OSI Model Overview

Introduction

• OSI stands for Open Systems Interconnection.
• Conceptual framework for how applications communicate over a network.
• Comprises seven layers to help users identify processes within a networking system.

OSI Model Layers

• Layers are described from top to bottom:
  1. Application Layer (Layer 7):
     • Interface for end-users.
     • Provides network services like HTTP for web browsers.
     • Other examples: Office Outlook, Skype.
  2. Presentation Layer (Layer 6):
     • Manages syntax processing and data format conversion.
     • Responsible for encryption and decryption.
  3. Session Layer (Layer 5):
     • Handles the management of connections between devices.
     • Supports authentication and reconnection after interruptions.
  4. Transport Layer (Layer 4):
     • Transmission of data across network connections.
     • Coordinates data flow, speed, and direction using protocols like TCP and UDP.
  5. Network Layer (Layer 3):
     • Routes data and handles logical to physical address mapping.
     • Uses IP and ARP.
  6. Data Link Layer (Layer 2):
     • Often divided into MAC and LLC sublayers.
     • Manages physical addressing methods and error checking.
  7. Physical Layer (Layer 1):
     • Deals with electrical and physical aspects of the network.
     • Includes cables, connectors, and wireless frequencies.

Practical Application

• OSI model aids developers and vendors in creating compatible communication products and software.
• Understanding the model assists in troubleshooting and identifying compatible protocols and devices.

Summary

• The OSI model is essential for understanding network communications and developing interoperable technology solutions.