The Transport layer is the core of the OSI model, because it
serves as a bridge between the lower and upper layers to ensure reliable data
transmission. The Transport layer can encounter the following problems:
Unreliable connection between source and destination
Unprotected transmission of data packets
Data transmission delay
Priority of data packets to be transmitted
Problems with error detection and correction
Flooding the slow receiver with data packets
To overcome the above-mentioned problems, the Transport layer uses
the three-way handshake protocol. In this protocol, the source host sends a
connection request to the destination host. If the destination host is ready to
receive data packets, it sends a connection acknowledgment signal to the source
host. After receiving the connection acknowledgment signal from the destination
host, the source host sends the data packet to the destination host.
On receipt of the data packet, the destination host sends an
acknowledgment signal to the source host. If the transmitted data packet is lost
during transmission, the destination host does not send an acknowledgment signal
to the source host.
In such a situation, the source host resends the data packet
after a stipulated period. Using this protocol, the Transport layer provides
retransmission of the lost or corrupted data packets.