OSI Reference Model

Application layer, Presentation layer, Session layer, Transport layer [segment]

Network layer [packets], Data link layer [frame], Physical layer [bits]

APPLICATION LAYER

  • Provides network services to application processes like e-mail, File Transfer, and Terminal Emulation.

PRESENTATION LAYER

  • Data representation
  • Ensures data is readable by receiving system
  • Format of data
  • Data structure
  • Negotiates data transfer syntax for application layer
  • Compression, decompression, encryption and decryption

SESSION LAYER

  • Inter-host communication
  • Establishes, manages, and terminates sessions between applications

TRANSPORT LAYER

  • End-to-end connection reliability
  • Concerned with data transport issues between hosts
  • Data transport reliability
  • Establishes, maintains, and terminates virtual circuits
  • Fault detection and recovery
  • Information flow control

NETWORK LAYER

  • Addresses the best path
  • Provides connectivity and path selection between two end systems
  • Domain of routing

DATA LINK LAYER

  • Access to media
  • Provides reliable transfer of data across media
  • Physical addressing, network topology, error notification and flow control

PHYSICAL LAYER

  • Binary transmission
  • Through wires, connectors, voltages, data rates