The OSI (Open Systems Interconnection) model is a conceptual framework that describes how data is transmitted and received over a network. This model helps us understand the step-by-step process of communication between devices and is divided into seven layers. Each layer performs specific tasks and interacts with the layers directly above and below it.
Key Learning Objectives:
- Understand the purpose of the OSI model.
- Identify and explain the seven layers and their responsibilities.
- Recognize the importance of layered communication in networks.
The Seven Layers of the OSI Model:
- Physical Layer: Responsible for transmitting raw binary data over physical media like cables or wireless signals. It handles bits, not packets or frames.
- Data Link Layer: Manages node-to-node communication. It handles MAC addressing, error detection, and frames. Examples: Ethernet, Wi-Fi.
- Network Layer: Focuses on routing and logical addressing (IP addresses). It determines the best path for data to travel. Example: IPv4, IPv6.
- Transport Layer: Ensures reliable data delivery with protocols like TCP (connection-oriented) and UDP (connectionless).
- Session Layer: Establishes, manages, and terminates sessions between devices. Think of it as a conversation manager.
- Presentation Layer: Formats and translates data for the Application Layer. It handles encryption, compression, and data translation.
- Application Layer: The closest to the user, this layer provides services like email, file transfer, and web browsing. Examples: HTTP, FTP, SMTP.
Key Takeaway:
The OSI model is essential for troubleshooting and designing networks. While not directly implemented in real-world protocols, it offers a standardized way of understanding complex communication systems.