OSI Model

•OSI means Open System Interconnect model.
•Developed by the International Organization for Standardization in 1974.
•It consists of seven layers.
•Each layer has a different but specific processing function.


OSI Model Layers

Layer - 7------ Application-------

Layer - 6------Presentation------ ------------> Software Layer

Layer - 5------Session ------------

Layer - 4------Transport-------- ------------Heart of OSI

Layer - 3------Network--------

Layer - 2------Data Link------ ---------------Lower Layer

Layer - 1------Physical---------

Application Layer

Application Layer is responsible for providing Networking Services to the user. It is also known as Desktop Layer. Identification of Services is done using Port Numbers.

Ports are Entry and Exit Points to the Layer

Total No. Ports 0 – 65535
Reserved Ports 0 – 1023
Open Client Ports 1024 – 65535