The advantage of coaxial cables is that they can support high bandwidth communication on relatively long repeater free lines, but their disadvantages are also obvious: firstly, they are large in size, and the diameter of thin cables is 3/8 inches thick, occupying a large amount of space in cable ducts; Secondly, it cannot withstand entanglement, pressure, and severe bending, which can damage the cable structure and prevent signal transmission; Finally, there is the high cost, and all of these drawbacks can be overcome by twisted pair. Therefore, in the current LAN environment, it has been basically replaced by the Ethernet physical layer specification based on twisted pair