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‫So now we're in the fourth layer of the OCI reference model, the transport layer.

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‫Welcome to the layer of TCP.

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‫The transport layer is a level at which system reliability and quality are ensured.

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‫The basic function of the transport layer is to accept data from the layer above.

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‫Split it up into smaller units.

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‫Pass these data units to the network layer.

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‫And ensure that all the pieces arrive correctly at the other end.

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‫OK, so now let's look at the functions of the transport layer in detail.

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‫Service point addressing.

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‫Transport layer header includes service point address, which is the port address, this layer gets

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‫the message to the correct process on the computer, unlike network layer, which gets each packet to

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‫the correct computer.

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‫Segmentation and reassembling.

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‫A message is divided into segments.

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‫Now, each segment contains a sequence number, which enables this layer to reassemble the message.

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‫The message is reassembled correctly upon arrival at the destination and replaces packets which were

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‫lost in transmission.

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‫Connection control.

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‫It includes two types connection list transport layer.

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‫Each segment is considered as an independent packet and delivered to the transport layer at the destination

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‫machine.

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‫Connection oriented transport layer.

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‫Before delivering packets, connection is made with the transport layer at the destination machine.

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‫Flow control.

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‫And this layer flow control is performed end to end.

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‫The rate of data transmission between two nodes must sometimes be managed to prevent a fast sender from

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‫transmitting more data than can be supported by the receiving data buffer, causing a buffer overrun.

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‫And we don't want that.

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‫Error control, error control is performed end to end in this layer to ensure that the complete message

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‫arrives at the receiving transport layer without any error.

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‫Error correction is done through retransmission.

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‫On the Internet, TCP and UDP provide the services for most applications.

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‫Coming up next, we'll look at all the other details of the transport layer under TCP and UDP topics.