3.2. Internet Layer#
In this section, you will learn how computers communicate with each other over the internet and how data is reliably sent from one place to another. Specifically, we will explore key concepts such as data packets, internet protocol (IP), addressing and packet routing. These topics are important because they form the foundation of how the internet works. Whether you’re streaming a video, sending a message, or browsing a website, these technologies are used, ensuring your data gets where it needs to go.
By the end of this section, you will be able to explain:
How data is split into packets and sent across the internet
What IP addresses are and how they identify devices
How packets travel from one device to another
How TCP ensures data is delivered reliably and in the right order
3.2.1. Data Packets#
When data is sent over the internet, it is broken down into smaller pieces called data packets. These packets can be thought of as individual envelopes containing parts of a larger message. For example, if you send an image to a friend, that image is divided into many smaller packets before being sent. Each packet is then sent independently across the internet.
Once the packets arrive at their destination, they are reassembled into the original data, just like putting together the pieces of a puzzle. This method is faster and more reliable than sending the entire image in one go. If a packet is lost or damaged during transmission, only that packet needs to be re-sent, not the whole image.
3.2.2. Internet Protocol (IP)#
Internet Protocol (IP)` is the set of rules that governs how data is sent and
received over the internet. Every device that communicates on the internet uses IP to
exchange data packets. IP is the implementation of of the internet layer. The most
common version of IP today is IPv4, which uses addresses that look like this:
192.168.0.1.
IP is responsible for labeling each packet with important information, including:
The source IP address (where the packet is coming from)
The destination IP address (where the packet is going)
Addressing#
Just like homes have addresses so the postal service knows where to deliver mail, computers and other devices on the internet have IP addresses. An IP address is a unique series of numbers assigned to each device connected to the internet. This address allows devices to find and communicate with each other.
For example, when you visit a website like google.com.au, your computer is actually communicating with a server (a computer that provides web services) that has a specific IP address. While you don’t see the IP address because you typed the domain name (like google.com), behind the scenes, your computer sends data to the server’s IP address, and the server sends the webpage back to your computer’s IP address.
Local and Public IP Addresses#
At home or school, your devices (like your phone, tablet, or laptop) likely have local IP addresses. These are addresses that are only used within your local network. When your data needs to go out onto the internet, it first passes through your router, which has a public IP address that identifies your entire network on the internet.
For example:
Your computer might have the local IP address
192.168.0.10inside your home network.When you visit a website, your router has a public IP address like
203.0.113.5, which is used to send data out to the internet and bring it back to your device.
This system allows multiple devices on your local network to share one public IP address when they access the internet.
Packet Routing#
After data packets are labeled with IP addresses, they need to find their way from the sender to the receiver. This is where packet routing comes in. Routers are devices that sit between different parts of the internet and make sure that data packets are forwarded along the correct path. Think of routers like traffic signals that help direct cars (packets) through the streets (internet) to reach their destination.
Packets don’t always take the same route. Just like a car can take different roads to get to the same place, packets can travel through different routers on their way to their destination. Each router looks at the destination IP address on a packet and decides which path will be the fastest or most efficient.
Even if some parts of the internet are slow or busy, routers will find the best available route to ensure your data arrives as quickly as possible.