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Behind the Network: A Simple Guide to How the Internet Works

Behind the Network: A Simple Guide to How the Internet Works

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Kartik Ch
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The best way to understand networking is by learning how the internet works. The internet is a magical place where we access endless information, connect with people worldwide, and use apps that make life easier. But how exactly does it all work?

In this blog, we’ll break down how the internet works, focusing on key networking concepts like the OSI model and the TCP/IP model, and how they make it all possible.

The Basics of the Internet

Before we dive into the technical layers, let’s understand the internet’s basic concept. The Internet is a vast network of interconnected devices (computers, smartphones, servers, etc.) that communicate to transfer data. When you browse a website, watch a video, or send an email, data is sent across the internet in small chunks called data packets. These packets travel through various devices, routers, and networks, eventually reaching the right destination.

So, the internet is a huge network that helps devices communicate and deliver required information. It works with the help of a web of cables made of optical fiber through which data is transferred.

Refer to the Submarine Cable Map for a clear idea of the world's major submarine cable systems.

How Data Moves

  • Data is divided into packets: Every information sent over the Internet is broken down into small chunks called packets.

  • Routing the packets: As the packets travel, routers guide them through different networks based on the IP addresses they are targeting.

  • Reassembly: Once the packets reach their destination, they are reassembled into the original data (like an email or a webpage).

Understanding OSI Model: Breaking Down Internet Communication (7 Layers)

The OSI model (Open Systems Interconnection model) is a conceptual framework that helps us understand how computers and devices communicate over a network. It breaks down the complex process of network communication into seven layers, with each layer responsible for a specific part of the communication. These layers work together to ensure smooth data transfer between devices. Here’s a breakdown, starting from the bottom (where the hardware is) to the top (where users interact with the system):

  1. Application Layer (User Interaction):

    • The layer closest to the user. It’s what you directly interact with – like web browsers, email apps, or file-sharing apps. It handles the tasks you use every day.

    • Example: The web browser you use to open websites, or the email app you use to send and receive messages, all operate at this layer.

  2. Presentation Layer (Data Translation):

    • This layer ensures that the data is in the right format and readable by the receiving device (such as converting text, images, or files into a usable form).

    • Example: When your browser receives a web page, it needs to decode and display it properly. The Presentation Layer ensures the data (like HTML or images) is shown correctly on your screen.

  3. Session Layer (Managing Conversations):

    • Manages the "conversation" between devices. It keeps track of the data being exchanged and makes sure both devices are in sync.

    • Example: If you’re video calling a friend, the Session Layer ensures that the call stays active and maintains the connection.

  4. Transport Layer (Reliable Delivery):

    • Ensures that data is delivered correctly and completely. It’s like the "delivery service" that checks whether the data made it safely and in the right order.

    • Example: TCP (Transmission Control Protocol) ensures that when you download a file, it arrives intact. If something goes wrong, it can request a resend of any lost packets.

  5. Network Layer (Addressing & Routing):

    • This layer ensures data can find its way from one device to another, even across different networks. It uses IP addresses (the "address" of a device on the internet).

    • Example: The IP address of your device is like your home address, and the Internet Protocol (IP) decides the best path for the data to reach its destination, even across multiple networks.

  6. Data Link Layer (Data Packaging):

    • This layer ensures data is sent correctly over the connection and handles things like error checking and addressing between devices.

    • Example: When your computer talks to the router over Wi-Fi, it’s using the MAC address (a unique identifier for devices) to ensure the data goes to the right place.

  7. Physical Layer (The Physical Connection):

    • Think of this as the "wires" and hardware that physically connects devices to the internet (like cables, routers, etc.).

    • Example: A Wi-Fi router sends data through wireless signals or Ethernet cables connecting your computer to the internet.

Understanding the TCP/IP Model: A Practical Approach (4 Layers)

The TCP/IP model (Transmission Control Protocol / Internet Protocol) is a simplified version of the OSI model and is the framework used for most modern internet and network communications. It breaks the process into four layers, instead of the seven layers in the OSI model. It is specifically focused on how data is transmitted over the internet.

  1. Application Layer:

    • This is where the apps you use (like web browsers or email) work. It makes sure the app can send and receive data.

    • Example: When you use a web browser like Chrome or Safari to visit websites, or you send an email using Outlook or Gmail, you’re using the Application Layer. This layer takes care of the communication between your app and the internet.

  2. Transport Layer:

    • It makes sure the data is sent correctly and safely from one device to another.

    • Example: If you’re streaming a video or downloading a file, TCP (Transmission Control Protocol) makes sure the data arrives intact. If a piece is missing, TCP will ask for it to be sent again, ensuring everything works smoothly.

    • If you're using UDP (User Datagram Protocol), in case of real-time video calls or online gaming, it sends data quickly. However, it doesn’t care about missing packets. Speed is prioritized over reliability.

  3. Internet Layer:

    • This layer helps figure out the best route for the data to travel and ensures it reaches the right device.

    • Example: our device uses an IP address (like your home address but for devices) to send data to the right place. IP (Internet Protocol) helps figure out the best path to take across different networks and devices, ensuring your data reaches its destination.

  4. Network Access Layer:

    • This layer deals with the connection, like the cables or Wi-Fi that allow data to travel.

    • Example: This is the layer that controls how your device connects to the network, whether you’re using Wi-Fi, Ethernet cables, or cellular data. It ensures the data is sent over the network, whether you're surfing the web or sending a text message.

How Data Travels Across The Internet?

Imagine you want to send a message through an app on your phone. Here’s what happens:

  • The message first goes through the Application Layer where it is prepared to be sent over the internet.

  • It’s broken down into smaller packets at the Transport Layer, and the system makes sure that the message will be delivered correctly.

  • The packets are then routed to their destination at the Internet Layer using the destination’s IP address.

  • Finally, the packets travel over the physical network at the Network Access Layer, whether it’s through Wi-Fi or Ethernet cables, until they reach their destination.

Once the data reaches the receiving device, the process is reversed, and the message is reassembled and displayed on the recipient’s screen.

OSI Model Vs TCP/IP Model

  1. Number of Layers:

    • OSI Model: 7 Layers

    • TCP/IP Model: 4 Layers

  2. Focus:

    • OSI Model: A conceptual framework for understanding network communication, with each layer having specific functions.

    • TCP/IP Model: A practical framework that is used for real-world communication over the internet and networks.

  3. Layer Functions:

    • OSI Model: Has separate layers for presentation (data formatting) and session (connection management). Each layer has a specific task.

    • TCP/IP Model: It combines some of the OSI model's layers, such as the Presentation and Session layers, into the Application layer.

  4. Development:

    • OSI Model: Developed by ISO (International Organization for Standardization) as a theoretical model.

    • TCP/IP Model: Developed by the US Department of Defense to establish the internet protocols.

  5. Layer Names:

    • OSI Model: It includes layers such as Physical, Data Link, Network, Transport, Session, Presentation, and Application.

    • TCP/IP Model: It has simple layers: Network Access, Internet, Transport, and Application.

  6. Protocols:

    • OSI Model: It focuses more on the theory of how data should be transferred across networks, without specifying particular protocols.

    • TCP/IP Model: Designed with specific protocols like TCP, IP, UDP, and HTTP.

  7. Usage:

    • OSI Model: Mostly used for educational purposes and understanding network communication.

    • TCP/IP Model: Used in real-world network communication (like the internet).

Role of IP Address, MAC Address, and DNS

IP Address

Every device on the internet has a unique IP address that identifies it. This is essential for routing data to the correct location.

  • IPv4: A 32-bit address, which gives about 4.3 billion unique addresses.

  • IPv6: A newer 128-bit address format, providing a virtually unlimited number of unique IP addresses.

MAC Address

It is a 48-bit address assigned by the manufacturer such that each device has a unique identifier within a network. Unlike IP addresses, MAC addresses are fixed and do not change.

NOTE: MAC addresses help devices communicate locally, IP addresses are used for routing data across networks, from one device to another, ensuring the data reaches the right destination across the internet.

DNS (Domain Name System)

While IP addresses and MAC addresses are used by computers, humans prefer easy-to-remember domain names like www.google.com. DNS acts as a “phonebook” of the internet, used for translating domain names into IP addresses.

Conclusion: Why Understanding the Internet Matters

In today’s world, understanding how the internet works is crucial. The OSI and TCP/IP models provide a simple framework for how data travels across networks, from your device to remote servers. Whether you're troubleshooting network issues, securing your data, or just curious about how the internet works, these models help.

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