6.6 The OSI Networking Model
The Open Systems Interconnection (OSI) Model is a framework used to understand how different networking protocols interact. It has 7 layers, each with a specific function. Let's explore these layers with examples and relate them to daily life.
Figure 6.12: OSI Model
Layer 1: Physical Layer
The Physical Layer is liable for the actual connection between devices. The process of sending unprocessed data bits via a physical medium is the focus here.
Example: Imagine the hardware that connects computers, like a Network interface cables, repeaters, hubs and connectors.
Did You Know
The Physical Layer includes everything from the cables to the voltage levels used to transmit data!
Layer 2: Data Link Layer
Error detection and correction, as well as node-to-node data transport, are handled by the Data Link Layer. It ensures error-free data transmission from the Physical Layer.
Example: Think of the Data Link Layer as traffic lights at intersections, which manage the flow of cars (data) and prevent collisions.
Class activity
Draw a simple network with devices and label the physical connections and data link layer responsibilities.
Layer 3: Network Layer
The Network Layer is responsible for data transfer between different networks. It determines the best path for data to travel from the source to the destination.
Example: Imagine a GPS system finding the best route for you to travel from home to school.
Tidbits
The Network Layer uses IP addresses to route data between networks!
Layer 4: Transport Layer
The Transport Layer ensures that data is transferred from one process rerunning on source end system to a process souring on destination end system. It manages data flow control and error checking.
Example: Think of the Transport Layer as a delivery service that ensures your package arrives safely and on time.
Did You Know
The Transport Layer uses protocols like Transmission Control Protocol (TCP) to ensure reliable data transfer!
Layer 5: Session Layer
The Session Layer manages sessions between applications. It establishes, maintains, and terminates connections between devices.
Example: Imagine a phone call where the session layer sets up the call, keeps it connected, and ends it when you hang up.
Class activity
Role-play a phone call and discuss how the session is established, maintained, and terminated.
Layer 6: Presentation Layer
The Presentation Layer translates data between the application layer and the network. It formats and encrypts data to ensure it is readable by the receiving system.
Example: Think of the Presentation Layer as a translator converting a book from one language to another so that more people can read it.
Did You Know
The Presentation Layer handles data encryption and compression!
Layer 7: Application Layer
The Application Layer is the closest to the end user. It provides network services directly to applications, such as email, web browsing, and file transfer.
Example: Imagine the Application Layer as a waiter taking your order in a restaurant and bringing your food.
Class activity
List the applications you use daily and identify which rely on the Application Layer for network services.