The transport layer in the network protocol is mainly responsible for data transmission between applications and provides end-to-end services between host application processes. The task of the transport layer is to make optimal use of network resources based on the characteristics of the communication subnet, provide functions for establishing, maintaining, and canceling transmission connections between the session layers of two end systems, and is responsible for end-to-end reliable data transmission.
The operating environment of this tutorial: Windows 7 system, Dell G3 computer.
The transport layer is one of the key layers in the entire network architecture. It is mainly responsible for providing services for communication between processes in two hosts. Since a host runs multiple processes at the same time, the transport layer has multiplexing and demultiplexing capabilities. The transport layer provides transparent data transmission between end users and reliable data transmission services to the upper layer. The transport layer ensures the reliability of data transmission through flow control, segmentation/reassembly, and error control on a given link. Some transport layer protocols are link-oriented, which means that the transport layer can keep track of segments and retransmit failed segments.
The task of the transport layer is to make optimal use of network resources based on the characteristics of the communication subnet, and provide the functions of establishing, maintaining and canceling transmission connections between the session layers of the two end systems. It is responsible for end-to-end Reliable data transmission at the end. At this layer, the protocol data units for information transfer are called segments or messages.
The network layer only transmits the data packets sent by the source node to the destination node according to the network address, while the transport layer is responsible for reliably transmitting the data to the corresponding port. The resource subnet in the computer network is the initiator and receiver of communication, and each device in it is called an endpoint; the communication subnet provides communication services in the network, and the devices in it are called nodes. The following four layers are used for communication control in the OSI reference model, but their control objects are different.
Importance of the transport layer:
The transport layer is the core of the entire protocol hierarchy and the only layer responsible for overall data transmission and control. In the OSI seven-layer model, the transport layer is the highest layer responsible for data communication, and it is also the middle layer between the lower three layers oriented for network communication and the upper three layers oriented for information processing. Because the network layer does not necessarily guarantee service reliability, and users cannot directly control the communication subnet, a layer, the transport layer, is added above the network layer to improve transmission quality.
The transport layer uses the services provided by the network layer and provides communication ports for high-level users to transmit data through the transport layer address, so that the sharing of high-level resources between systems does not have to consider data communication and unreliable data transmission. question. Its main functions are: providing reliable transmission services for an ongoing conversation or connection, realizing the multiplexing of the connection on a single physical connection to the network, and providing end-to-end sequence number, flow control, and error control on a single connection. and recovery services.
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