Introduction

We discussed how the Internet works in our previous blog ie. Insides of the Internet: Let's Explore the Journey of Your Data.But to simplify things for developers and others, there are conceptual frameworks that break down the entire process of internet communication into layers. This layered structure allows each part of the communication process to be examined individually, making it easier to identify and fix problems.

This is where models like the OSI Model and the TCP/IP Model come in. They provide a structured way to understand how data travels over the internet—from your device to servers and back—step by step.

Before diving directly into the Internet protocols first,

In this blog, we’ll first explore the OSI Model, which serves as a conceptual guide. Then we’ll look at the TCP/IP Model, which is the practical framework used in real-world Internet communication. Finally, we’ll dive into the specific internet protocols (like HTTP, TCP, IP, DNS, etc.) and explain how they work at different layers.

So, let’s start….

How the Internet Works (Recap / Overview)

Before diving deeper into protocols and layers, let’s quickly recap how the internet works — in simple, layman's terms:

You type a URL or search a keyword
- For example, you enter www.google.com in your browser.
The request goes to the DNS (Domain Name System)
- DNS acts like the internet’s phonebook. It finds the IP address linked to that domain name.
DNS finds the IP of the server
- Instead of remembering complex numbers like 142.250.68.78, we just use names like google.com. DNS translates it for us.
Your request travels through various networks
- Routers and switches forward your data packet across different devices and networks to reach the destination server.
The server receives the request and sends back the data
- The server processes your request (e.g., search results, a webpage, a video) and sends the data back in small packets.
Your browser displays the result
- All packets are reassembled in your browser, and voilà — the webpage appears on your screen!

Why We Need Conceptual Models

Now you might think — if we already understand how the internet works at a basic level, why do we need conceptual models like the OSI or TCP/IP?

The answer is simple: internet communication is incredibly complex. To manage this complexity, we need a clear structure.

Here’s why these models are essential:

Internet communication is complex
Billions of devices talk to each other globally — across different networks, hardware, and software systems. Without structure, management is very difficult.
Developers and engineers need a roadmap
Conceptual models provide a standardized way to design, build, and fix networks. They help identify where something went wrong — layer by layer, no need to just hit and try to identify errors.
They introduce the idea of layered architecture
Instead of treating the internet as one big mystery, these models break it down into smaller, manageable pieces — called layers. Each layer has its own job and communicates with the layer above and below it.

Think of it like building a house: you just don’t start building the roof. You first lay the foundation, put up walls, then the roof — each step in order, layer by layer not in random way.

The OSI Model – 7 Layers of Communication

Now we are ready to study the Models let’s start with OSI(Open Systems Interconnection) Model. This model consists of 7 layers— Application Layer, Presentation Layer, Session Layer, Transport Layer, Network Layer, Data Link Layer, and Physical Layer.

OMG… that many layers… Don’t worry let’s understand each layer by the analogy of gifting:

1. Application Layer
  - You choose a gift and write a message.
  - Real scenario: You type a message or open a website using apps like WhatsApp, Gmail, or Chrome.
  1. Presentation Layer
    - You wrap the gift neatly.
    - Real scenario: The data is formatted — e.g., text is converted to ASCII, images are compressed, and encryption like SSL/TLS is applied.
  2. Session Layer
    - You call your friend and agree on when to meet.
    - Real scenario: A session is started between your device and the server — like logging into Zoom or Gmail.
  3. Transport Layer
    - You choose a courier and add tracking.
    - Real scenario: Data is broken into packets and assigned ports using TCP (for reliability) or UDP (for speed).
  4. Network Layer
    - The courier plans the best route.
    - Real scenario: IP protocol finds the best path for data to travel through the internet to the destination IP address.)
  5. Data Link Layer
    - The gift is loaded onto the delivery van.
    - Real scenario: Data is framed into bits, MAC addresses are attached, and it's sent through routers and switches on a local network.
  6. Physical Layer
    - The van drives over roads and delivers it.
    - Real scenario: Data is transmitted as electrical signals, light pulses, or radio waves through cables, fiber optics, or Wi-Fi.

Hope, now you can understand the OSI model Model well.

The TCP/IP Model – The Real-World Framework

Now as we understand the OSI model, let’s dive into the TCP/IP Model. This model consists of 4 layers — Application Layer, Transport Layer, Internet Layer, and Link Layer.

Don’t worry, it’s simpler than it sounds. Let’s again break it down with a fun gifting analogy to make things simpler:

Application Layer
- You choose a gift and write a message.
- Real scenario: You type a message or visit a website using apps like WhatsApp, Gmail, or Chrome. This is where the user interacts directly with the network.
Transport Layer
- You choose a courier and add tracking.
- Real scenario: Data is broken into smaller packets, and reliable delivery is ensured using TCP (Transmission Control Protocol) or UDP (User Datagram Protocol) for faster but less reliable transmission.
Internet Layer
- The courier plans the best route.
- Real scenario: The IP (Internet Protocol) decides the best route for your data to travel across the internet, ensuring it reaches the correct destination IP address.
Link Layer
- The gift is loaded onto the delivery van.
- Real scenario: This layer handles how data physically travels across the network. Whether it's over Ethernet, Wi-Fi, or fiber optics, this layer ensures the data is framed and transmitted through routers and switches on the local network.

Now you can see how each layer of the TCP/IP Model works together to deliver data — just like sending a well-packed gift to a friend!

Why TCP/IP If OSI already exists

You might ask — why are we learning about another model (TCP/IP) when the OSI model already explains everything so well?

That’s a great question!

Here’s the simple answer:

OSI is a theory, but TCP/IP is used in real-life
- OSI model is a concept — it shows us how data should flow step by step.
- But OSI was never fully used in the real world.
- TCP/IP model is the one that actually runs the internet today.
- All websites, apps, and online services use TCP, IP, HTTP, DNS, and other protocols from this model.
OSI is for understanding, TCP/IP is for working
- OSI model is good if we want to teach and explain the complete depth. It's like a blueprint for understanding how data flows across a network — layer by layer. It helps in teaching, designing, and troubleshooting network systems.
- TCP (Transmission Control Protocol) is an actual protocol used in the real world. It works with IP in the TCP/IP model, which is the foundation of the modern internet. The TCP/IP model has only 4 layers (somewhat similar to OSI but more practical). It’s not just a concept — it's the actual set of rules and technologies your computer uses to send/receive data.
- Think of TCP/IP as the "real engine" that runs the internet, while OSI is the instruction manual explaining how engines should ideally work in "ideal design".

So why do we learn both?

We learn OSI to understand the process clearly,
and we learn TCP/IP because it’s how the internet really works.

Summarized difference between OSI and TCP/IP

Here is the summarized difference between OSI and TCP/IP Models:

OSI Model	TCP/IP Model
Consists of 7 layers	Consists of 4 layers
It is the instruction manual explaining how engines should ideally work in "ideal design"	It is the "real engine" that runs the internet
Helps in teaching, designing, and troubleshooting network systems.	It’s not just a concept — it's the actual set of rules and technologies your computer uses to send/receive data.

Hope this summarized table may help you.

Internet Protocols by Category and Layer

Now we’re at the point where we can talk about protocols.

Think of protocols as the rules that guide everything happening in the world of the internet. Without these rules, nothing would make sense, and things wouldn’t be standardized — everything would be a mess! Protocols help keep things running smoothly, making sure devices understand each other and data travels properly.

Learning about all the protocols at once can be confusing, so to make it easier, we’ll break them down by the layers of the TCP/IP model. This way, we can focus on the protocols used in each step of the communication process.

Let’s dive in and check out the protocols for each layer!

Communication Protocols

These are the basic rules that help devices communicate with each other on the internet. Think of them as languages that devices speak to understand each other.

IP (Internet Protocol)

Internet Protocol — assigns IP addresses to devices, guiding data to the correct destination.
Analogy: Like the address on a letter, it tells where the data should be sent.
TCP (Transmission Control Protocol)
Transmission Control Protocol — makes sure the data arrives reliably and in the right sequence.

Analogy: Imagine a postman who checks if each part of a message is delivered correctly and in the right order.
UDP (User Datagram Protocol)
User Datagram Protocol — used for faster, but less reliable data transmission, like video streaming or online games.

Analogy: Like sending a postcard — it's quicker, but you don’t know if it’s delivered correctly.
ARP (Address Resolution Protocol)
Address Resolution Protocol — helps find the physical address (MAC address) of a device using its IP address.

Analogy: Think of it as a directory that maps names (like people’s names) to addresses (like street addresses).
ICMP (Internet Control Message Protocol)
Internet Control Message Protocol — used to send error messages and check the status of devices on a network (e.g., "Is the server up?").

Analogy: It’s like sending a "delivery failure" notice when something goes wrong.

Application Layer Protocols

These protocols are used by applications (like browsers and email clients) to communicate with the Internet.

HTTP (Hypertext Transfer Protocol)
Hypertext Transfer Protocol — the protocol for loading websites.

Analogy: Like the language used to speak between your browser and a website.
HTTPS (Hypertext Transfer Protocol Secure)
Hypertext Transfer Protocol Secure — the secure version of HTTP, often used for online banking, shopping, etc.

Analogy: Like HTTP, but with a secure lock to make sure no one can peek at what you're doing.
DNS (Domain Name System)
Domain Name System — translates domain names into IP addresses.

Analogy: Think of it as a phonebook that converts website names (like www.example.com) into an IP address.
FTP (File Transfer Protocol)

File Transfer Protocol — used for transferring files between computers over a network.
Analogy: Like sending a package between computers.
SMTP (Simple Mail Transfer Protocol)
Simple Mail Transfer Protocol — used to send emails from one server to another.

Analogy: The postman for sending emails.
IMAP (Internet Message Access Protocol)
Internet Message Access Protocol — used for accessing email messages stored on a server.

Analogy: Like storing your mail at the post office and picking it up when you want.
POP3 (Post Office Protocol 3)
Post Office Protocol 3 — used to download emails from a server to your local device.

Analogy: Like downloading all your letters to your mailbox.

Security Protocols

These protocols are used to ensure that communication is secure.

TLS/SSL (Transport Layer Security / Secure Sockets Layer)
Transport Layer Security / Secure Sockets Layer — encrypts data between your browser and the server for secure communication (e.g., HTTPS).

Analogy: Like locking your mailbox so that only you can read the mail.
IPSec (Internet Protocol Security)
Internet Protocol Security — secures internet protocol communications by encrypting and authenticating data at the IP layer.

Analogy: Like sealing the envelope so no one can open it while it's on its way.

Routing Protocols

These protocols help direct data to its correct destination across the internet.

BGP (Border Gateway Protocol)
Border Gateway Protocol — used by routers to exchange routing information between different networks (especially for larger networks like the Internet).

Analogy: Think of it like highway signs that guide data from one network to another.
OSPF (Open Shortest Path First)
Open Shortest Path First — a routing protocol used within large enterprise networks to find the best path.

Analogy: Like a GPS that helps find the quickest route for data.
RIP (Routing Information Protocol)
Routing Information Protocol — helps routers in a network find the best path to send data.

Analogy: Similar to OSPF, but it works on simpler and smaller networks.

Conclusion

We’ve walked through the TCP/IP model, the different layers, and the essential protocols that make the Internet function smoothly. From the moment you send a message, browse a website, or watch a video, these protocols are working behind the scenes to ensure everything is reliable, secure, and efficient.

Why Understanding Protocols Matters:

Efficiency: Protocols make sure data gets to the right place, in the right way, without errors.
Security: Protocols like TLS/SSL and IPSec protect your data from being accessed by unauthorized parties.
Structure: Models like TCP/IP provide a clear structure, so developers can troubleshoot, optimize, and build better applications.

Whether you’re a developer working on building the next big app or just someone curious about how the internet works, understanding these protocols will give you deeper insights into how data travels across networks.

The internet may seem like magic, but behind that "magic" is a well-organized, highly structured system of rules and protocols that ensure everything works smoothly.

If you’ve made it this far, you’re now better equipped to understand the complexities of internet communication and how protocols play a crucial role in making it all happen!

From Society to Servers: Join the Journey to Understanding Internet Protocols

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