Net+ Chapter 3

Front 1

1 gigabit per second (Gbps)

Back 1

1,000,000,000 bits per second.

Front 2

1 kilobit per second (Kbps)

Back 2

1000 bits per second.

Front 3

1 megabit per second (Mbps)

Back 3

1,000,000 bits per second.

Front 4

1 terabit per second (Tbps)

Back 4

1,000,000,000,000 bits per second.

Front 5

100-pair wire

Back 5

UTP supplied by a telecommunications carrier that contains 100 wire pairs.

Front 6

110 block

Back 6

Part of an organization’s cross-connect facilities, a type of punch-down block designed to terminate Cat 5 or better twisted pair wires.

Front 7

25-pair wire

Back 7

UTP supplied by a telecommunications carrier that contains 25 wire pairs.

Front 8

alien cross talk

Back 8

EMI interference induced on one cable by signals traveling over a nearby cable.

Front 9

AM (amplitude modulation)

Back 9

A modulation technique in which the amplitude of the carrier signal is modified by the application of a data signal.

Front 10

amplifier

Back 10

A device that boosts, or strengthens, an analog signal.

Front 11

amplitude

Back 11

A measure of a signal’s strength.

Front 12

analog

Back 12

A signal that uses variable voltage to create continuous waves, resulting in an

inexact transmission.

Front 13

attenuation

Back 13

The extent to which a signal has weakened after traveling a given distance.

Front 14

AWG (American Wire Gauge)

Back 14

A standard rating that indicates the diameter of a wire, such as the conducting core of a coaxial cable.

Front 15

bandwidth

Back 15

A measure of the difference between the highest and lowest frequencies that a

medium can transmit.

Front 16

baseband

Back 16

A form of transmission in which digital signals are sent through direct current

pulses applied to a wire. This direct current requires exclusive use of the wire’s capacity, so

baseband systems can transmit only one signal, or one channel, at a time. Every device on a

baseband system shares a single channel.

Front 17

bend radius

Back 17

The radius of the maximum arc into which you can loop a cable before you will cause data transmission errors. Generally, a twisted pair cable’s bend radius is equal to or greater than four times the diameter of the cable.

Front 18

binary

Back 18

A system founded on using 1s and 0s to encode information.

Front 19

bit (binary digit)

Back 19

A bit equals a single pulse in the digital encoding system. It may have only one of two values: 0 or 1.

Front 20

BNC (Bayonet Neill-Concelman, or British Naval Connector)

Back 20

A standard for coaxial cable connectors named after its coupling method and its inventors.

Front 21

BNC connector

Back 21

A coaxial cable connector type that uses a twist-and-lock (or bayonet)

style of coupling. It may be used with several coaxial cable types, including RG-6 and

RG-59.

Front 22

braiding

Back 22

A braided metal shielding used to insulate some types of coaxial cable.

Front 23

broadband

Back 23

A form of transmission in which signals are modulated as radio frequency analog pulses with different frequency ranges. Unlike baseband, broadband technology does not involve binary encoding. The use of multiple frequencies enables a broadband system to operate over several channels and, therefore, carry much more data than a baseband system.

Front 24

broadcast

Back 24

A transmission that involves one transmitter and multiple, undefined receivers.

Front 25

byte

Back 25

Eight bits of information. In a digital signaling system, broadly speaking, 1 byte

carries one piece of information.

Front 26

cable plant

Back 26

The hardware that constitutes the enterprise-wide cabling system.

Front 27

Cat

Back 27

Abbreviation for the word category when describing a type of twisted pair cable. For

example, Category 5 unshielded twisted pair cable may also be called Cat 5.

Front 28

Cat 3 (Category 3)

Back 28

A form of UTP that contains four wire pairs and can carry up to 10 Mbps, with a possible bandwidth of 16 MHz. Cat 3 was used for 10-Mbps Ethernet or 4-Mbps token ring networks

Front 29

Cat 5 (Category 5)

Back 29

A form of UTP that contains four wire pairs and supports up to 100-Mbps throughput and a 100-MHz signal rate.

Front 30

Cat 5e (Enhanced Category 5)

Back 30

A higher-grade version of Cat 5 wiring that contains highquality

copper, offers a high twist ratio, and uses advanced methods for reducing cross talk.

Enhanced Cat 5 can support a signaling rate of up to 350 MHz, more than triple the

capability of regular Cat 5.

Front 31

Cat 6 (Category 6)

Back 31

A twisted pair cable that contains four wire pairs, each wrapped in foil insulation. Additional foil insulation covers the bundle of wire pairs, and a fire-resistant plastic sheath covers the second foil layer. The foil insulation provides excellent resistance to cross talk and enables Cat 6 to support a signaling rate of 250 MHz and at least six times the throughput supported by regular Cat 5.

Front 32

Cat 6a (Augmented Category 6)

Back 32

A higher-grade version of Cat 6 wiring that further reduces attenuation and cross talk and allows for potentially exceeding traditional network segment length limits. Cat 6a is capable of a 500-MHz signaling rate and can reliably transmit data at multi-gigabit per second rates.

Front 33

Cat 7 (Category 7)

Back 33

A twisted pair cable that contains multiple wire pairs, each separately shielded then surrounded by another layer of shielding within the jacket. Cat 7 can support up to a 1-GHz signal rate. But because of its extra layers, it is less flexible than other forms of twisted pair wiring.

Front 34

channel

Back 34

A distinct communication path between two or more nodes, much like a lane is a

distinct transportation path on a freeway. Channels may be separated either logically (as in

multiplexing) or physically (as when they are carried by separate wires).

Front 35

cladding

Back 35

The glass or plastic shield around the core of a fiber-optic cable. Cladding reflects light back to the core in patterns that vary depending on the transmission mode. This reflection allows fiber to bend around corners without impairing the light-based signal.

Front 36

coaxial cable

Back 36

A type of cable that consists of a central metal conducting core, which might be solid or stranded and is often made of copper, surrounded by an insulator, a braided metal shielding, called braiding, and an outer cover, called the sheath or jacket. Coaxial cable, called “coax” for short, was the foundation for Ethernet networks in the 1980s. Today it’s used to connect cable Internet and cable TV systems.

Front 37

conduit

Back 37

The pipeline used to contain and protect cabling. Conduit is usually made from metal.

Front 38

connectors

Back 38

The pieces of hardware that connect the wire to the network device, be it a file server, workstation, switch, or printer.

Front 39

core

Back 39

The central component of a cable designed to carry a signal. The core of a fiber-optic cable, for example, consists of one or several glass or plastic fibers. The core of a coaxial copper cable consists of one large or several small strands of copper.

Front 40

crossover cable

Back 40

A twisted pair patch cable in which the termination locations of the transmit and receive wires on one end of the cable are reversed.

Front 41

cross talk

Back 41

A type of interference caused by signals traveling on nearby wire pairs infringing on another pair’s signal.

Front 42

DB-9 connector

Back 42

A type of connector with nine pins that’s commonly used in serial communication that conforms to the RS-232 standard.

Front 43

DB-25 connector

Back 43

A type of connector with 25 pins that’s commonly used in serial communication that conforms to the RS-232 standard.

Front 44

demarcation point (demarc)

Back 44

The point of division between a telecommunications service carrier’s network and a building’s internal network.

Front 45

demultiplexer (demux)

Back 45

A device that separates multiplexed signals once they are received and regenerates them in their original form.

Front 46

digital

Back 46

As opposed to analog signals, digital signals are composed of pulses that can have a

value of only 1 or 0.

Front 47

DWDM (dense wavelength division multiplexing)

Back 47

A multiplexing technique used over single-mode or multimode fiber-optic cable in which each signal is assigned a different wavelength for its carrier wave. In DWDM, little space exists between carrier waves in order to achieve extraordinary high capacity.

Front 48

EMI (electromagnetic interference)

Back 48

A type of interference that may be caused by motors, power lines, televisions, copiers, fluorescent lights, or other sources of electrical activity

Front 49

entrance facilities

Back 49

The facilities necessary for a service provider (whether it is a local phone company, Internet service provider, or long-distance carrier) to connect with another organization’s LAN or WAN.

Front 50

FDM (frequency division multiplexing)

Back 50

A type of multiplexing that assigns a unique

frequency band to each communications subchannel. Signals are modulated with different

carrier frequencies, then multiplexed to simultaneously travel over a single channel.

Front 51

ferrule

Back 51

A short tube within a fiber-optic cable connector that encircles the fiber strand and

keeps it properly aligned.

Front 52

fiber-optic cable

Back 52

A form of cable that contains one or several glass or plastic fibers in its core. Data is transmitted via pulsing light sent from a laser or light-emitting diode (LED) through the central fiber (or fibers). Fiber-optic cables offer significantly higher throughput than copper-based cables. They may be single-mode or multimode and typically use wavedivision

multiplexing to carry multiple signals.

Front 53

FM (frequency modulation)

Back 53

A method of data modulation in which the frequency of the carrier signal is modified by the application of the data signal.

Front 54

frequency

Back 54

The number of times that a signal’s amplitude changes over a fixed period of time, expressed in cycles per second, or hertz (Hz).

Front 55

F-Type connector

Back 55

A connector used to terminate coaxial cable used for transmitting television and broadband cable signals.

Front 56

full-duplex

Back 56

A type of transmission in which signals may travel in both directions over a medium simultaneously. May also be called, simply, “duplex.”

Front 57

half-duplex

Back 57

A type of transmission in which signals may travel in both directions over a medium, but in only one direction at a time.

Front 58

hertz (Hz)

Back 58

A measure of frequency equivalent to the number of amplitude cycles per second.

Front 59

IDF (intermediate distribution frame)

Back 59

A junction point between the MDF and concentrations of fewer connections—for example, those that terminate in a telecommunications closet.

Front 60

impedance

Back 60

The resistance that contributes to controlling an electrical signal. Impedance is

measured in ohms.

Front 61

latency

Back 61

The delay between the transmission of a signal and its receipt.

Front 62

LC (local connector)

Back 62

A connector used with single-mode or multimode fiber-optic cable.

Front 63

MDF (main distribution frame)

Back 63

Also known as the main cross-connect, the first point of interconnection between an organization’s LAN or WAN and a service provider’s facility.

Front 64

media converter

Back 64

A device that enables networks or segments using different media to interconnect and exchange signals.

Front 65

modem

Back 65

A device that modulates analog signals into digital signals at the transmitting end for transmission over telephone lines, and demodulates digital signals into analog signals at

the receiving end.

Front 66

modulation

Back 66

A technique for formatting signals in which one property of a simple carrier wave is modified by the addition of a data signal during transmission.

Front 67

MT-RJ (mechanical transfer registered jack)

Back 67

A connector used with single-mode or multimode fiber-optic cable.

Front 68

multiplexer

Back 68

A device that separates a medium into multiple channels and issues signals to each of those subchannels.

Front 69

multiplexing

Back 69

A form of transmission that allows multiple signals to travel simultaneously over one medium.

Front 70

NEXT (near end cross talk)

Back 70

Cross talk, or the impingement of the signal carried by one wire onto a nearby wire, that occurs between wire pairs near the source of a signal.

Front 71

noise

Back 71

The unwanted signals, or interference, from sources near network cabling, such as electrical motors, power lines, and radar.

Front 72

nonbroadcast point-to-multipoint transmission

Back 72

A communications arrangement in which a single transmitter issues signals to multiple, defined recipients.

Front 73

optical loss

Back 73

The degradation of a light signal on a fiber-optic network.

Front 74

overhead

Back 74

The nondata information that must accompany data for a signal to be properly routed and interpreted by the network.

Front 75

patch cable

Back 75

A relatively short section (usually between 3 and 25 feet) of cabling with connectors on both ends.

Front 76

patch panel

Back 76

A wall-mounted panel of data receptors into which cross-connect patch cables from the punch-down block are inserted.

Front 77

phase

Back 77

A point or stage in a wave’s progress over time.

Front 78

plenum

Back 78

The area above the ceiling tile or below the subfloor in a building.

Front 79

point-to-multipoint

Back 79

A communications arrangement in which one transmitter issues signals to multiple receivers. The receivers may be undefined, as in a broadcast transmission, or defined, as in a nonbroadcast transmission.

Front 80

point-to-point

Back 80

A data transmission that involves one transmitter and one receiver.

Front 81

populated segment

Back 81

A network segment that contains end nodes, such as workstations.

Front 82

punch-down block

Back 82

A panel of data receptors into which twisted pair wire is inserted, or punched down, to complete a circuit.

Front 83

regeneration

Back 83

The process of retransmitting a digital signal. Regeneration, unlike amplification, repeats the pure signal, with none of the noise it has accumulated.

Front 84

repeater

Back 84

A device used to regenerate a signal.

Front 85

RFI (radio frequency interference)

Back 85

A kind of interference that may be generated by

broadcast signals from radio or TV antennas.

Front 86

RG-6

Back 86

A type of coaxial cable with an impedance of 75 ohms and that contains an 18 AWG core conductor. RG-6 is used for television, satellite, and broadband cable connections.

Front 87

RG-8

Back 87

A type of coaxial cable characterized by a 50-ohm impedance and a 10 AWG core. RG-8 provided the medium for the first Ethernet networks, which followed the now obsolete 10BASE-5 standard.

Front 88

RG-58

Back 88

A type of coaxial cable characterized by a 50-ohm impedance and a 24 AWG core.

RG-58 was a popular medium for Ethernet LANs in the 1980s, used for the now-obsolete

10BASE-2 standard.

Front 89

RG-59

Back 89

A type of coaxial cable characterized by a 75-ohm impedance and a 20 or 22 AWG core, usually made of braided copper. Less expensive but suffering greater attenuation than the more common RG-6 coax, RG-59 is used for relatively short connections.

Front 90

RJ-11 (registered jack 11)

Back 90

The standard connector used with unshielded twisted pair cabling (usually Cat 3 or Level 1) to connect analog telephones.

Front 91

RJ-45 (registered jack 45)

Back 91

The standard connector used with shielded twisted pair and unshielded twisted pair cabling.

Front 92

RS-232 (Recommended Standard 232)

Back 92

A Physical layer standard for serial communications, as defined by EIA/TIA.

Front 93

RTT (round-trip time)

Back 93

The length of time it takes for a packet to go from sender to receiver, then back from receiver to sender. RTT is usually measured in milliseconds.

Front 94

SC (subscriber connector or standard connector)

Back 94

A connector used with single-mode or

multimode fiber-optic cable.

Front 95

serial

Back 95

A style of data transmission in which the pulses that represent bits follow one another along a single transmission line. In other words, they are issued sequentially, not simultaneously.

Front 96

serial cable

Back 96

A cable, such as an RS-232 type, that permits serial data transmission.

Front 97

sheath

Back 97

The outer cover, or jacket, of a cable.

Front 98

simplex

Back 98

A type of transmission in which signals may travel in only one direction over a medium.

Front 99

SMF (single-mode fiber)

Back 99

A type of fiber-optic cable with a narrow core that carries light pulses along a single path data from one end of the cable to the other end. Data can be transmitted faster and for longer distances on single-mode fiber than on multimode fiber. However, single-mode fiber is more expensive.

Front 100

ST (straight tip)

Back 100

A connector used with single-mode or multimode fiber-optic cable.

Front 101

statistical multiplexing

Back 101

A method of multiplexing in which each node on a network is assigned a separate time slot for transmission, based on the node’s priority and need.

Front 102

STP (shielded twisted pair)

Back 102

A type of cable containing twisted-wire pairs that are not only individually insulated, but also surrounded by a shielding made of a metallic substance such as foil.

Front 103

straight-through cable

Back 103

A twisted pair patch cable in which the wire terminations in both connectors follow the same scheme.

Front 104

structured cabling

Back 104

A method for uniform, enterprise-wide, multivendor cabling systems specified by the TIA/EIA 568 Commercial Building Wiring Standard. Structured cabling is based on a hierarchical design using a high-speed backbone.

Front 105

subchannel

Back 105

One of many distinct communication paths established when a channel is multiplexed or modulated.

Front 106

TDM (time division multiplexing)

Back 106

A method of multiplexing that assigns a time slot in the flow of communications to every node on the network and, in that time slot, carries data from that node.

Front 107

telecommunications closet

Back 107

Also known as a “telco room,” the space that contains connectivity for groups of workstations in a defined area, plus cross-connections to IDFs or, in smaller organizations, an MDF. Large organizations may have several telecommunications closets per floor, but the TIA/EIA standard specifies at least one per floor.

Front 108

3

Thicknet

Back 108

An IEEE Physical layer standard for achieving a maximum of 10-Mbps throughput over coaxial copper cable. Thicknet is also known as 10Base-5. Its maximum segment length is 500 meters, and it relies on a bus topology.

Front 109

Thinnet

Back 109

An IEEE Physical layer standard for achieving 10-Mbps throughput over coaxial copper cable. Thinnet is also known as 10Base-2. Its maximum segment length is 185 meters, and it relies on a bus topology.

Front 110

throughput

Back 110

The amount of data that a medium can transmit during a given period of time. Throughput is usually measured in megabits (1,000,000 bits) per second, or Mbps. The physical nature of every transmission media determines its potential throughput.

Front 111

transceiver

Back 111

A device that transmits and receives signals.

Front 112

transmission

Back 112

In networking, the application of data signals to a medium or the progress of data signals over a medium from one point to another.

Front 113

transmit

Back 113

To issue signals to the network medium.

Front 114

twist ratio

Back 114

The number of twists per meter or foot in a twisted pair cable.

Front 115

twisted pair

Back 115

A type of cable similar to telephone wiring that consists of color-coded pairs of insulated copper wires, each with a diameter of 0.4 to 0.8 mm, twisted around each other and encased in plastic coating.

Front 116

unpopulated segment

Back 116

A network segment that does not contain end nodes, such as workstations. Unpopulated segments are also called link segments.

Front 117

UTP (unshielded twisted pair)

Back 117

A type of cabling that consists of one or more insulated wire pairs encased in a plastic sheath. As its name implies, UTP does not contain additional shielding for the twisted pairs. As a result, UTP is both less expensive and less resistant to noise than STP.

Front 118

vertical cross-connect

Back 118

Part of a network’s backbone that supplies connectivity between a building’s floors. For example, vertical cross-connects might connect an MDF and an IDF or IDFs and telecommunications closets within a building.

Front 119

volt

Back 119

The measurement used to describe the degree of pressure an electrical current exerts on a conductor.

Front 120

voltage

Back 120

The pressure (sometimes informally referred to as the strength) of an electrical current.

Front 121

wavelength

Back 121

The distance between corresponding points on a wave’s cycle. Wavelength is inversely proportional to frequency.

Front 122

WDM (wavelength division multiplexing)

Back 122

A multiplexing technique in which each signal on a fiber-optic cable is assigned a different wavelength, which equates to its own subchannel. Each wavelength is modulated with a data signal. In this manner, multiple signals can be simultaneously transmitted in the same direction over a length of fiber.

Front 123

zipcord cable

Back 123

A relatively short fiber-optic cable in which two strands are arranged side by side in conjoined jackets, enabling full-duplex communication.