SUMMARY

SUMMARY OSI MODEL

The Open Systems Interconnect (OSI) model has seven layers. This article describes and explains them, beginning with the 'lowest' in the hierarchy (the physical) and proceeding to the 'highest' (the application). The layers are stacked this way:

• Application
• Presentation
• Session
• Transport
• Network
• Data Link
• Physical

The differences between OSI model and TCP/ IP model are:

• OSI is standard legislated by official recognized body (ISO), while TCP/ IP are standard adopted due to widespread use.
• The OSI reference model was devised before the protocols were invented, while in TCP/ IP model, the protocols came first.
• The protocols in the OSI model are better hidden than in the TCP/ IP model and can be relatively easily as the technology changes.
• TCP/ IP are more widespread used than OSI.
• TCP/ IP are simpler than OSI.
• TCP/ IP are not as costly as OSI.
• OSI is more commonly used as teaching aids, while TCP/ IP is more commonly used for internetworking because TCP/ IP protocols suite on which the Internet depends.
• OSI uses Horizontal approach, while TCP/ IP use Vertical approach.
• OSI network layer provides both connectionless and connection-oriented services, while the TCP/ IP internet layer is exclusively connectionless.