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Chapter 3 - Transmission Basics & Network Media - Key Terms
Network + Guide to Networks, 5th Edition
129
Computer Networking
Undergraduate 1
05/23/2013

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Term
1 gigabit per second (Gbps)
Definition
1,000,000,000 bits per second.
Term
1 kilobit per second (Kbps)
Definition
1000 bits per second.
Term
1 megabit per second (Mbps)
Definition
1,000,000 bits per second.
Term
1 terabit per second (Tbps)
Definition
1,000,000,000,000 bits per second.
Term
100 block
Definition
Part of an organization’s cross-connect facilities, a type of punch-down block designed to terminate Cat 5 or better twisted pair wires.
Term
100 pair wire
Definition
UTP supplied by a telecommunications carrier that contains 100 wire pairs.
Term
10Base-2 See Thinnet.
Definition
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.
Term
10Base-5 See Thicknet.
Definition
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.
Term
25 pair wire
Definition
UTP supplied by a telecommunications carrier that contains 25 wire pairs.
Term
66 block
Definition
Part of an organization’s cross-connect facilities, a type of punch-down block used for many years to terminate telephone circuits. It does not meet Cat 5 or better standards, and so it is infrequently used on data networks.
Term
alien cross talk
Definition
EMI interference induced on one cable by signals traveling over a nearby cable.
Term
AM (amplitude modulation)
Definition
A modulation technique in which the amplitude of the carrier signal is modified by the application of a data signal.
Term
amplifier
Definition
A device that boosts, or strengthens, an analog signal.
Term
amplitude
Definition
A measure of a signal’s strength.
Term
analog
Definition
A signal that uses variable voltage to create continuous waves, resulting in an inexact transmission.
Term
attenuation
Definition
The extent to which a signal has weakened after traveling a given distance.
Term
AWG (American Wire Gauge)
Definition
A standard rating that indicates the diameter of a wire, such
as the conducting core of a coaxial cable.
Term
bandwidth
Definition
A measure of the difference between the highest and lowest frequencies that a medium can transmit.
Term
baseband
Definition
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.
Term
bend radius
Definition
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.
Term
binary
Definition
A system founded on using 1s and 0s to encode information.
Term
bit (binary digit)
Definition
A bit equals a single pulse in the digital encoding system. It may have only one of two values: 0 or 1.
Term
BNC (Bayonet Neill-Concelman, or British Naval Connector)
Definition
A standard for coaxial cable connectors named after its coupling method and its inventors.
Term
BNC connector
Definition
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.
Term
braiding
Definition
A braided metal shielding used to insulate some types of coaxial cable.
Term
broadband
Definition
A form of transmission in which signals are modulated as radiofrequency 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.
Term
broadcast
Definition
A transmission that involves one transmitter and multiple, undefined receivers.
Term
byte
Definition
Eight bits of information. In a digital signaling system, broadly speaking, one byte
carries one piece of information.
Term
cable plant
Definition
The hardware that constitutes the enterprise-wide cabling system.
Term
capacity
Definition
See throughput.
Term
Cat
Definition
Abbreviation for the word category when describing a type of twisted pair cable. For example, Category 3 unshielded twisted pair cable may also be called Cat 3.
Term
Cat 3 (Category 3)
Definition
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 has typically been used for 10-Mbps Ethernet or 4-Mbps token ring networks. Network administrators are gradually replacing Cat 3 cabling with Cat 5 to accommodate higher throughput. Less expensive than Cat 5.
Term
Cat 4 (Category 4)
Definition
A form of UTP that contains four wire pairs and can support up to 16- Mbps throughput. Cat 4 may be used for 16-Mbps token ring or 10-Mbps Ethernet networks. It is guaranteed for data transmission up to 20 MHz and provides more protection against cross talk and attenuation than Cat 1, Cat 2, or Cat 3.
Term
Cat 5 (Category 5)
Definition
A form of UTP that contains four wire pairs and supports up to 100- Mbps throughput and a 100-MHz signal rate.
Term
Cat 5e (Enhanced Category 5)
Definition
A higher-grade version of Cat 5 wiring that contains high- quality 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.
Term
Cat 6 (Category 6)
Definition
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.
Term
Cat 6e (Enhanced Category 6)
Definition
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 6e is capable of a 550-MHz signaling rate and can reliably transmit data at multi-gigabit per second rates.
Term
Cat 7 (Category 7)
Definition
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.
Term
channel
Definition
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).
Term
cladding
Definition
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.
Term
coaxial cable
Definition
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.
Term
conduit
Definition
The pipeline used to contain and protect cabling. Conduit is usually made from metal.
Term
connectors
Definition
The pieces of hardware that connect the wire to the network device, be it a file server, workstation, switch, or printer.
Term
core
Definition
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.
Term
crossover cable
Definition
A twisted pair patch cable in which the termination locations of the transmit and receive wires on one end of the cable are reversed.
Term
cross talk
Definition
A type of interference caused by signals traveling on nearby wire pairs infringing on another pair’s signal.
Term
DB-9 connector
Definition
A type of connector with nine pins that’s commonly used in serial communication that conforms to the RS-232 standard.
Term
DB-25 connector
Definition
A type of connector with 25 pins that’s commonly used in serial communication that conforms to the RS-232 standard.
Term
DCE (data circuit-terminating equipment)
Definition
A device, such as a multiplexer or modem, that processes signals. DCE supplies a clock signal to synchronize transmission between DTE and DCE.
Term
demarcation point (demarc)
Definition
The point of division between a telecommunications service carrier’s network and a building’s internal network.
Term
demultiplexer (demux)
Definition
A device that separates multiplexed signals once they are received and regenerates them in their original form.
Term
digital
Definition
As opposed to analog signals, digital signals are composed of pulses that can have a
value of only 1 or 0.
Term
DTE (data terminal equipment)
Definition
Any end-user device, such as a workstation, terminal (essentially a monitor with little or no independent data-processing capability), or a console (for example, the user interface for a router).
Term
DWDM (dense wavelength division multiplexing)
Definition
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.
Term
EMI (electromagnetic interference)
Definition
A type of interference that may be caused by motors,
power lines, televisions, copiers, fluorescent lights, or other sources of electrical activity.
Term
entrance facilities
Definition
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.
Term
F-type connector
Definition
A connector used to terminate coaxial cable used for transmitting television and broadband cable signals.
Term
FDM (frequency division multiplexing)
Definition
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.
Term
ferrule
Definition
A short tube within a fiber-optic cable connector that encircles the fiber strand and keeps it properly aligned.
Term
fiber-optic cable
Definition
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 wave- division multiplexing to carry multiple signals.
Term
FM (frequency modulation)
Definition
A method of data modulation in which the frequency of the carrier signal is modified by the application of the data signal.
Term
frequency
Definition
The number of times that a signal’s amplitude changes over a fixed period of time, expressed in cycles per second, or hertz (Hz).
Term
full-duplex
Definition
A type of transmission in which signals may travel in both directions over a medium simultaneously. May also be called, simply, “duplex.”
Term
half-duplex
Definition
A type of transmission in which signals may travel in both directions over a medium, but in only one direction at a time.
Term
hertz (Hz)
Definition
A measure of frequency equivalent to the number of amplitude cycles per second.
Term
IDF (intermediate distribution frame)
Definition
A junction point between the MDF and concentrations of fewer connections—for example, those that terminate in a telecommunications closet.
Term
impedance
Definition
The resistance that contributes to controlling an electrical signal. Impedance is measured in ohms.
Term
latency
Definition
The delay between the transmission of a signal and its receipt.
Term
LC (local connector)
Definition
A connector used with single-mode or multimode fiber-optic cable.
Term
MDF (main distribution frame)
Definition
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.
Term
media converter
Definition
A device that enables networks or segments using different media to interconnect and exchange signals.
Term
MMF (multimode fiber)
Definition
A type of fiber-optic cable that contains a core with a diameter between 50 and 100 microns, through which many pulses of light generated by a light- emitting diode (LED) travel at different angles.
Term
modem
Definition
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.
Term
modulation
Definition
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.
Term
MT-RJ (mechanical transfer-registered jack)
Definition
A connector used with single-mode or multimode fiber-optic cable.
Term
multiplexer (mux)
Definition
A device that separates a medium into multiple channels and issues signals to each of those subchannels.
Term
multiplexing
Definition
A form of transmission that allows multiple signals to travel simultaneously over one medium.
Term
NEXT (near end cross talk)
Definition
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.
Term
noise
Definition
The unwanted signals, or interference, from sources near network cabling, such as electrical motors, power lines, and radar.
Term
nonbroadcast point-to-multipoint transmission
Definition
A communications arrangement in which a single transmitter issues signals to multiple, defined recipients.
Term
optical loss
Definition
The degradation of a light signal on a fiber-optic network.
Term
overhead
Definition
The nondata information that must accompany data in order for a signal to be properly routed and interpreted by the network.
Term
patch cable
Definition
A relatively short section (usually between 3 and 25 feet) of cabling with connectors on both ends.
Term
patch panel
Definition
A wall-mounted panel of data receptors into which cross-connect patch cables from the punch-down block are inserted.
Term
phase
Definition
A point or stage in a wave’s progress over time.
Term
plenum
Definition
The area above the ceiling tile or below the subfloor in a building.
Term
point-to-point
Definition
A data transmission that involves one transmitter and one receiver.
Term
point-to-multipoint
Definition
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.
Term
populated segment
Definition
A network segment that contains end nodes, such as workstations.
Term
punch-down block
Definition
A panel of data receptors into which twisted pair wire is inserted, or punched down, to complete a circuit.
Term
regeneration
Definition
The process of retransmitting a digital signal. Regeneration, unlike amplification, repeats the pure signal, with none of the noise it has accumulated.
Term
repeater
Definition
A device used to regenerate a signal.
Term
RFI (radiofrequency interference)
Definition
A kind of interference that may be generated by broadcast signals from radio or TV towers.
Term
RG-6
Definition
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.
Term
RG-8
Definition
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.
Term
RG-58
Definition
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.
Term
RG-59
Definition
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.
Term
RJ-11 (registered jack 11)
Definition
The standard connector used with unshielded twisted pair cabling (usually Cat 3 or Level 1) to connect analog telephones.
Term
RJ-45 (registered jack 45)
Definition
The standard connector used with shielded twisted pair and unshielded twisted pair cabling.
Term
rollover cable
Definition
A type of cable in which the terminations on one end are exactly the reverse of the terminations on the other end. It is used for serial connections between routers and consoles or other interfaces.
Term
RS-232 (Recommended Standard 232)
Definition
A Physical layer standard for serial communications,
as defined by EIA/TIA.
Term
RTT (round trip time)
Definition
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.
Term
SC (subscriber connector or standard connector)
Definition
A connector used with single-mode or multimode fiber-optic cable.
Term
serial
Definition
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.
Term
serial cable
Definition
A cable, such as an RS-232 type, that permits serial data transmission.
Term
sheath
Definition
The outer cover, or jacket, of a cable.
Term
simplex
Definition
A type of transmission in which signals may travel in only one direction over a medium.
Term
SMF (single-mode fiber)
Definition
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.
Term
ST (straight tip)
Definition
A connector used with single-mode or multimode fiber-optic cable.
Term
statistical multiplexing
Definition
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.
Term
STP (shielded twisted pair)
Definition
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.
Term
straight-through cable
Definition
A twisted pair patch cable in which the wire terminations in both connectors follow the same scheme.
Term
structured cabling
Definition
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.
Term
subchannel
Definition
One of many distinct communication paths established when a channel is multiplexed or modulated.
Term
TDM (time division multiplexing)
Definition
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.
Term
telecommunications closet
Definition
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.
Term
throughput
Definition
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.
Term
transceiver
Definition
A device that transmits and receives signals.
Term
transmission
Definition
In networking, the application of data signals to a medium or the progress of data signals over a medium from one point to another.
Term
transmit
Definition
To issue signals to the network medium.
Term
twist ratio
Definition
The number of twists per meter or foot in a twisted pair cable.
Term
twisted pair
Definition
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.
Term
unpopulated segment
Definition
A network segment that does not contain end nodes, such as workstations. Unpopulated segments are also called link segments.
Term
UTP (unshielded twisted pair)
Definition
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.
Term
vertical cross-connect
Definition
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.
Term
volt
Definition
The measurement used to describe the degree of pressure an electrical current exerts on a conductor.
Term
voltage
Definition
The pressure (sometimes informally referred to as the strength) of an electrical current.
Term
wavelength
Definition
The distance between corresponding points on a wave’s cycle. Wavelength is
inversely proportional to frequency.
Term
WDM (wavelength division multiplexing)
Definition
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.
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