Section 10

• The OSI Layer 1 conveys the bit stream, electrical impulse, light, radio, etc, through the network at the electrical and mechanical level.
• It provides the hardware menas of sending and receiving data.

• Ethernet LAN connections can be carried over coaxial cable, twisted copper pair cable, fiber cable or wireless.
• It’s commonly used the copper UTP (unshielded twisted pair) to connect to switches, which a connector type RJ-45.

• The receive and transmit wires in a UTP cable can be wired to the RJ-45 connector as either straight-trough or crossover.
• Straight-through cables are used to connect an end device like a router or PC.
• Crossover cables are used to connect devices together directly, like to devices of the same type.
• Modern switches support Auto MDI-X, where the receive and transmit signals are reconfigured automatically to yield the expected result.

• Fiber optic cables can be used to support longer distances or higher bandwidth requirements.
• For example, between separate buildings in a campus, or for switch to switch connections inside a building.

The fiber can be single mode or multi-mode, where single mode supports higher bandwidth and longer distances, but is more expensive.

Also, fiber connectors are very different.

This allows to give power to certain stuff like repeaters, Raspberry Pi, etc. This can be achieved by PoE switches or a Power Injector.