What is OSI Model

The OSI Model (Open system interconnection model) have 7 layer each layer is responsible for data communication in network. Layer is  a smaller part of communication system. The layer are divided in to part upper layer and lower layer.  The upper layer responsible for user  application how file are represent  on the computer and lower layer responsible for how to communication between network. Each layer receive service from its lower layer.

OSI Model


 7 Layer of OSI Model

Physical Layer

 Physical layer is a lower layer of the OSI model. it is responsible for physical connectivity in the network and establish & terminate the connection in communication medium. It control electrical signal in network . hardware item defined on the physical layer such as – UTP cable, Network adapter, Repeater , hub etc.

Physical Layer Responsible for communication with the data link layer and fragmentation Data into Frames.

Data link Layer

Data Link Layer is the Second layer of the OSI Model which is responsible for the Communication with the Network layer which is above it and the Communication with the Physical Layer. Its also responsible to encode the bit into packet and decode the packet into bit. Its provide error free transfer the frame one node to another node. 
Its Responsible for the transmitting and receiving frames within the Local area Network and Establish and termination link between two nodes.

Functions of the Data Link Layer

  • Logical Link Control. 
  • Media Access Control.
  • Data Framing.
  • Hardware Addressing.
  • Error detection and Handling.


Network Layer

Network layer is the Third Layer of the OSI Model which is responsible for the Communication with the Transport layer and Data link Layer and Responsible for the Connectivity between host and network. Network Layer work based on the IP Address which is called Logical Address . Its use to route the packet among the inter-networks. Its responsible for the provide Connectivity between two or more then two different network.

Function of the Network Layer
  • Routing.
  • Logical Addressing ( IP Addressing).
  • Datagram Encapsulation.
  • Fragmentation and Reassembling .
  • Error handling and diagnostics.
Network Layer Protocols -: Internet Protocol , ICMP and IPX/SPX.

Transport layer

Transport layer is the 4th layer of the OSI Model. Its responsible for the deliver transfer packet  error -free and sequence. Its also Responsible for the recover packet from error and Lose. Its use to communicate with the Session Layer and Transport layer. Transport layer responsible for the Reliable Communication.
Its receive the message from the Session layer and then Split the message into smaller unit and then Transfer smaller unit to the Network Layer. Smaller unit called segment.
Transport layer protocol 
  1. Transmission control protocol (TCP).
  2. User Datagram protocol (UDP).

Session Layer

Session layer is the 5th layer of the OSI Model responsible for the Create session establishment, maintenance and termination. It provide the connection between two host and also provide connection to the remote machine. 
Its also responsible for the Communicate with the Presentation layer and transport Layer.
Transport layer Protocol -: FTP and Telnet.


Presentation layer

Presentation layer is the sixth layer of the OSI Model. Its responsible for the how data to be present on the Local machine. Its provide the Suitable format to be  the understandable on the Local machine because of network there is the many operating system such as – Windows, Mac OS , Linux etc.  Its also provide encryption and Compression of the Data.
Functions of the Presentation Layer
  • Translation.
  • Encryption.
  • Compression.


Application Layer

Application layer is the 7th layer of the OSI Model which is Responsible for the show the data to the User. Its provide the user interface . Its also provide to communication to the Presentation layer. Its provide the interface between Application and user.
Functions of the Application Layer
  • File Sharing and resources.
  • Remote Files and printer access.
  • Web Browsers .
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Rakesh Kumar
Rakesh Kumar is a Network engineer and a Blogger. He is crazy for learn and write about Technology , Tech and Computer Tips and Tricks Blog.