OSI Model Introduction and Layers

OSI Model - Introduction

• The OSI Model helps understand network functions, web browser operation, internet protocol, and MAC addresses.
• Learning the OSI Model aids troubleshooting and communication with technical personnel.
• The model is a framework to implement protocols in layers with control passed between layers.

OSI Model Layers

• The model conceptually divides network architecture into 7 layers:
  • Application (Layer 7) - Handles user applications, like a web browser
  • Presentation (Layer 6) - Handles data format conversions (e.g., image formats)
  • Session (Layer 5) - Manages connections and how they initiate and close.
  • Transport (Layer 4) - Handles communication between applications, using protocols like TCP or UDP.
  • Network (Layer 3) - Uses logical addresses (e.g., IP addresses) and deals with routing of data.
  • Data Link (Layer 2) - Manages physical addressing schemes, like MAC addresses in ethernet networks
  • Physical (Layer 1) - Responsible for ultimate bit transmission over the network, using electrical voltages, radio frequencies, or infrared/light signals.

OSI Model - Network Architecture

• The OSI model, shown in figure 1.17, defines a networking framework for protocol implementation.
• The layers have a logical progression, with lower layers handling signals and routing, and higher layers handling network requests and responses.
• Layer 1,Physical Layer, is accountable for transmitting digital data bits between devices.
• Layer 2, Data Link Layer, checks for transmission errors and packages bits into frames.
• Layer 3, Network Layer, handles routing via logical addresses (like IP addresses) and translating to physical addresses.
• Layer 4, Transport Layer, delivers data across connections, using protocols like TCP.
• Layer 5, Session Layer, is responsible for how network connections are initiated or terminated.
• Layer 6, Presentation Layer, is the simplest layer in the OSI model, handles data format conversions and encryption/decryption.
• Layer 7, Application Layer, provides network services to end-user applications.

OSI Model - Example (Web Browser)

• A web browser interacts with a web server to retrieve a webpage.
• The browser interacts with the application layer (HTTP) to request a webpage.
• The request travels through Presentation, Session, Transport, Network, Data Link, and Physical layers to reach the server.
• Similar communication occurs for responses received and displayed by the browser.

This quiz covers the OSI Model and its seven layers, facilitating an understanding of network functions, web browsers, and internet protocols. Learning the OSI Model is essential for troubleshooting and effective communication with technical personnel. Test your knowledge of each layer's role within network architecture.