The physical layer provides the upper layer with a way to transmit the original bit stream.

The physical layer provides a physical connection for the upper layer to transmit the original bit stream. The physical layer provides transmission media and interconnection equipment for data communication between devices, and provides a reliable environment for data transmission. In order to give the data link layer the ability to transmit and receive bit streams on a physical transmission medium, the physical layer needs to solve the problems of establishing, maintaining, and releasing physical connections.

The operating environment of this tutorial: Windows 7 system, Dell G3 computer.

The physical layer provides a physical connection for the upper layer to transmit the original bit stream.

Both the server and the client can be understood as a point, and the connection established through lines between points is called a physical connection.

The physical layer (or physical layer, Physical Layer) is the lowest layer in the computer network OSI model. Physical layer specification: Provides mechanical, electronic, functional and normative characteristics for the creation, maintenance, and teardown of physical links required to transmit data. Simply put, the physical layer ensures that raw data can be transmitted over various physical media. Both LAN and WAN belong to layer 1 and 2.

The physical layer is the first layer of OSI. Although it is at the bottom, it is the foundation of the entire open system. The physical layer provides transmission media and interconnection equipment for data communication between devices, and provides a reliable environment for data transmission. If you want to remember this first layer in as few words as possible, it's "Signals and Medium."

Main functions of the physical layer: providing data transmission channels and data transmission for data-end devices.

1. Provide a path for data transmission for data-end devices. The data path can be one physical media or multiple physical media connected. A complete data transfer includes activating the physical connection, transmitting data, and terminating the physical connection. The so-called activation means that no matter how many physical media are involved, the two data terminal devices in communication must be connected to form a path.

2. To transmit data, the physical layer must form an entity suitable for data transmission needs and serve the data transmission. One is to ensure that data can pass through it correctly, and the other is to provide sufficient bandwidth (bandwidth refers to the number of bits (BIT) that can be passed per second) to reduce congestion on the channel. The method of transmitting data can meet the needs of point-to-point, point-to-multipoint, serial or parallel, half-duplex or full-duplex, synchronous or asynchronous transmission.

3. Complete some management work on the physical layer.

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