HTTP from entry to the ground (1)--five-layer network model

Introduction to five-tier network model

The realization of the Internet relies on the network protocol. The network protocol is divided into several layers, there are a lot of controversy about how to layer, compared with five-layer model, seven-layer model, four-layer model. Today, let's talk about the five-tier network model.

As can be seen from the name, the five-tier network model divides the network protocol into five tiers, each of which has corresponding network protocols. From top to bottom, respectively:

• Application Layer
• Transport Layer
• Network layer
• Data Link Layer
• Physical Layer

Physical Layer

The primary function of the physical layer is to define how the physical device transmits data.

Data Link Layer

The Data link layer establishes data link links between the entities that communicate.

Network layer

The network layer creates a logical link for the transfer of data between nodes.

The bottom of the three layer is relatively low-level, if only to do Web applications, it can be said that the basic and the three layers of no contact; but the top two layers are closely related to web development.

Transport Layer

The transport layer provides the user with reliable end-to-end (end-to-end) services, such as client-to-server services.

The transport layer shields the details of the underlying data communication from the upper layers, as the upper application does not need to focus on the underlying implementation details, which reduces the amount of data and improves security.

The transport layer has two protocols: the TCP protocol and the UDP protocol.

Application Layer

The application layer provides many services for the application software, because the application layer is built on the TCP protocol, so no matter how the application layer data transmission is based on the TCP protocol.

As with the reason for the transport layer, the application layer also shields the details of the network transmission.

The most important protocol for the application layer is the familiar HTTP protocol.

HTTP from entry to the ground (1)--five-layer network model