4-OSI & TCP/IP models

OSI Model:-

This model was created to communicate with between the devices over the network.This model was created bt ISO (International Organization for Standardization  ) . This is the reference model of communication systems over the network.This model has 7 layers . And the traffic from source to 

destination goes on different stages and based on the layers of OSI model , They are taking care of 

of the data based on the stages of OSI model.

And also these are the set of rule to follow to have proper communication over the network.

Here is the below 7 layers of OSI model.

Physical Layer:-
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This layer defines that how to moves the data bits  from one device another.Based on this layer
the cables and connectors are sending the data bits over the network from source to destination .And it converts digital data in to bits format.Essentially this layers puts the data in physical media as bits and receives it in the same way.


Exp-Hub,Cables are working in this layers

Data Link Layer

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This layers encapsulate the data in to frame. And this frame contains of the header and trailer of

source and destination to move on the packet over the network.Most commonly It contains the source and destinations MAC(media Access Control ) inside the frame.

It has two sub layers inside the datalink layer .

MAC(Media Access Control)

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This sub layer is used for to error correction in the frame and for flow control as well.

LLC(Logical Link Control) 

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This sub layer is used for to control the access method.

Example:--Switches function at this layer.

Network Layer

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This layer is responsible to forward the packet based on IP address of the source and destination as well.And this layers count the data as a packet .This layer is using the logical address to forward the packet over the network.There is two types of protocols are used in this layer.

1-Routed protocol--It's forwarding the packet using logical address(Ex-IP,IPX,Novel)

2-Routing Protocol--It's used for finding the path from source to destination.(Ex-RIP,EIGRP,OSPF.etc)

Exp--Routers , firewall are functions at this layers.

Transport Layer

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This layer is going to establish the logical connection between source and destinations used for 

flow control and data recovery.the transport layer is connected with the actual end-to-end transfer

the data of  across the network . Typically the layer 4 examples are TCP(transmission control Protocol) and UDP(User Datagram Protocol). please go through the below examples.

Session layer

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This layer is responsible to create the session between source and destination . And it also

defines that how to terminate the session between two hosts .And also it's going to separate 

the session when the user is trying to accomplish the multiple task at a time  . So the session layer 

is defining some value to each and every session to idintify and also to make separate the session .

    

         It also provides the dialog controls and coordinate communication between the systems.

Presentation Layer

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This layer is responsible for to make compression and encryption to the data.It will take the data from  application layer and translate in to a generic format to forward the data across the network. An example of this is an EBCDIC,ASCII translation .And also this layer present the data to application layer .

Application Layer

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For simplification you can say this layer is closet to user for communication . This layer enables the 

network application to communicate with another network application.below protocols are used in

application layer .