Hey there guys,
This video is about
OSI MODEL. In this video we have just explained the basic diagram of OSI MODEL. We will make separate video on each layer. you will get an introduction idea about OSI MODEL means what is OSI MODEL, who and when it was developed, data transfer in OSI MODEL and Basic layout of the layers.
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So, what exactly is OSI Model?.
OSI means Open System Interconnect
In 1974, ISO (International Organization for Standardization) developed a model that was useful in the field of Communication. It is a 7 layer Architecture, A standard set for data transfer with all 7 layers have there own specific task to perform.
7 layers are as follow :-
1. Physical Layer
2. Data Link Layer
3. Network Layer
4. Transport Layer
5. Session Layer
6. Presentation Layer
7. Application Layer
But representation in OSI model is vice versa of this order.
These layers are categorized in 3 classifications depending on there functions. They are as follows :-
1. Upper Layer or Software control Layer
2. Heart of the OSI
3. Lower Layer or Hardware control Layer
1. Upper Layers or Software control Layers :- In this category 3 layers placed Application layer, Presentation layer and Session layer. These layer is responsible for functions to be controlled by software. E.g. - A user is entering https on url of it's computer browser then application layer will place port no 443 header on the data and by the help of encoding the data format will be changed and compressed and all this function is been performed by presentation layer and then session provides time specific for task means to say lease expiry is a good example for this i.e. the function of session layer. So it's clear now that all the function performed by these three layers are been done by the help of software i.e. why it is know as Software control layers.
2. Heart of the OSI :- It is the central layer of the OSI model i.e. Transport layer. It's main function is to identify whether the data will be sent from TCP or UDP.
3. Lower Layers or Hardware control Layers :- These layer is responsible for functions to be controlled by hardware. In this category 3 layers are placed Network layer, Data Link layer and Physical layer. Router works on layer 3 i.e. Network Layer, Switches works on layer 2 i.e. Data Link Layer and the Last is Physical i.e. basically a layer which deals with wires and cables so all the three layers are controlling hardware i.e. why they are known as Hardware control layers.
Now the question comes in mind is why OSI was developed? what was the need???
In late 80's every vendor was using it's own proprietary method for communication so as a result only same vendor devices were able to interact with each other but they were not able to communicate with other vendor devices. To finish that barrier OSI was developed and was accepted by every vendor.
In the above pic the method of data transfer is shown in OSI model, what happens when data is transfer by the sender to receiver.
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Enjoy
Good Luck (Y)
