Repeater

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Repeater (RP repeater) works in physical layer Connection device on. It is applicable to the interconnection of two identical networks. Its main function is to extend the distance of network transmission by resending or forwarding data signals. The repeater regenerates and restores the signal network equipment ： OSI Physical layer device of the model.

Repeater is used to extend Network distance Yes, but it belongs to Network interconnection equipment , operating on OSI The repeater has the function of amplifying and regenerating the signals on the line, which is used to expand the LAN Network segment The length of (only used to connect the same LAN segment).

RP repeater is a device for connecting network lines. It is commonly used for two network node between Physical signal The two-way forwarding work of. The repeater mainly completes the functions of the physical layer, which is responsible for transmitting information bit by bit on the physical layer of two nodes, and completing the functions of signal replication, adjustment and amplification to extend the length of the network. Due to the loss, the signal power transmitted on the line will gradually decline, which will cause signal distortion when it decays to a certain extent, so it will lead to reception errors. The repeater is designed to solve this problem. It completes the connection of the physical circuit, amplifies the attenuated signal, and keeps the same as the original data. Generally, the same media is connected at both ends of the repeater, but some repeaters can also transfer different media. Theoretically, the use of repeaters is unlimited, so the network can be extended indefinitely. In fact, this is impossible because Network Standards The delay range of the signal is specified in, and the repeater can only work effectively within the specified range, otherwise it will cause Network failure 。

Chinese name: Repeater
Foreign name: RP REPEATER

Classification: signal communication
Application: Data transmission, data conversion, extended network
Role: Amplified signal and compensated signal attenuation

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Repeater

Repeater (RP repeater) works on OSI Of physical layer , is the center of all nodes on the LAN. Its role is to amplify signals, compensate for signal attenuation, and support long-distance communication. Repeater. It works on the physical layer, only for expansion transmission distance Is transparent to high-level protocols. In fact, the network connected by repeaters is equivalent to a larger network composed of the same wire. The repeater can also connect the networks of different transmission media (10Base 5 and 10Base 2) together, and is used for data link layer The same LAN above is interconnected.^[1]

working principle

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Working principle diagram

The purpose of repeater design is to push your network signals so that they can be transmitted further.

Due to the influence of transmission line noise digital signal or analog signal Only a limited distance can be transmitted. The function of repeater is to regenerate and transmit the received signal, thus increasing the distance of signal transmission. It connects two or more of the same network Network segment 。 as Ethernet Repeaters are often used Expansion bus The maximum length of each section of standard thin cable Ethernet is 185 meters, and there can be 5 sections at most. Therefore, after adding repeaters, the maximum network cable length can be increased to 925 meters. Generally speaking, the network parts at both ends of the repeater are network segments, not Subnet 。

The repeater can connect the cables of the two LANs, re time and regenerate the digital signals on the cables, and then send them out. These functions are OSI model Middle first floor-- physical layer Typical features of. The role of repeaters is to increase the coverage area of the LAN, for example, Ethernet The standard stipulates that the maximum length of a single section of signal transmission cable is 500 meters, but after connecting five sections of cables with repeaters, the maximum length of the signal transmission cable in Ethernet can reach 2500 meters. Some brands of repeaters can connect cable segments of different physical media, such as Coaxial cable And optical cable.

Repeaters only connect Data transmission To another section of cable, regardless of whether there is wrong data or not Network segment Data of.

Advantages and disadvantages

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advantage

The communication distance is expanded.
Added node Maximum number of.
each Network segment Different communication rates can be used.
Improved reliability. When a network failure occurs, it generally affects only individual network segments.
Improved performance.

The main advantages of repeaters are simple installation, convenient use and relatively low price. He not only played Network distance The function of Transmission medium Of network connections in harness. The repeater works in physical layer , completely transparent to high-level protocols.^[2]

shortcoming

Since the repeater regenerates (recovers) the received attenuated signal to the state at the time of transmission and forwards it, the delay is increased.
MAC sublayer of CAN bus does not flow control Function. When the load If it is very heavy, it may be caused by buffer The storage space of is insufficient and overflows, resulting in frame loss.
If the repeater fails Subnet Will have an impact.

quantum repeater

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In 2017, Chinese scientists achieved scalability for the first time quantum repeater Optical demonstration.^[3]

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