What is Segmentation and Reassembly of the data
At the seventh layer of the OSI Model that is Application layer the data is passed down and is segmented into the pieces. At the Transport layer there are two types of the segments the first is TCP segment and the other one is UDP segment. A UDP segment called a datagram and a TCP segment called only segment. A UDP header provided source and the destination port and the TCP header provided source and destination port, sequencing, acknowledgment and the flow control. At the destination point when the data is received the whole process is reversed until the data is passed to the application layer.
In TCP each segment header contains a sequence number. This sequence number allow to the transport layer to reassemble the data at the destination point in the same order in which they were transmitted. This process makes sure that the destination application has the data in the exact form the sender intended.
The services using the UDP track the conversation between the applications. They are not concerned with the orders of the data was transmitted or to maintaining the connections. The UDP header does not contain the sequence number, it is a simple design and generates less overhead than TCP.Many applications that use UDP send small amount of the data that can fit in the one segment. There are some applications send large amount of data that split into the multiple segments. The PDU, UDP is referred as a datagram and the terms segment and datagram are sometimes used interchangeably to describe the transport layer PDU.UDP simply reassemble the data in the order that it was forward.
The choice of the transport layer protocol is made by the developer of the application to best meet the user requirement.UDP is a developer preferred transport layer protocol if the application data needs to be deliver across to the network quickly or if the network bandwidth cannot support overhead of control message to exchange between the source and the
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