to commands by default once they receive them.
That’s why we add security layers, such as:
Firewall
IDS / IPS
IAM
WAF
Antivirus
SIEM
A Firewall is one of these mechanisms.
Firewalls can operate at:
Layer 3
Layer 4
Layer 7
Or combinations of these
Analogy:
Some guards check badges
Some check bags
Some even listen to conversations
In general, when we say firewall, we usually mean L3 / L4 firewalls.
They:
Check source and destination IP
Check ports
Check protocol type
Track connections
This is why blindly disabling firewalls or allowing all traffic - just because a tutorial said so - is dangerous.
Your app might not be malicious, but opening everything can allow malicious actors into your system.
Security helps keep your application available and running.
But availability isn’t only about security - which brings us to the next component.
Load Balancer – Handling Scale and Availability
Think about:
A small local shop
A large supermarket
Now imagine two groups of 1000 people:
Group A goes to the supermarket
Group B goes to the local shop
Who gets served faster?
Most likely, Group A.
Why?
Supermarkets have:
Larger area
Well-defined sections
Multiple entry and exit points
Multiple billing counters
Local shops:
Small space
Single entry/exit
One billing counter
Local shops aren’t badly designed - they just aren’t meant to serve large traffic at the same time.
Now imagine:
A supermarket with multiple billing counters
But everyone lines up at a single counter
That defeats the purpose.
To fix this, we need someone directing people to different counters.
That person is the Load Balancer.
A load balancer:
Sits in front of backend servers
Distributes incoming traffic across multiple instances
Scaling backend servers alone isn’t enough.
Users don’t know:
Which instance exists
Which instance is free
Which instance is overloaded
So users always hit the load balancer, and it decides where the request should go.
Load balancers use different algorithms depending on needs and intelligence required.
How Everything Works Together – End-to-End Flow
Let’s trace how your request reached this blog.
Assume you are reading this from your office computer.
Flow
Open the browser
Enter the URL
Request goes via Ethernet connection to the switch
Switch forwards it to the router (where modem translates the signal)
Router sends the request to the ISP
Request passes through multiple routers
Reaches the ISP router of the hosting server
Router routes and translates the signal back to digital
Traffic goes to the switch
Switch sends it to the server
Server hosts a load balancer
Load balancer routes request to the appropriate backend server
The internal LAN and switches may be physical or virtual, and may not map 1:1 - but the logic remains the same.
Sum Up
All these devices:
Modem
Router
Switch
Hub
Firewall
Load Balancer
Are interesting in their own way and deserve deeper dives.
This write-up was meant to touch upon their responsibilities, how they differ, and how they work together to deliver something as simple as this blog to your screen.
