What is the data transmission unit of the transport layer?

The data transmission unit of the transport layer is: data segment. The transport layer is the fourth layer of the "ISO OSI" protocol, which implements end-to-end data transmission; this layer is the first end-to-end layer when two computers communicate through the network, and has a buffering effect.

The data transmission unit of the transport layer is: data segment.

The unit is:

1. The PDU of the application layer is called data;

2. The PDU of the transport layer is called data segment. ;

3. The PDU of the network layer is called a data packet;

4. The PDU of the network interface layer is called a frame;

5. The PDU actually used for the actual transmission of the medium Called bits (bits).

Transport layer: It is the fourth layer protocol of the ISO OSI protocol and realizes end-to-end data transmission.

This layer is the first end-to-end layer when two computers communicate data through the network, and has a buffering effect.

When the network layer service quality cannot meet the requirements, it will improve the service to meet the high-level requirements; when the network layer service quality is better, it only uses very little work.

The transport layer can also be reused, that is, multiple logical connections are created on one network connection.

The transport layer provides transparent data transmission between end users and provides reliable data transmission services to the upper layer.

The transport layer implements flow control, segmentation/reassembly, and error control on a given link. Some protocols are link-oriented.

This means that the transport layer can keep track of segments and retransmit failed segments.

Basic functions

1. Split and reorganize data;

2. Addressing by port number;

3.Connect Management;

4. Error control, flow control, and error correction functions;

5. The transport layer should provide the reliability of communication services to the session layer to avoid message errors, loss, Delay time disorder, duplication, disorder and other errors.

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