Computer networks can be classified according to the hardware and software technology that is used to interconnect the individual devices in the network, such as optical fibre, Ethernet, Wireless LAN, HomePNA, Power line communication or G.hn.
Ethernet uses physical wiring to connect devices. Frequently deployed devices include hubs, switches, bridges and/or routers. Wireless LAN technology is designed to connect devices without wiring. These devices use radio waves or infrared signals as a transmission medium. ITU-T G.hn technology uses existing home wiring (coaxial cable and power lines) to create a high-speed (up to 1 Gigabit/s) local area network.
Wired technologies
Unshielded Twisted Pair (UTP) Cable
UTP Patch cable
Twisted pair cabling comes in two varieties: shielded and unshielded. Unshielded twisted pair (UTP) is the most popular and is generally the best option for school networks (See figure)
The quality of UTP may vary from telephone-grade wire to extremely high-speed cable. The cable has four pairs of wires inside the jacket. Each pair is twisted with a different number of twists per inch to help eliminate interference from adjacent pairs and other electrical devices. The tighter the twisting, the higher the supported transmission rate and the greater the cost per foot. The EIA/TIA (Electronic Industry Association/Telecommunication Industry Association) has established standards of UTP and rated six categories of wire (additional categories are emerging).
ANSI TIA/EIA 568-B2 - Twisted Pair Categories of Cable Standards
Describes cable standards Level 1 through Cat5e - *** do not confuse this with the 568-B standard, which describes RJ45 wiring pinouts, and colour schemes
In the mid 1980s, companies representing the telecommunications and computer industries were concerned with the lack of a standard for building telecommunications cabling systems. In response to that concern, the Electronic Industries Association (EIA) developed a standard called TIA/EIA-568-A. The higher the standard, the more twists per inch the pairs have, and the better the quality of the jack (RJ-45 typically).
ANSI/EIA (American National Standards Institute/Electronic Industries Association) Standard 568 is one of several standards that specify “categories” (the singular is commonly referred to as “CAT”) of twisted pair cabling systems (wires, junctions, and connectors) in terms of the data rates that they can sustain. The specifications describe the cable material as well as the types of connectors and junction blocks to be used in order to conform to a category. These categories are:
ANSI Category Maximum data rate Usual application
CAT 1 Up to 1 Mbps (1 MHz ) analogue voice (POTS)
Integrated Services Digital Network Basic Rate Interface in ISDN
Doorbell wiring
CAT 2 4 Mbps Mainly used in the IBM Cabling System for Token Ring networks
CAT 3 16 Mbps Voice and data on 10BASE-T Ethernet
CAT 4 20 Mbps Used in 16 Mbps Token Ring
Otherwise not used much
CAT 5 100 Mbps
1000 Mbps (4 pair) 100 Mbps TPDDI
155 Mbps ATM
CAT 5E
(ISO Class D) 100 Mbps TPDDI 155 Mbps ATM
CAT 6
(ISO Class E) Up to 400 MHz Super-fast broadband applications (proposed standard). Used with GigE (1000 Mbps or 1 Gbps)
CAT 7
(ISO Class F) 600-700 MHz Even faster broadband applications (proposed standard)
Note: There is also a standard called 100Base-T4, intended for fast-Ethernet over non-Cat.5 cable. This one uses all four pairs. It is not very common and not supported by nowadays “standard” hardware. HP invented yet another thing called 100Base-VG “AnyLan”, which also uses all four pairs. It’s not very common either.
While longer connections for Gigabit Ethernet use optical fibre, the goal is to leverage the CAT 5 twisted-pair wiring most organizations already have in place for connections out to the desktop. (Four pairs of twisted pair are used.)
include connections to third parties.
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