Session, presentation, and application layers: Analyse the functions and services of the session, presentation, and application layers of the open system.

Did you know that communication over a computer network is a complex process that involves several different layers of technology? In this lesson, we're going to delve deep into three of these layers – the Session, Presentation, and Application layers – that form part of the open systems interconnection (OSI) model.

Understanding the Open Systems Interconnection (OSI) Model

Before we dive into the specifics of the Session, Presentation, and Application layers, it's important to understand the context in which they exist. The OSI model is a conceptual framework that standardizes the functions of a communication system into seven distinct categories or 'layers'. These layers are, from lowest to highest: Physical, Data Link, Network, Transport, Session, Presentation, and Application.

Diving into the Session Layer 💻

The session layer, also known as layer 5, is responsible for establishing, managing, and terminating connections between applications. This ensures that the data intended for a specific application reaches that application and that the application is ready to receive the data.

For example, when you're video conferencing with a colleague, the session layer sets up the connection between your video conferencing application and theirs, manages the data transfer during the call, and then terminates the connection once the call ends.

Unpacking the Presentation Layer 🎁

Next up is the presentation layer, or layer 6. This layer takes care of the translation of data between the network and the application. This includes tasks like encryption and decryption, compression and decompression, and the translation of network data into a format that the application can understand.

Here's a simple way to think about it: If you're sending an encrypted email, the presentation layer is responsible for encrypting the text of your email into a format that can be sent over the network, and then decrypting it back into readable text when it reaches its destination.

Exploring the Application Layer 📱

Finally, we reach the application layer - layer 7. This is the layer that interacts with software applications to implement network services. This could be services like file transfers, email, network software operations and more.

For instance, when you use your web browser to visit a website, the application layer is what enables your browser to send a request to the web server and display the website on your screen.

Common Protocols and Applications for Each Layer

Each of these layers uses various protocols to perform their functions. For example, the Session layer uses protocols like NFS, SQL, and RPC. The Presentation layer uses protocols like TLS, SSL, and MIME, and the Application layer uses protocols like HTTP, FTP, and SMTP.

In conclusion, the Session, Presentation, and Application layers of the OSI model play crucial roles in data communication and computer networking. Each layer has unique functions and uses different protocols to ensure smooth and secure data transmission.