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OSI Model

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Manupuri Nithin
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The OSI (Open Systems Interconnection) model provides a framework for understanding how communication occurs between different systems in computer networks. Osi model has a set of layers and it responsibilities in a computer network and it divides into the 7 layers.

  1. Application Layer

2. Presentation Layer.

  1. Session Layer

4. Transport Layer

5. Network layer

  1. Data Link Layer

  2. Physical Layer

1.Application Layer: It is a application user interface where user can interact with the application.it lies in the browser. and it has a set of protocols that are HTTP, FTP, TELNET, DNS etc.. It will give data to the presentation layer.

Http: it used for web request and it is a application Layer protocol

Ftp: It is file transfer protocol it is used to transfer files

2.Presentation Layer: It receives the data from application layer it converts the data into the machine language i.e (from ASCII to EBCDIC(Extended Binary Coded Decimal Inter change code).It provides abstraction, and this presentation Layer will assume that data will send to downwards then it will TakeCare of it, Data in here also compresses, this data can be Lossy, Lossely.

here SSL will be used.

Session Layer:

This Session Layer protocol helps in managing the connections it enables the sending and receiving data. Before Session is establish it calls Authentication

Transport Layer:

It tells us how data will transfer which protocol will used to transfer data, we have TCP, UDP protocols to transfer data.

First data will be received from the Session Layer this data will divided into small units called segment.

every segment contains Port number, sequence number and flow control and Error control.

sequence number-> reassembles the data in the correct order.

Flow control-> Transport Layer will control the amount of data will be transferred.

Error control-> it checks the correctness of data, if some data packets lost or corrupted it add's checksum to check whether the data is correct or not.

Connection Oriented transmission -> TCP (it provides the feedback)

Connectionless oriented transmission ->UDP (It is faster than TCP because it doesn't provide any feedback)

Network Layer:

It works for transmission of received data segments from one computer to another that is located in different network or same network (Router lives here)

Functionality of Network Layer:

Logical addressing will be done here (i.e ip addressing).

Network layer will assign the sender & receiver Ip address to every segments, in Network layer we call packets(segments).

Routing takes place in Network Layer.

DataLink Layer:

This layer receives data packets from the network layer and this packets contains the ip address of sender and receiver and subnet.

This layer will assign mac address to the data packets, here In this layer we call Packet as a Frames.

Media Access Control-> It is a 12-digit alphanumeric number of the network Interface of the Computer (It uses MAC addresses to uniquely identify devices within a local network.)

This data link layer performs two functions it allows all the upper layers of the osi model & access these frames.

Physical Layer:

It is responsible for transmitting raw binary data (0s and 1s) over the physical medium. It deals with the hardware components.It gets data in bits from above layer and it converts this bits into electrical signals, radio signals .

and At the reviver section physical layer will receives this signals and converts these signals into bits and passes through the datalink layer as a frame

OSI