Functions of the TCP/IP four-layer model

Functions of the TCP/IP four-layer model

The TCP/IP model is divided into four layers, namely Application layer, Transport layer , Network layer and Host to network layer .

Each layer implements specific functions, provides specific services and access interfaces, and is relatively independent.

1. Host to network layer (first layer)

The function of this layer is to send data from the host to the network, which is equivalent to the Physical layer and data link layer.

2. Network layer

The network layer is the second layer in the TCP/IP model. Initially, it was hoped that when some devices in the network cannot operate normally, network services will not be interrupted and the established network connections can still effectively transmit data; in other words, as long as the source host and target host are in a normal state, the network is required to complete the transmission task. . It is under these demanding design goals that the network layer chose Packer Switching technology as a solution.

Packet switching technology not only allows the packets to be sent to any network to roam independently to the target host, but also ensures that the target host receives the disrupted packets and transmits them to the highest layer for rescheduling. Grouping order. The network layer defines standard packet formats and interface parameters. As long as these standards are met, packets can roam between different networks.

3. Transport layer

The transport layer in the TCP/IP model can not only provide transmission services with different service levels and different reliability guarantees, but also coordinate transmission The difference in transmission speed between the end and the receiving end. Same as OSI transport layer

4 and application layer

. Since not all network services require the functions of the session layer and presentation layer, these functions are gradually integrated into those specific network services of the application layer in the TCP/IP model. The application layer is the application interface of the network operator. Just like the sender puts the letter into the mailbox, the network operator only needs to press the send data button in the application program, and the rest of the tasks are completed by the layers below the application layer.

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