Physical Layer
Coaxial Cable
Eliminated, too expensive, full of copper
Twisted Pair
Shielded twisted pair (metal insulating layer)
Unshielded twisted pair
Orange white, orange, green, white, green, blue, blue, brown and white, brown standard line sequence
Orange white, orange, green, white, blue, white, green, brown white, brown T568B wire order reversed 46
Green and white, green, orange, white, blue, blue, orange, brown and white, brown T568A line order 1 3,2 6 reversed
Common network cable
Why should the line to be twisted together, prevent the generation of a magnetic field (magnetic field lines will be cut, the opposite current), electrical interference
Class 345,678 twisted pair, the higher the twist the more dense
If the same at both ends of the line, so called direct line (usually T568B)
If not the same at both ends of the line, so called cross-line (T568B end, one end T568A)
Straight lines are generally connected to different devices
Intersecting lines are usually connected to the same kind of device
(In theory, to the contrary, but now the devices are generally adaptive function, will do)
optical fiber
Multimode fiber
A plurality of light beams
Single-mode fiber (more expensive)
Only a beam of light
Total reflection, no scattering