Lecture Notes: OSI Model

Introduction

• Presenter: John from TryHackMe
• Topic: OSI Model and its importance in networking
• Purpose: Understanding the stages of data handling across a network using the OSI Model as a framework

Task 1: What is the OSI Model?

• OSI Model: Open Systems Interconnection Model
  • A fundamental model used in networking
  • Provides a framework for sending, receiving, and interpreting data
• Benefits:
  • Devices can have different functions/designs but still communicate
  • Ensures data uniformity across networks
• Structure: Consists of 7 layers
  • Layers: Physical, Data Link, Network, Transport, Session, Presentation, Application
• Key Process: Encapsulation

Questions

• OSI in OSI Model stands for: Open Systems Interconnection
• Number of layers: 7
• Term for adding information to data: Encapsulation

Task 2: Layer 7 - Application

• Purpose: Determines how users interact with data
• Examples:
  • Email clients, browsers, FTP servers
  • Use interfaces like GUI (Graphical User Interface)
• Protocols: Include DNS for translating domain names to IP addresses

Questions

• Name of Layer 7: Application Layer
• Technical term for user interface software: Graphical User Interface

Task 3: Layer 6 - Presentation

• Purpose: Standardizes data format
  • Acts as a translator for data between application layer and network
• Functions: Data encryption, format translation

Questions

• Name of Layer 6: Presentation Layer
• Main purpose: Standardization (Translator)

Task 4: Layer 5 - Session

• Purpose: Establishes connection/session between computers
• Functions:
  • Synchronizes computers
  • Divides data into packets
  • Ensures unique sessions for data transmission

Questions

• Name of Layer 5: Session Layer
• Term for established connection: Session
• Term for data chunks: Packets

Task 5: Layer 4 - Transport

• Purpose: Transmits data accurately
• Protocols:
  • TCP (Transmission Control Protocol)
    • Reliable, error-checking
    • Used for file sharing, email
  • UDP (User Datagram Protocol)
    • Faster, no error checking
    • Used for video calls, streaming

Questions

• Name of Layer 4: Transport Layer
• TCP stands for: Transmission Control Protocol
• UDP stands for: User Datagram Protocol
• Protocol for accuracy: TCP
• Protocol indifferent to data receipt: UDP
• Protocol for email clients: TCP
• Protocol for file downloads: TCP
• Protocol for video streaming: UDP

Task 6: Layer 3 - Network

• Purpose: Routing and reassembly of data
• Functions: Determines optimal data paths
• Protocols: OSPF (Open Shortest Path First), RIP (Routing Information Protocol)
• Addresses: Uses IP addresses

Questions

• Name of Layer 3: Network Layer
• Packets take optimal route: Yes
• OSPF stands for: Open Shortest Path First
• RIP stands for: Routing Information Protocol
• Type of addresses: IP addresses

Task 7: Layer 2 - Data Link

• Purpose: Physical addressing for transmission
• Functions: Adds MAC address to data
• Hardware: Network Interface Card (NIC)

Questions

• Name of Layer 2: Data Link Layer
• Hardware for network devices: Network Interface Card (NIC)

Task 8: Layer 1 - Physical

• Purpose: Physical components of networking
• Functions: Uses electrical signals for data transfer
• Components: Ethernet cables

Questions

• Name of Layer 1: Physical Layer
• Number system for signals: Binary
• Cables used: Ethernet cables

Task 9: Practical OSI Game

• Activity: Escape the OSI Dungeon by ordering layers correctly
• Purpose: Reinforce understanding of OSI model layer order

Task 10: Continue Learning

• Suggested Next Step: Join the Packets and Frames room to further understand network data transfer.
• Resources: TryHackMe Discord and subreddit for questions and community support.