Transmission concepts in layer-7 network protocols

We all know that network protocol traffic is inseparable from its hierarchical structure. In the layer-7 network protocol model, the transport layer between the application layer and the network layer is the center of gravity of the layered network architecture. its important task is to directly provide communication services to applications running on different hosts.

The Transport Layer Protocol provides logical communication for application processes on different hosts. logical communication means that even though the application processes of communication are not physically connected (in fact, they may be in different locations of a planet, through a variety of routers and various connection types), and from the application perspective, they are like physical connections. applications use the logical communication provided by the transport layer to transmit information to each other without considering the physical infrastructure used to transmit the information. group. 1. describes the concept of logical communication.

As shown in figure 1, the transport layer protocol is implemented on the terminal system, instead of on the network router. The network router only acts on the network layer field of 3-PDU, not the transport layer field.

Figure 1 layer-7 network protocol model transport layer provides logical rather than physical communication between two applications

At the sender, the transport layer converts messages sent by applications into 4-PDU (transport layer protocol data units ). the process of constructing 4-PDU is to divide the application message into smaller blocks and add a header to each block. the Transport Layer then passes these 4-PDU to the network layer. at the network layer, every 4-PDU is encapsulated into a 3-PDU. at the receiver, the transport layer receives 4-PDU transmitted from the network layer, removes the headers of these 4-PDU, reassembles the messages, and finally delivers them to the receiving process.

A computer network can develop multiple transport layer protocols for network applications. for example, the Internet has two Protocols: TCP and UDP. each Protocol provides a set of different services for calling applications.

All transport layer protocols provide multiplexing and multiplexing services for applications. in addition to multiplexing, the transport layer protocol also provides other services for application processes, including reliable data transmission, bandwidth assurance, and transmission latency assurance.

I believe you have some knowledge about some transmission concepts in the layer-7 network protocol model. In the future, we will add some content in this article.