The Reference
Model for Open Systems Interconnection (OSI) was developed
by ISO (International Organization for Standardization)
as a reference model for the architecture of computer
communications protocols.
The Reference Model contains seven
layers:
Layer
Function
7
Application
Provides means for the application
process (users) to access the OSI environment.
6
Presentation
Provides independence to
the application processes for different data representation
(syntax).
5
Session
Provides means to organize
and to synchronize the dialogue and to manage
the data exchange. Provides means to establish,
maintain and terminate a session.
4
Transport
Provides transparent and
reliable transfer of data between the higher layers.
Provides functions as end-to-end flow control
and error correction.
3
Network
Provides to the higher layers
independence from routing and relay consideration
associated with the establishment and operation
of a given network connection. Provides means
to establish, maintain, and terminates network
connections.
2
Data Link
Provides functional and procedural
means for reliable transfer of data over the physical
link.
1
Physical
Provides mechanical, electrical,
functional and procedural means to activate, maintain,
and de-activate physical connections for bit transmission
over the physical medium.
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