ISO 7 Layer Model

The ISO/OSI model describes computer communication services and protocols, without making assumptions concerning:

  • programming language bindings
  • operating system bindings
  • application and user interface issues
  • A model is simply a way of organizing knowledge and provides the common basis for discussion.

    The ISO OSI Reference Model is a layered model - with each layer providing certain services and calling upon the services of other layers.

    7 Application layer

    responsible for managing the communication between the applications

    6 Presentation Layer

    provides common operations on the structure of data being exchanged

  • Syntax Conversion
  • Encryption
  • Compression

    5 Session Layer
  • Provides the control structure for managing communications

  • establishing
  • managing
  • terminating sessions (connections).

    4 Transport Layer
  • Provides reliable transparent data transfer between end points (there may be more than two end points)

  • provide error recovery and flow control.

    3 Network Layer
  • Makes the upper layers independent of the data transmission, switching technologies, and topology of the network

  • determine which path (or pathes) in the network that a given unit of data will take (routing).

    2 Link Layer
  • Provides reliable transfer across the physical links

  • establishes the beginning and end of blocks of data (with synchronization when necessary) [framing];
  • error detection and possibly correction;
  • (link) flow control.

    1 Physical Layer
  • Provides transmission of unstructured bits across the physical medium

  • electrical
  • optical
  • mechanical
  • ...