Now we know what is term internet & how it was used in 70’s it became global in late 1991 as The term WWW came to existence (World Wide Web) A system that runs on top of internet that lets you access the information through an interface called as (websites , webpages) that contains the information that an user needs.

What is a Modem?

A modem is a device that acts as a medium between the user and the ISP (Internet Service Provider). It converts the signals sent by the ISP into digital data that computers and other devices can understand.

Modem Workflow

• ISP sends signals (via fiber, cable, or phone line).

• Modem receives the signal.

• Modem converts the signal into digital data.

• Data is sent to the router.

What is a Router?

A router is a device that connects multiple devices to the internet. It receives digital data from the modem and sends it to the correct device such as laptops, mobiles, or TVs.

Router Workflow

• Router receives internet data in the form of packets.

• Each packet contains a destination IP address.

• Router reads the destination IP address.

• It selects the best available path.

• The packet is forwarded to the destination device.

What is a Packet?

A packet is a small unit of internet data made up of bits.
Internet data is sent packet by packet instead of all at once to prevent network overload and enable high-speed communication.

The term router is an device that converts the signals of modem into the signals that can be received to your peripheral devices i e (mobile, laptop , tab) & much more router is the mediator between the signals that are understood by the router itself so that it can direct the flow of network to the mobile & laptops.

How The Router Directs The Traffic Of Signals.

In basic terms consider the router as an google map which will show you the shortest path possible to your destination so that you can reach faster.

Now the router does also the same process.

1. It receives the signals from the (modem which receives signals from the ISP jio , airtel)

2. Now those signals cannot be directly sent to the mobile or laptop.

3. Here comes the router the mediator(saviour)

4. Router Transforms the data packets information to bits

5. The bits now locates the Destination IP address of the target

6. It now searches for the shortest path possible so that the data can be received faster.

7. When the path is found it will send the data to local device & keeps on sending the net ie data packets to the receiver.

2.Switch vs Hub: how local networks actually work?

In a local area network, devices like computers and printers need a device to connect and communicate with each other. Hub and switch are two such devices used for this purpose. Even though both are used in LAN, the way they handle data is very different which affects speed and performance of network.

Here Are the Points To Understand.

• A hub sends the data to all connected devices even if only one device needs it, this creates lot of unnecessary traffic.

• Because hub sends data everywhere, collisions can happen when two devices sends data at same time.

• A switch is more intelligent and sends data only to the specific device using MAC address.

• Switch reduces network traffic and improves overall speed and efficiency.

• Today hubs are mostly outdated and switches are commonly used in home and office networks.

3. What is a Firewall and why security lives here?

A firewall is a security device or software that helps protect a network from unwanted access. It works like a gatekeeper between your internal network and the outside world like internet. Whenever data tries to enter or leave the network, firewall checks it based on certain rules and then decides whether to allow it or block it. This is why most of the network security actually lives at firewall level.

• Firewall monitors incoming and outgoing network traffic all the time.

• It blocks unauthorised access while allowing trusted data to pass through.

• Firewalls can be hardware based or software based depending on usage.

• Without firewall, network becomes open and easy target for attackers.

• Almost every organisation uses firewall as first layer of security.

4 . What is a Load Balancer and why scalable systems need it?

A load balancer is a networking component that distributes incoming traffic across multiple servers. Instead of sending all requests to one server, it spreads the load so that no single server gets overloaded. This helps systems handle more users and requests smoothly, which is very important when an application starts growing and gets more traffic.

• Load balancer receives requests from users and forwards them to different servers.

• It helps in improving performance and response time of the system.

• If one server goes down, load balancer can redirect traffic to other working servers.

• This makes the system more reliable and fault tolerant.

• Scalable systems needs load balancer to handle high traffic without crashing.

5. How all these devices work together in a real-world setup?

Imagine a company office where many employees are using internet, accessing files and working on an internal application. All the computers are connected to one network and users expect fast and secure access all the time. To make this possible, different networking devices are used together and each one handles a specific job in the network.

• A switch connects all employee systems and helps them communicate inside the local network.

• A firewall is placed between the office network and internet to block unwanted or harmful traffic.

• A load balancer manages incoming requests and sends them to different servers evenly.

• If one server fails, load balancer redirects traffic to other servers.

This setup keeps the network secure, fast and reliable for daily usage.

Head Out To Next Article To Read More.

2 Explain each device in isolation with a simple responsibility-first approach.

Here Are The Points That Explain How Things Work

Networking Devices and Their Responsibilities (Simple View)

Internet connectivity works because different devices handle different jobs. Each device has a clear responsibility and does not try to do everything. Understanding them one by one makes networking much easier instead of confusing.

Internet Service Provider (ISP)

ISP is the company that provides internet connection to homes and offices. It acts as the starting point of internet access. Without ISP, your network will stay local only.

Modem

Modem’s main responsibility is to convert signals from ISP into digital data that computers can understand. It acts like a translator between internet line and your network. Without modem, router cannot receive internet.

Router

Router decides where the data should go inside the network. It connects your local network to the internet and routes traffic to correct device. Router also allows multiple devices to share one internet connection.

Switch

Switch is used to connect multiple devices inside a local network. Its responsibility is to send data only to the correct device instead of everyone. This makes internal communication faster and clean.

Firewall

Firewall’s job is to protect the network from unwanted access. It checks incoming and outgoing traffic and blocks suspicious data. Firewall acts like a security guard for the network.

Load Balancer

Load balancer distributes traffic across multiple servers. Its responsibility is to avoid overloading a single server. This helps systems stay available even during high traffic.

3.Clearly differentiate between similar devices (hub vs switch, router vs modem)

These Are Day To Day Devices That Help Us To Find The Internet & Use It.

Here Are The Points To Understand A Table Wise Structure to Decode Everything.

Difference Between Hub and Switch.

Difference Between Router and Modem

4 . Use real-world analogies (Small Company Analogy)

Here We Can See The Working Of Small Company.

Internet Connection (ISP to Office)

In this setup, internet starts from the ISP and reaches the company through a physical connection. This is the entry point of internet into the office network. Without this connection, the company network will only work locally and cannot access online services.

Modem

The modem is responsible for converting the signals coming from the ISP into digital data. Computers and networking devices cannot understand raw ISP signals directly. So modem acts as a translator between internet line and office network.

Router

Router connects the office network to the internet and decides where the data should go. When employees access websites or applications, router routes the requests correctly. It also allows multiple devices to share the same internet connection.

Firewall

Firewall is placed between the router and internal network for security purpose. It checks incoming and outgoing traffic and blocks suspicious or unauthorised access. This helps protect company data from external attacks.

Switch

Switch connects all employee systems like computers, printers and internal devices. Its job is to send data only to the required device instead of broadcasting everywhere. This keeps internal communication fast and organised.

Load Balancer and Servers

For company applications, multiple servers are used instead of a single server. Load balancer sits in front of these servers and distributes incoming requests evenly. This prevents server overload and ensures applications remain available even during high usage.

5. Show where these devices sit in a typical system architecture

You Can See The Diagram Now Read Explaination.

Internet (Users and External Access)

In this figure, users from outside the company access applications through the internet. All requests originate from here and are treated as untrusted. Because of this, traffic coming from internet is always checked before entering the company network.

Modem

Modem is placed at the edge of the company setup. It receives the internet connection from the ISP and converts signals into digital data. This allows internal networking devices to understand incoming data.

Router

Router sits just after the modem in the architecture. It connects the company’s internal network to the internet. Router manages traffic direction and helps multiple internal devices share the same internet connection.

Firewall

Firewall is positioned between router and internal company network. Its responsibility is to filter incoming and outgoing traffic. This layer protects company systems from unauthorised access and external threats.

Switch (Office Network Layer)

Switch is placed inside the office network. It connects employee computers, printers and internal systems. Switch ensures data reaches the correct device and keeps internal communication fast.

Load Balancer

Load balancer sits in front of the company servers. All application requests first reach the load balancer. It distributes traffic evenly across servers so no single server gets overloaded.

Application Servers

These servers handle company applications and user requests. Multiple servers are used for better performance and availability. If one server fails, others continue working.

Internal Data Storage

Data related to company operations is stored at the backend. Access to this layer is limited and controlled. This helps keep sensitive company data safe.

6. Keeping the explanation hardware-focused but relevant for software engineers

Keeping The Explaination In Point Wise Way.

Internet (External Hardware Side)

In this setup, internet is the external hardware level where all user requests starts. From a software engineer view, this is where API calls and HTTP requests are coming from. Hardware wise, this part is totally outside company control so it is treated as unsafe.

Modem

Modem is a physical hardware device placed at the entry of the company network. Its only job is to convert ISP signals into digital data that routers and systems can understand. Even if your software is perfect, without modem data will never reach your system.

Router

Router is a core networking hardware device that decides where packets should go. It handles IP addressing and routing tables. For software engineers, router decides how your backend server actually recieves the request from internet.

Firewall

Firewall is a dedicated security hardware sitting between router and internal network. It blocks unauthorised traffic before it even touches your application. This is why sometimes backend APIs fail even when code is correct, firewall rules may block it.

Switch (Internal Hardware Layer)

Switch is internal networking hardware used to connect multiple machines. It works using MAC address and sends data only where needed. From software side, switch ensures low latency communication between services running on different machines.

Load Balancer (Hardware Entry for Apps)

Load balancer is often a physical hardware appliance in small companies. All user traffic hits this device first before reaching servers. For software engineers, this affects session handling, request routing and scalability logic.

Application Servers (Physical Machines)

These are actual hardware machines where backend code runs. CPU, RAM and disk directly affect application performance. If hardware resources are weak, even optimized code will struggle.

Data Storage Hardware

Data is stored on dedicated storage machines or disks. Access to this hardware is limited for security. For software engineers, slow disks or hardware failure can cause major app issues even if queries are written properly.

7 .Ending by connecting these concepts to backend systems and production deployments

Connection to Backend Systems

All these hardware devices directly affect how backend systems behave in real world. When a user hits an API, the request does not magically reach the backend code. It travels through modem, router, firewall, switch and load balancer before touching the server where backend is running. If any hardware layer is slow or misconfigured, backend response will also feel slow even if code is correct.

Role in Production Deployments

In production deployment, backend applications are not run on a single machine. Multiple physical servers are used for reliability and scale. Load balancer decides which server will handle the request, while firewall controls which APIs are allowed from outside. This is why backend engineers must understand hardware flow, otherwise debugging production issues becomes very hard.

Why Software Engineers Should Care

Many production bugs are not code bugs but infra or hardware related. API timeout can be due to firewall rules, server crash can be due to hardware overload, and slow response can be due to poor load balancing. Knowing where devices sit helps backend engineers write better scalable and fault tolerant systems.

Final View

Backend systems and production deployments work on top of networking hardware. Code runs on machines, machines sit behind switches, switches behind firewalls, and everything depends on proper routing and balancing. Understanding this full picture helps software engineers move from local coding to real production systems confidently.

Internet (External Users)

In the 2nd figure, all users access the company applications from internet. Requests like website access or API calls start from here. Since this is outside the company, traffic from internet is considered unsafe by default.

Modem

Modem is the first hardware device inside the company boundary. It recieves the connection from ISP and converts signals into digital data. This makes the internet usable for internal networking devices.

Router

Router is placed after the modem in this setup. It connects the company network to internet and manages routing of packets. From backend view, router decides how user requests actually reaches company servers.

Firewall

Firewall comes next in the flow and acts as a security checkpoint. It filters all incoming and outgoing traffic based on rules. Many times backend issues happens here if ports or IPs are blocked by firewall.

Switch (Internal Office Network)

Switch connects employee systems, internal tools and server machines. It handles internal traffic using MAC addresses. This ensures fast communication between office devices and backend servers.

Load Balancer

Load balancer sits in front of application servers in the 2nd figure. All user requests first hit this device. It distributes traffic evenly so one server does not get overloaded.

Application Servers

These are physical machines where backend code is deployed. They process requests and send responses back through the same flow. Multiple servers are used for scalability and fault tolerance.

Data Storage Systems

Data is stored at backend storage level. Direct access from internet is not allowed. Application servers communicate with storage internally for security and performance reasons.

2. Hub vs Switch packet broadcast comparison

Explanation According to the Diagram (Hub vs Switch)

In the left side of the diagram, a hub is shown in the center with many devices connected to it. One device is marked as sender and all other devices are receivers. When the sender sends a packet, the hub does not know who the actual receiver is. So the hub sends the same packet to all connected devices (A, B, C, D, E, F, G, H). Even devices that are not supposed to get the data will recieve it. This is why many arrows are shown going out from the hub to every device.

In the right side of the diagram, a switch is shown in the center. Here also one device is sender, but when it sends a packet, the switch checks the destination address. The switch already knows which device should recieve the packet. So it sends the packet only to device C*, which is the intended receiver. Other devices like A, B, D, E, F, G, H do not get the packet at all. This is why only one arrow is highlighted in the switch diagram.*

In this diagram, both hub and switch are shown connecting multiple devices in a local network. One device acts as sender and others act as receivers. The main purpose of the diagram is to show how data packets are handled differently by hub and switch when a sender sends data. Even though both look similar in connection, the way data flows is completely different.

Difference Between Hub and Switch (Based on Diagram)

3. Firewall placement in a network How It Works.

Internet (Untrusted Zone)

In the 2nd figure, internet is shown as the outer most part of the network. All user requests and traffic comes from here. Since this area is outside the company, it is always treated as untrusted and risky.

Modem and Router Layer

After internet, the connection reaches the modem and router. Modem converts ISP signals and router manages routing. At this stage, traffic is still not allowed to directly reach company systems, it only prepares the data to move forward.

Firewall Placement

Firewall is placed after the router and before the internal company network in the 2nd figure. This position allows firewall to inspect all incoming and outgoing traffic. Any unauthorised request is blocked here before it can reach office devices or servers.

Internal Network (Trusted Zone)

Behind the firewall lies the internal network which includes switches, employee systems and servers. Because firewall filters traffic, this zone is considered more trusted. Only allowed data is permitted to enter this part of the network.

Servers and Applications Protection

In the figure, servers are placed behind the firewall. This ensures backend systems are never directly exposed to internet. Even if someone targets the server, firewall rules stop access unless explicitly allowed.

4. Load balancer distributing traffic across multiple servers.

Real World Load Balancing Is Distributed In This Way.

5. End-to-end network architecture of a web application

This Diagram Explains How The Web App Works.

1. DNS (Domain Name System)

DNS is the very first step when a user opens a website. When user types a domain name in browser, DNS converts that name into an IP address. Without DNS, browser would not know where the web application is hosted. This step happens before any request reaches the server.

User’s Browser

The browser is where the request is created. User actions like clicking buttons or loading pages generate HTTP requests. Browser sends these requests to the server and also receives responses like HTML, CSS, JS and data.

2. Load Balancer

After DNS resolution, the request reaches the load balancer. Load balancer is the main entry point of the application. It distributes incoming traffic across multiple web app servers. This prevents one server from getting overloaded and helps scale the application.

Web App Servers

Web app servers contain the actual backend code. These servers handle authentication, business logic and API processing. Multiple servers are used so that application remains available even if one server fails.

4. Database

Database stores all important application data like user info, orders and records. Web app servers communicate with database to read and write data. Database is not directly exposed to users for security reasons.

5. Caching Service

Caching service is used to store frequently accessed data in memory. This reduces load on database and improves response time. Instead of hitting database every time, app server first checks cache.

6a. Job Queue

Job queue is used for background tasks. Tasks like sending emails or processing large data are added to queue. This helps keep main application fast and responsive.

6b. Job Servers

Job servers pick tasks from job queue and execute them. These tasks run asynchronously and do not block user requests. This is very important for scalable systems.

7. Full Text Search Service

This service is used for search functionality. It allows fast searching across large datasets. Instead of querying database directly, search queries are handled by this dedicated service.

8. Services (Microservices / External Services)

Services represent additional components or microservices. These can be payment services, notification systems or third-party APIs. Web app servers communicate with these services as needed.

9a. Data Firehose

Data firehose collects application events and logs. It streams data continuously for analytics or monitoring. This data is not used for user requests but for system insights.

9b. Copy Data

Data is copied from firehose to storage systems. This allows long-term analysis and reporting. Copying happens asynchronously.

9c. Data Warehouse

Data warehouse stores processed analytics data. It is used for reporting, dashboards and business intelligence. Normal application flow does not depend on this layer.

10. Cloud Storage

Cloud storage is used to store static files like images, videos and backups. Web app servers upload files here and users download them when needed. This reduces load on app servers.

11. CDN (Content Delivery Network)

CDN serves static content from locations closer to users. Instead of fetching files from main server every time, CDN delivers cached content. This improves speed and reduces latency.

Overall Flow Summary

User → DNS → Load Balancer → Web App Servers → Cache / Database / Services
Static content → Cloud Storage → CDN → User
Background work → Job Queue → Job Servers
Analytics → Firehose → Data Warehouse

Why This Architecture Is Used

This architecture supports scalability, security and performance. Each component has a single responsibility. Backend engineers must understand this flow because many production issues are caused by caching, load balancing or networking, not just code bugs.

Before diving into networking or concepts of networking did you ask yourself what’s the term internet is?

why it is internet & why is it important.

Well basically the internet was used in late 1970’s it was used as to connect as One big machine to another big machine sharing computing power it was mainframe back then as connection would go from cities to states or states to cities mainly only available for the scientists for scientific research mainly controlled by the government it was not available for civilians not for the public purpose.

It was mainly for research & researchers.