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The OSI Model

The OSI model was introduced in 1984. Although it was designed to be an abstract model, the OSI model remains a practical framework for today's key network technologies like Ethernet and protocols like IP.

 

Definition: The OSI model ĖOpen System Interconnection model  defines  a set of protocols that allow two different  system to communicate regardless of their underlying architecture . The purpose is to show how to facilitate communication between different system without requiring changes to the logic of  underlying hardware and software.

 

The OSI model is not a protocol it is a model for understanding and designing a network architecture that is flexible , robust and interoperable

 

 

In internetworking  terms itís  a vertical stack of seven layers. The upper layers of the OSI model represent software that implements network services like encryption and connection management. The lower layers of the OSI model implement more primitive, hardware-oriented functions like routing, addressing, and flow control.

In the OSI model, data communication starts with the top layer at the sending side, travels down the OSI model stack to the bottom layer, then traveses the network connection to the bottom layer on the receiving side, and up its OSI model stack.

 

 

 

 

 

  APPLICATION

 
LAYER 7 (UPPER LEVEL)
PRESENTATION
LAYER 6
 
SESSION
LAYER 5
 
TRANSPORT
LAYER4
 
NET WORK
LAYER 3
 
DATA LINK
LAYER 2
 
 
PHYSICAL
 
LAYER 1 (LOWER LEVEL)