Open System Interconnection Reference Model (O S I)?

Today we are discus about OSI reference model is a model that is help to understand the network. It is the layered approach to understand the network and easy to troubleshoot. OSI reference model is very much similar the human body. Human body is also a layered approach. For example if anybody feels the pain in his eyes, he should go to the eye specialist not go to the heart specialist and that specialist can easy to understand the disease of eyes and give him the best treatment to him. So the OSI reference model is also helps to troubleshoot the networks and solve the problem.

Layers of OSI reference model

7Layers of OSI reference model are

1.   A       Application

2.   P       Presentation

3.   S       Session

4.   T       Transport

5.   N       Network

6.   D       Data link

7.   P       Physical

Now we try to understand the layers

1.  A (Application)

We have needed the application to communicate the two or more devices. There are two types of applications, (i): system application (ii): Network applications.

Example of system applications are MS office, Notepad etc.

Example of network applications are MSN Messenger, Yahoo messenger etc

There is no chance that a person work on a note pad and the other person is also working on notepad and they communicate with each other. They have needed the same application not must they needed the network application just like Skype, msn messenger and so on they want to play. So there is one thing to understand that the same kind of applications they needed. So the first layer is application must to communicate between the devices in network and play the main role.

2.   P (Presentation)

Presentation means present to other machine in understand able language. Because machine cannot understand the human language it can understand only machine language. Machine a present the data to machine b in machine language that understands the machine and response it.

3.   S (session)

Session layer is make the session between the machines if the two machines are in working position and running the same kind if application so the session should be complete and the devices or machine are communicate with each other.

Example if a company manager wants to meet the other company manager, he should call to the other manager and fix the appointment and if he doesn’t fix the appointment and go to meet him and on the reaching there he find that he is not in his office so he waste his, so to avoid the wasting time he should call to other manager, it is called session.

4.   T (Transport Layer)

When the application, presentation and session are complete then the transport layer works start. Transport layer put the data form machine “a” to machine “b”.

Data cannot transport form in machine then the machine play its role and make the fragmentation. We type the “hello”  “h” “e” “l” “l” “o” make the pieces and transport.