‫So now we're in the fourth layer of the OCI reference model, the transport layer.
‫Welcome to the layer of TCP.
‫The transport layer is a level at which system reliability and quality are ensured.
‫The basic function of the transport layer is to accept data from the layer above.
‫Split it up into smaller units.
‫Pass these data units to the network layer.
‫And ensure that all the pieces arrive correctly at the other end.
‫OK, so now let's look at the functions of the transport layer in detail.
‫Service point addressing.
‫Transport layer header includes service point address, which is the port address, this layer gets
‫the message to the correct process on the computer, unlike network layer, which gets each packet to
‫the correct computer.
‫Segmentation and reassembling.
‫A message is divided into segments.
‫Now, each segment contains a sequence number, which enables this layer to reassemble the message.
‫The message is reassembled correctly upon arrival at the destination and replaces packets which were
‫lost in transmission.
‫Connection control.
‫It includes two types connection list transport layer.
‫Each segment is considered as an independent packet and delivered to the transport layer at the destination
‫machine.
‫Connection oriented transport layer.
‫Before delivering packets, connection is made with the transport layer at the destination machine.
‫Flow control.
‫And this layer flow control is performed end to end.
‫The rate of data transmission between two nodes must sometimes be managed to prevent a fast sender from
‫transmitting more data than can be supported by the receiving data buffer, causing a buffer overrun.
‫And we don't want that.
‫Error control, error control is performed end to end in this layer to ensure that the complete message
‫arrives at the receiving transport layer without any error.
‫Error correction is done through retransmission.
‫On the Internet, TCP and UDP provide the services for most applications.
‫Coming up next, we'll look at all the other details of the transport layer under TCP and UDP topics.