Transport layer is responsible to make a packets and how data is transmitted in tcp environment. Transport layer recieves data from its upper layer and make packets of data and forward it to the network layer it perform flow control, reliability, sequence number or acknowledgements. Transport layer is a L4 layer of OSI Model which make segmentation..
TCP ( Transmission control protocol)
TCP is a connection oriented protocol. It make packets of your data and provide sequencing and give you acknowledgement of your data and error checking or resend your data until its received to the destination.
UDP (User data gram Protocol)
It is a connectionless protocol which is not provide you acknowledgement . Its only send your data to the destination without any acknowledgment. Voice communication are UDP
