Overview

3.1. Overview#

In this section, you will be introduced to the basic concepts of network protocols and the four-layer TCP/IP model that helps computers and devices communicate over the internet. Understanding these concepts is important because they form the foundation of how the internet works. Just like how people follow rules and steps to hold a conversation, computers and networks follow specific protocols and work in layers to send data efficiently across the internet.

By the end of this section, you will be able to explain:

What a network protocol is and why it is necessary
How the four layers of the TCP/IP model work together to deliver data

3.1.1. Network Protocols#

A network protocol is a set of rules or standards that define how data is transmitted and received between devices on a network. Protocols make sure that devices “speak the same language” when they exchange data. For example different devices such as computers, phones, and servers can communicate and understand each other, even if they are built by different manufacturers.

Protocols exist for many different purposes and operate at different levels of abstraction. Common examples are:

Internet Protocol (IP) is the protocol that enables devices to address each other on the network.
Transmission Control Protocol (TCP) is the protocol used to ensure data packets are delivered correctly.
HTTP is a protocol used to transfer web data such as HTML files.

3.1.2. The TCP/IP Layer Model#

The TCP/IP model is a framework that organizes how data is sent and received over the internet. It breaks down the complex process of data communication into four distinct layers, each responsible for different tasks. Think of it like building a house: you need different teams (plumbers, electricians, builders) working on specific parts, but they all contribute to the final product.

Here’s an overview of the four layers of the TCP/IP model:

Application Layer is the top layer where user interaction happens. The Application Layer defines how data is presented to the user and which protocols are used for different types of communication, like web browsing, file transfer, or email. For example, when you use a web browser, you’re interacting with the HTTP protocol, which is part of this layer.

Example: When you type google.com.au into your browser, the Application Layer handles how the request is sent using the HTTP protocol.
Transport Layer ensures that data is delivered reliably and in the right order. It manages the communication between two devices using protocols like TCP (Transmission Control Protocol). TCP ensures that data packets arrive correctly.

Example: When you send a message, TCP breaks it into smaller data packets and ensures that each packet reaches the recipient and is reassembled in the correct order.
Internet Layer is responsible for moving data packets across different networks and ensuring they reach the right destination. This is where IP addresses come into play. The Internet Layer uses the Internet Protocol (IP) to label each packet with a source and destination address.

Example: When you visit a website, the Internet Layer ensures that your request (as data packets) is sent to the correct server using IP addresses.
Network Access Layer is the bottom layer and is responsible for physically sending data over the network. It includes the hardware, such as Ethernet cables or Wi-Fi signals, and deals with how data is transmitted between your device and the router or modem.

Example: When you connect to the internet through Wi-Fi, the Network Access Layer manages how your device sends data to the router, which then sends it out onto the internet.

Attention

We won’t be covering the Network Access Layer.

3.1.3. Glossary#

Application Layer#: The Application Layer is where users interact with the internet, using protocols like HTTP for websites and SMTP for emails to send and receive data through apps like browsers or email clients.
Network Access Layer#: The Network Access Layer is responsible for the physical transmission of data, using devices like routers and cables to send data over networks like Ethernet or Wi-Fi.
Network Protocol#: A network protocol is a set of rules that allows devices to communicate over a network, ensuring data is transmitted and received correctly. Examples include HTTP, TCP, and IP.
TCP/IP model#: The TCP/IP model is a framework that organizes how data is sent over the internet, dividing the process into four layers to ensure reliable and efficient communication.
Transport Layer#: The Transport Layer ensures that data is delivered reliably between devices by breaking it into packets, sending them, and reassembling them correctly at the destination.
Internet Layer#: The Internet Layer handles the routing of data packets across different networks, ensuring that they reach the correct destination using IP addresses.