OSI's seven-layer model: physical layer, data link layer, network layer, transport layer, session layer, representation layer, application layer.
The physical layer is the underlying network hardware device transmission, and the connection between the two network cards is equal to providing a physical layer. The physical layer describes how the electronic signal is amplified and transmitted, and the like. Standards are: Ethernet and token network
The data link layer is how to transmit frames. The format of the frame transmission and how to transmit the frame is equal to the setting data link layer. Note that on the network, the frame must be universal, otherwise it cannot be transmitted. The frame has Enternet and Token Ring frames.
The network layer function is to translate the address on the network into a corresponding physical address and determine how to send data from the sender to the recipient. Therefore, it can be seen that how to route is implemented by the network layer.
The transport layer is primarily responsible for ensuring data reliability, sequential, and error-free from A to the B point (A, B) may not be on the same network segment). Because if there is no transport layer, the data will not be accepted or explained, so the transport layer is often considered to be the most important layer in the O S I model.
The session layer is established and kept communication between two nodes, commonly used to keep communication between terminals and hosts. The functionality of the session layer includes: establishing a communication and maintaining communication (ie, the smooth communication of the communication), synchronizes the two nodes, determines whether the communication is interrupted and the communication interruption determines where to resend. The session layer is a traffic police in network transmission.
The representation is a translated official between the application layer and the network layer, that is, said that the layer is converted into the data that the application layer is converted into the data that the network layer can understand. (The network layer converts the network address to the physical address, and how to select routing). The encryption and decryption of data is done in the representation layer.
The application layer is to provide an interface to enable the application to use network services, and the application layer usually has a set.
API
Using program calls,
API
It belongs to the application layer.
