7.3 Physical Media - Connecting Communication

	Physical media are used to transfer data between network devices.
	They can be guided, which use a medium guide to transfer data or unguided which are the wireless media.
	Guided media include Unshielded Twisted Pair (UTP), Shielded Twisted Pair (STP), coaxial cables, and fiber cables (fiber-optics).
	UTP and STP are made of copper, they consist of a set of wires with each one insulated and twisted with another wire to make a twisted pair (normally there are 4 pairs of wires).
	UTP and STP are made of copper, they consist of a set of wires with each one insulated and twisted with another wire to make a twisted pair (normally there are 4 pairs of wires).
	STP has superior performance compared with UDP because it shields the pairs to increase the reduction in electromagnetic interference.
	The shielding in STP can be for each twisted pair, it can also be for the group of twisted pairs. Additionally, both techniques can be used in the same cable.
	There are two kinds of coaxial cables thicknet and thinnet, they differ in their diameters, bandwidth, and the distance that each can run.
	There are two kinds of coaxial cables thicknet and thinnet, they differ in their diameters, bandwidth, and the distance that each can run.
	Fiber-optics use light instead of electromagnetic signals to transfer data, hence, they are reluctant to electromagnetic noise.

7.3 Physical Media - Connecting Communication

	However, fiber cables are expensive, fragile, and difficult to be installed.
	There are two kinds of fiber-optics; single-mode and multimode fiber-optics.
	Single-mode fiber has a smaller core diameter compared with multimode and it is used as a wave guide to transfer data with larger data rates compared with multi-mode.
	Multi-mode fiber cables allows light to go in several paths, and hence it has smaller data transfer rates compared with single-mode.
	Multi-mode fiber cables allows light to go in several paths, and hence it has smaller data transfer rates compared with single-mode.
	There are several standards for the wireless media such as:

		IEEE 802.11, which provides the specifications of the Wireless LAN (WLAN).
		IEEE 802.15, which provides the specifications of the Bluetooth used in Wireless Personal Area Network (WPAN).
		IEEE 802.16, which provides the specifications of the WiMAX networks.

IEEE 802.11 provides several specifications for the WLAN, that includes:

7.3 Physical Media - Connecting Communication

		802.11a: Provides up to 54Mbps transmission in the 5GHz band.
		802.11b: Provides up to 11Mbps transmission in the 2.4GHz band.
		802.11g: Provides up to 54Mbps transmission in the 2.4GHz band.
		802.11n: Provides a data rate from 54Mbps to 600Mbps, and operates on both the 2.4GHz and 5GHz bands.

	802.11a is not compatible with 802.11b/g.
	The guided media should have proper connectors and the following are the connectors that are used with guided media:

		RJ-45 is used as a connector for STP and UTP media.
		BNC is used as a connector for coaxial cables.
		ST, SC, and LC are the connectors that are used with fiber cables.