OSI MODEL

ADITYA

1BI07EC001

                                                   Hello friends 

                       I share my ppt on Transport Layer of OSI Model. 

 At first , is the slide for T-Layer of OSI Model.

Before I proceed to Transport Layer let me introduce you to OSI Model. 

               What is Open System Interconnection Model?

It illustrates how data communication should take place.

 It devides the process into seven groups called Layers. 

A layer is a collection of conceptually similar functions that provide services to the layer above it and receive services from the layer below it.

 The OSI Model affirms what protocols and standards should be used at each layer.

The lower three layers are called Media Layer because they follow virtual circuit approach. and the upper four layers are called Host layers.

Function of  OSI Layers

1.Physical Layer:- It defines the standards required for physical interconnections e.g.        the Wire. It handles the Bits.

2.Data Link Layer:- It defines the protocols for exchanging data frames over the Network.

3.Network Layer:- It handles routing between networks.

4.Transport Layer:- This layer provide end to end connection between machines. 

                              

5.Session Layer:- This layer provides for dialogue between processes.

6.Presentation Layer:- It provides for translation of data structure between different             architectures.

7.Application Layer:- It provides for application level access to the network, file transfer, remote terminals etc..

By above depiction we understand:

1.During data transmission, the OSI Model follows Top-Down approach i.e. first Application Layer work than Presentation Layer and so on. 

2.When data passes Physical Link, the OSI Model follows Bottom-Up approach i.e. 

first Physical layer work than Data Link Layer and so on. 

                    Depicted above is a business correspondence .

Firstly, the Manager on left writes a Message to be send to other Manager, same work is done by the Application Layer when data is send.

Secondly, the assistant corrects the format, checks errors and prepare final version. which is the work of Presentation layer.

Thirdly, the secretary address and packs the letter which is In OSI done by Session Layer. 

At fourth, the driver drives the letter to the Post Office, which is done by 

Transport Layer in OSI Model.

At fifth, in Post Office a person Intakes the  letter  and sort them according to their compartment. Which is the work of Network Layer of OSI Model.

At sixth, Packaging takes place which in OSI is done by Data Link Layer.

At seventh, the worker loads the letter through a physical medium of transmission i.e.

a truck. In OSI this medium is Physical Layer i.e. a wire. 

Till now the OSI model was following the Top-Down approach but when it is passes through the Physical link it will follow Bottom-Up approach.

Now  when letters reach to other post office :

A worker will take out all the packets which is done by Physical Layer. 

Then the packets are unpacked which is the work of Data Link Layer 

Then the packets are sorted for individual city which is done by Network layer.

Then through Post Man the letter reaches the business corporation which is the work of Transport Layer. 

Then the secretary opens the letter and makes a copy of it which is being done by Session Layer. 

Then the assistant presents the letter to the manager , same is the work of Presentation Layer.

                         Then finally the Manager reads the message.

                     Now , lets go deep in T-Layer (TRANSPORT LAYER)

1.It manages end to end message delivery in a network.

2.It accepts data from the Session Layer breaks it into packets and deliver these packets to the Network layer. 

3.It assures successful arrival of data at the destination device.

4.It checks errors, hence promises that no duplication or errors are there in the data transfer across the network.

5.It affirms, successful data transmission and retransmits the data if any error occur. 

6.Data loss due to poor network management  is handled by using Transport layer.

7.It checks for the packets that are lost or damaged along the way.

                            FUNCTION OF TRANSPORT LAYER          

     

(i) Process Level Addressing:-  

This enables many different software programs to use a network layer protocol simultaneously.

(ii) Multiplexing and De multiplexing:- Using the address, T-Layer protocol multiplex the data received from many application programs for transport, combining them into single stream of data to be sent.

The same protocol receive data and then demultiplex it from the incoming stream of data gram.

(iii) Segmentation,Packaging and reassembly:- The T-Layer segments bulk of data & send over the network into smaller pieces and then reassemble them on the destination device.

(iv) Connection Establishment, Management and Termination:- T-Layer connection oriented protocols are responsible for series of communication required to establish a connection, maintain the data till its requirement, and then terminate the connection.

(v) Acknowledgement and Retransmission:- When data is sent a timer is started ,if the receiver received the data it will sends back an acknowledgement to the transmitter to indicate successful transmission. If no acknowledgement comes back before the timer expires, the data is retransmitted.