Seven Layers of the OSI Model

The Seven Layers of the OSI Model

7 Application
Network Process to Application
  • Provides network services processes to application processes (such as electronic mail, file transfer,…)
  • Provides user authentication
6 Presentation
Data Representation
  • Ensures that data is readable by receiving system
  • Formats data
  • Structures data
  • Negotiates data transfer syntax for application layer
  • Provides encryption
5 Session
Interhost Communication
  • Establishes, manages, and terminates sessions between applications
4 Transport
End-to-end Connections
  • Handless transportation issues between hosts
  • Ensures data transport reliability
  • Establishes, maintains, and terminates virtual circuits
  • Provides reliability trough fault detection and recovery flow control
3 Network
Data Delivery
  • Routes data packets
  • Selects best path to deliver data
  • Provides logical addressing and path selection
2 Data Link
Access to Media
  • Defines how data is formatted for transmission and how access to the network is controlled
  • Provides error detection
1 Physical
Binary Transmission
  • Defines the electrical, mechanical, procedural, and functional specifications for activating, maintaining, and deactivating physical link

Encapsulation 7 -> 1
De-Encapsulation 1 -> 7

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