OSI Model

• Open Systems Interconnection (OSI) reference model
  • Seven-layer model
• Describes how applications communicate over the network
• Typically described from top --> down
• Meant to make developing communication products easier

Layers

• Lower two layers form the foundation of the Internet
  • Other protocols deal with specific types of network communication
• Application, Presentation, and Session layers are often intertwined
  • Can be hard to distinguish between them

1. Physical layer
2. Data link layer
3. Network layer
4. Transport layer
5. Session layer
6. Presentation layer
7. Application layer

Protocol Data Unit (PDU)

• Technical name for bits moving from one layer to the next

Computer Science Networking