Transport Layer Working of OSI Model || Networking Chapter IV Part 5 ||

                                           OSI Model - Transport Layer

#Summary - Today we will discuss about working of Transport Layer.

# Transport Layer - This is the fourth layer of OSI Model. This Layer's data unit is known as
 Segment. Transport layer ensures that the entire message reaches in order and handles error control and flow control at the source to destination level. 
Transport Layer receives data from the Session Layer. it divides data into segments and each segment having its own header and passes these segments to the network layer.

At the receiver end, Transport Layer receives packets from the network layer. 

* Responsibilities of Transport Layer -

a) Connection Control - Transport Layer provides either connection-oriented or connection less service. In Connection Oriented service, transport layer establishes a connection with the transport layer at the destination before transmitting segments and terminates the connection when all the data is transferred. In Connection less service, transport layer treats each segment as individual packet and transmit it to the transport layer at destination. 

b) Segmentation and Reassembly - A message is divided into segments with each segment having a sequence number.When the message arrives at the destination, with the help of these sequence number, the transport layer reassembles the message correctly.

c) Port Addressing - Transport Layer includes service-point address (port address) in the header. Using these port addresses transport layer delivers the packets to the correct process.

d) Transport Layer is also performs Error Checking.



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In the next blog we will discuss about Session Layer...