What is OSI Model ?
OSI model is a network model which is define whole process how communication is possible between two network device. OSI is stands for Open System Interconnection.
It’s is not a physical model, it’s a logical model. It provides a guidelines to developer who are make a applications which is running on a network.
It has 7 layers which is divided into two groups.
- Upper Layers
- Lower Layers
Upper layer shows that ow end points are communicate with each other.
Lower layers are shows that how data is transferred end to end.
1. Upper Layers :-
According to above image users interact with the computer at the Application layer and also that the upper layers are responsible for applications communicating between hosts. None of the upper layers knows anything about networking or network addresses because that’s the responsibility of the four bottom layers.
2. Lower Layers :-
These bottom layers also determine how to rebuild a data stream from a transmitting host to a destination host’s application.
The following network devices operate at all seven layers of the OSI model :-
- Network management stations (NMSs)
- Web and application servers
- Gateways (not default gateways)
- Network hosts
Basically, the ISO is pretty much the Emily Post of the network protocol world. the ISO developed the OSI reference model as the precedent and guide for an open network protocol set. Defining the etiquette of communication models, it remains the most popular means of comparison for protocol suites today.
The OSI reference model has the following seven layers :
- Application layer (layer 7)
- Presentation layer (layer 6)
- Session layer (layer 5)
- Transport layer (layer 4)
- Network layer (layer 3)
- Data Link layer (layer 2)
- Physical layer (layer 1)
Advantages of OSI Model :-
- It divides the network communication process into smaller and simpler steps.
- It allows multiple-vendor development through the standardization of network components.
- OSI model encourages industry standardization by clearly defining what functions occur at each layer.
- It allows various types of network hardware and software to communicate.
- It prevents changes in one layer from affecting other layers to expedite development.