The Open Systems Interconnection (OSI) model is a conceptual framework that helps us understand how networks function. It divides network communication into 7 distinct layers, each with specific responsibilities.
Think of it like a team where each member has a special job to help send your message across the internet!
Click on each layer to learn more about its function and see examples!
The Application layer is the one closest to the end user. It provides network services directly to applications.
The Presentation layer prepares data for the application layer. It's like a translator and formatter.
The Session layer establishes, manages, and terminates connections between applications.
The Transport layer provides reliable data transfer services to the upper layers.
Like a delivery truck with error-checking - ensures packages arrive complete and in order!
The Network layer provides routing and switching technologies, creating logical paths for transmitting data.
Like a postal service sorting facility - determines the best path for your data to travel!
The Data Link layer provides node-to-node data transfer between two directly connected nodes.
Like a traffic light system - controls the flow of data and ensures it moves without collisions!
The Physical layer transmits raw bit streams over a physical medium.
Like roads and highways - provides the actual path for data to travel on!
You compose an email in your email client (like Gmail or Outlook). The Application layer handles the interface between your email application and the network.
Your email is formatted and may be encrypted. If you attached images or files, they're compressed. The Presentation layer ensures your email is in a format that can be understood by the recipient's system.
A connection is established with the email server. The Session layer manages this connection and ensures it remains open until the email transmission is complete.
Your email is divided into smaller packets for efficient transmission. The Transport layer (using TCP) ensures all packets will arrive correctly and in the right order.
Each packet receives IP addressing information to find its way to the recipient's email server. The Network layer determines the best path for each packet to travel.
The packets are prepared for transmission over the physical network. MAC addresses are added to direct the packets to the next physical device (like your router).
The packets are converted to electrical signals (for wired connections) or radio waves (for wireless). These signals travel through cables, Wi-Fi, and other physical media to reach the recipient's email server.
What happens when different layers have problems? Explore these scenarios!
Symptom: You can't connect to any websites or online services.
Possible Layer Problem: Layer 1 (Physical) or Layer 2 (Data Link)
If Layer 1 (Physical) is the problem, there might be a broken cable, unplugged connection, or hardware failure. If Layer 2 (Data Link) is the problem, your device might not be able to communicate with your router.
Symptom: You can browse most websites, but one specific site won't load.
Possible Layer Problem: Layer 3 (Network) or Layer 7 (Application)
If Layer 3 (Network) is the problem, there might be routing issues to that specific website. If Layer 7 (Application) is the problem, the website's server might be down or there could be DNS issues.
Symptom: Your video call keeps freezing or the quality is poor.
Possible Layer Problem: Layer 4 (Transport)
Layer 4 (Transport) manages the flow of data and ensures reliability. Issues here can cause delays, packet loss, or out-of-order delivery, resulting in poor video quality.
Your mission: Diagnose network problems by identifying which OSI layer is causing the issue.
Earn badges for correct diagnoses and become a Network Troubleshooting Expert!
A student is trying to connect to the school Wi-Fi network but can't get online. Their laptop shows it's connected to the network, but web pages won't load. Other students are using the same network without issues.
Let's see how well you understand the OSI model! Answer these questions to test your knowledge.