Vocab Ch. 1-4 Flashcards
1
Q
computer network
A
An interconnection of computers and computing equipment using either wires or radio waves and can share data and computing resources.
2
Q
wireless
A
Computer networks that use radio waves and can involve broadcast radio, microwaves, or satellite transmissions.
3
Q
personal area networks
A
(PANs) - Networks spanning several meters around an individual. Includes devices such as laptop computers, personal digital assistants, and wireless connections.
4
Q
local area networks
A
(LANs) - Networks spanning a room, a floor within a building, a building, or a campus.
5
Q
metropolitan area networks
A
(MANs) - Networks that serve an area up to roughly 50km. They are high-speed networks that interconnect businesses with other businesses and the Internet.
6
Q
wide area networks
A
(WANs) - Large networks encompassing parts of states, multiple states, countries, the world.
7
Q
data
A
Information that has been translated into a form more conductive to storage, transmission, and calculation.
8
Q
data communications
A
The transfer of digital or analog data using digital or analog signals.
9
Q
multiplexing
A
The transmission of multiple signals on one medium. For a medium to transmit multiple signals simultaneously, the signals must be altered so that they do not interfere with one another.
10
Q
compression
A
Another technique that can maximize the amount of data sent over a medium. It involves squeezing data into a smaller package, thus reducing the amount of time (as well as storage space) needed to transmit the data.
11
Q
convergence
A
The margin of voice and data networks.
12
Q
network management
A
The design, installation, and support of a network and its hardware and software.
13
Q
workstations
A
Personal computers/microcomputers (desktops, laptops, netbooks, handhelds, etc.) where users reside.
14
Q
servers
A
The computers that store network software and shared or private files.
15
Q
switches
A
The collection points for the wires that interconnect the workstations.
16
Q
routers
A
The connecting devices between local area networks and wide area networks. It also performs security functions and must be properly programmed to accept or reject certain types of incoming and outgoing data packets.
17
Q
nodes
A
The computing devices that allow workstations to connect to the network and that make the decisions about where to route a piece of data.
18
Q
subnetwork
A
Also know as a cloud, consists of the nodes and transmission lines, collected into a cohesive unit.
19
Q
TCP/IP
A
(Transmission Control Protocol/Internet Protocol) - The language computers use to send & received data on the Internet.
20
Q
client/server system
A
A user at a microcomputer, or client machine, issues a request for some form of data or service. The request travels across the system to a server that contains a large repository of data and/or programs. The server fills the request and returns the results to the client, displaying the results on the client’s monitor.
21
Q
computer terminal
A
A device that was essentially a keyboard and screen with no long-term storage capabilities and little, if any, processing power.
22
Q
protocol
A
Set of rules used by communication devices.
23
Q
convergence
A
When different network applications and the technologies that support them converge into a single technology capable of supporting various applications.
24
Q
types of convergence
A
1) technological
2) protocol
3) industrial
25
technological convergence
When two different technologies, such as the use of computers and modems to transmit data over the telephone system. Voice transmission services converged with data transmission services.
26
protocol convergence
When two different protocols converge to become one protocol.
27
industrial convergence
Where separate companies converge to provide a better service.
28
network architecture
Or communications model, places the appropriate network pieces in layers. The layers define a model for the functions or services that need to be preformed.
29
Open Systems Interconnection
(OSI) - A theoretical networking model.
30
TCP/IP Layers OSI Layers
TCP/IP OSI
1) application 1) Application
2) transport 2)Presentation
3) network 3) Session
4) network access 4) Transport
5) physical 5) Network
6) Data Link
7) Physical
31
TCP/IP - application layer
The top layer, supports the network applications and might in some cases include additional services such as encryption or compression.
32
Hypertext Transfer Protocol
(HTTP) - Allows Web browsers and servers to send and receive World Wide Web pages
33
Simple Mail Transfer Protocol
(SMTP) - Allows users to send and receive electronic mail.
34
File Transfer Protocol
(FTP) - Transfers files from one computer system to another.
35
Telnet
Allow a remote user to log in to another computer system
36
Simple Network Management Protocol
(SNMP) - Allows the numerous elements within a computer network to be managed from a single point.
37
TCP/IP - transport layer
Commonly uses TCP to maintain and error-free end-to-end connection. Includes error control-information in case one packet from a sequence of packets does not arrive at the final destination, and packet sequencing info so that all the packets stay in the proper order. It is only used at the two end points.
38
TCP/IP - network layer
Sometimes called the Internet layer or IP layer, is used to transfer data within and between networks.
39
Internet Protocol
(IP) - The software that prepares a packet of data so that it can move from one network to another on the Internet or within a set of corporate networks. Generates the network addresses necessary for the system to recognize the nest intended receiver.
40
TCP/IP - network access layer
Often called the data link layer - Deals with passing packets through the Internet, then it gets the data from the user workstation to the Internet.
41
frame
A data packet in the network access layer that contains an identifier that signals the beginning and end of the frame, as well as spaces for control information and address information.
42
TCP/IP - physical layer
The layer in which the actual transmission of data occurs.
43
OSI - application layer
Top layer, contains the application using the network.
44
OSI - presentation layer
Performs a series of miscellaneous functions necessary for presenting the data package properly to the sender and receiver, including encryption and decryption.
45
OSI - session layer
Establishes the sessions between users. It can also provide token management.
46
token management
A service that controls which user's computer talks during the current session by passing a software token back and forth.
47
synchronization points
Backup points used in case of errors of failures.
48
OSI - transport layer
It ensures that the data packet that arrives at the final destination is identical to the data packet that left the originating station.
49
OSI - network layer
Responsible for getting the data packets from router to router through the network.
50
OSI - data link layer
Responsible for taking data from the network layer and transforming it into a frame.
51
OSI - physical layer
The bottom layer - Handles the transmission of bits over a communications channel.
52
logical connection
A nonphysical connection between sender and receiver that allows an exchange of commands and responses.
53
physical connection
The only direct connection between sender and receiver. This is where the actual 1s and 0s are transmitted over wires or airwaves.
54
encapsulation
The addition of control information to a packet as it moves through the layers of TCP/IP or OSI.
55
Modulation
The process of sending data over a signal by varying either its amplitude, frequency, or phase.
56
digitization
Converting analog data to digital signals.
57
transmitter
The originating device.
58
receiver
The destination device.
59
data
Entities that convey meaning with a computer or system.
60
signals
Electric and electromagnetic impulses used to encode and transmit data.
61
analog data & analog signals
Represented as continuous waveforms that can be at an infinite number of points between some given minimum and maximum.
62
noise
Unwanted electrical or electromagnetic energy that degrades the quality of signals and data.
63
digital data & digital signals
Composed of a discrete or fixed number of values, rather than a continuous or infinite number of values. Digital data takes the form of binary 1s and 0s.
64
The three basic components of digital signals
1) amplitude
2) frequency
3) phase
65
amplitude
The height of the wave above (or below) a given reference point.
66
frequency
Represented in hertz (Hz). The number of times a signal makes a complete cycle within a given time frame.
67
period
The length, or time interval, of one cycle. (1/frequency)
68
spectrum
The range of frequencies that a signal spans from minimum to maximum.
69
bandwidth
The absolute value of the difference between the lowest and highest frequencies.
70
effective bandwidth
Less than the bandwidth, it is the absolute value of the difference between lowest and highest frequencies that give the best data transmission.
71
phase
The position of the waveform relative to a given moment in time, or relative to time zero.
72
phase change
Or phase shift - Involves jumping forward (or backward) in the waveform at a given moment of time.
73
attenuation
The loss of power, or loss of signal strength.
74
Decibel (DB)
A relative measure of signal loss or gain and is used to measure the logarithmic loss or gain of a signal
75
amplification
The opposite attenuation - the gain of power or gain of signal strength.
76
modulation
The process of sending data over a signal by varying either its amplitude, frequency, or phase.
77
nonreturn to zero-level
(NRZ-L) Digital coding transmits 1s as zero voltages and 0s as positive voltages.
Pros: Simple and inexpensive
Cons: Long sequences of zeros in the data produce a signal that does not change, making it difficult to determine where one bit ends and the next one begins. Needs a clock.
78
nonreturn to zero inverted
(NRZI) Has a voltage change at the beginning of a 1 and no voltage change at the beginning of a 0.
Pros: Looks for voltage change to determine 1 or 0.
Cons: Long sequences of zeros in the data produce a signal that does not change, making it difficult to determine where one bit ends and the next one begins. Needs a clock.
79
Manchester encoding scheme
To transmit a 1, the signal changes from low to high in the middle of the interval, and to transmit a 0, the signal changes from high to low in the middle of the interval.
Pros: Ensures each bit has some type of signal change. Therefor, referred to as self-clocking.
Cons: Roughly half the time, there will be two transitions during each bit.
80
differential Manchester digital encoding scheme
If there is a transition at the beginning of the interval, then a 0 is being transmitted. If there is no transition at the beginning of the interval, then a 1 is being transmitted.
81
baud rate
The number of times a signal changes value per second.
82
data rate
Measured in bits per second (bps), it is a measurement of the number of bits transmitted in a set period of time.
83
bipolar-AMI
Uses three voltage levels. When a device transmits a binary 0, a zero voltage is transmitted. When the device transmits a binary 1, either a positive or negative voltage is transmitted.
Pros: When all of the voltages are added together after a long transmission, there should be a total voltage of zero.
Cons: Long string of zeros problem. Hardware must be able to produce negative voltages.
84
4B/5B
Takes 4 bits of data, converts the 4bits into a unique 5-bit sequence, and encodes the 5 bits using NRZI.
Pros: Eliminates long strings of zeros. Only 20% overhead.
Cons: There is a 20% overhead compared to NRZI.
85
amplitude shift keying
A data value of 1 and a data value of o are represented by two different amplitudes of a signal. During each period, the amplitude of the signal is constant. Not restricted to two possible amplitude levels. Not used in systems that require a high data rate.
86
frequency shift keying
Uses two different frequency ranges to represent data values of 0 and 1. Not used in systems that require a high data rate.
87
intermodulation distortion
A phenomenon that occurs when the frequencies of two or more signals mix together and create new frequencies.
88
phase shift keying
Represents 0s and 1s by different changes in the phase of a waveform. Not affected by amplitude changes, nor are they affected by intermodulation distortions. Less susceptible to notice and can be used at higher frequencies.
89
quadrature phase shift keying
Incorporates four different phase angles, each of which represents 2 bits. Has double the efficiency of simple phase shift keying.
90
quadrature amplitude modulation
Two different amplitudes are applied on each of four phase angles, resulting in 16 different combinations. Commonly employed in higher-speed modems and uses each signal change to represent 4 bits. The bps of data transmitted is 4 times the baud rate.
91
pulse code modulation
(PCM) - Converts analog data to a digital signal. Using a codec, converts the analog data to a digital signal by tracking the analog waveform and taking "snapshots" of the analog data at fixed intervals.
92
pulse amplitude modulation
(PAM) - Tracking an analog waveform and converting it to pulses that represent the wave's height above (or below) a threshold.
93
quantization levels
The number of divisions on the y-axis for PAM.
94
quantization erro
Also known as quantization noise - Error introduced by approximating the value of the analog signal to the closest quantization level.
95
sampling rate
The frequency at which the snapshots are taken. Too many can be inefficient, too few can result in a distortion of the original waveform.
96
delta modulation
A codec tracks the incoming analog data by assessing up or down "steps." During each time period, the codec determines whether the waveform has risen one delta step or dropped one delta step. If the waveform rises one delta step, a 1 is transmitted. If it drops one delta step, a 0 is transmitted. It is quicker than pulse code modulation. However, if it drops or rises too quickly, the codec can not keep up. Also, a constant waveform creates quantizing noise.
97
slope overload noise
When the analog waveform rises or drops too quickly for the codec to keep up.
98
data code
The set of textual characters or symbols and their corresponding binary patterns.
99
Extended Binary Coded Decimal Interchange Code
EBCDIC - An 8-bit code with 256 possible combinations of textual symbols. Used by IBM mainframes.
100
American Standard Code for Information Interchange
ASCII - A government standard in the US and is one of the most widely used data codes in the world. There are a few different versions, including a 7-bit version with 128 possible combinations.
101
unicode
A coding technique that provides a unique coding value for every character of every language.
102
Two categories of communications media
1) physical or conducted media - such as cell phone lines
| 2) radiated or wireless media - such as cell phones
103
twisted pair wire
Comes as two or more pairs of single-conductor insulated copper wires that have been twisted around each other.
104
crosstalk
When a current or signal in one wire produces an unwanted current or signal in a second wire.
105
CAT 1 cable
Standard telephone wire. No twisting, more noise
106
CAT 2 cable
Used for phone and low-speed LANs. Has some twisting, less noise.
107
CAT 3 cable
Designed to transmit 10 Mbps over a LAN for distances up to 100 meters (328 feet). Mainly used for phone.
108
repeater
A device that generates a new signal by creating an exact replica of the original signal.
109
CAT 4 cable
Designed to transmit 20 Mbps of data for distances up to 100 meters. Rarely sold anymore.
110
CAT 5 cable
Twisted pair cable designed to transmit 100 Mbps of data for up to 100 meters. Specifically for a 100 MHz signal. Has a higher number of twists per inch than CAT 1 - 4 wires, so less noise.
111
CAT 5e cable
Similar to CAT 5 but the specification requires four pairs of wires and provides designations for the connectors on the end of the wires, patch cords, and other possible components. In other worlds, a more specific specification. 100 meters
112
CAT 6 cable
Designed for a signal as high as 250 MHz. Speeds from 250 - 1000 Mbps. 100 meters
113
CAT 7 cable
Newest addition. The cable is heavily shielded. Can support up to 600 MHz and speeds up to 10 Gbps. 100 meters
114
Coaxial cable
The simplest form, is a single wire wrapped in foam insulation, surrounded by a braided metal shield. Great for transmitting analog signals with a wide range of frequencies and so can carry large numbers of video channels.
115
Baseband coaxial
Uses digital signaling in which the cable carries only one channel of digital data.
116
Broadband coaxial
Typically transmits analog signals and is capable of supporting multiple channels of data simultaneously.
117
Thick coaxial
6-18mm
118
Thin coaxial
4mm
119
Coaxial RG-58
Used for baseband Ethernet LANs
120
Coaxial RG-6
Used for cable TV.
121
fiber-optic cable
A thin glass cable, a little thicker than a human hair, surrounded by a plastic coating. Is capable of transmitting at speed over 100 Gbps over several kilometers. Real world use is closer to 10 Gbps and 300 meters.
122
photo diode
The light source commonly used for transmitting data over fiber-optic cable.
123
photo receptor
An optic sensor used to receive data transmitted over fiber-optic cable.
124
Additional advantages of fiber-optic cable
| Disadvantages
Advantages
1) Virtually impossible to wiretap.
2) No noise generated from electromagnetic signals.
Disadvantages
1) Light pulses can travel in one direction only. Which means that for two way communication, two cables are needed.
2) High cost.
125
backbone of a network
The main connecting cable that runs from one end of the installation to another.
126
photonic fiber
A type of medium used in fiber optic cables that has a honeycomb pattern which allows the light to travel through the air in the bubbles. A reflective surface more reflective than a mirror is used to prevent the material surround the cable from absorbing the light. Allows for transmission of data over distances at least 10 times that of current fiber-optic.
127
reflection
When a light signal inside the cable bounces off the cable wall and back into the cable.
128
refraction
When a light signal passes from the core of the cable into the surrounding material.
129
single-mode transmission
Uses a very thin fiber-optic cable and a very focussed light source such as a laser. Allows for a very fast signal with very little signal degradation. Is expensive.
130
multimodal transmission
Uses a slightly thinker cable and an unfocused light source such as a LED. This causes more noise but it is less expensive and it is what is normally used for LANs.
131
right-of-way
The legal capability of a business or person to install a wire or cable across someone else's property.
132
Terrestrial microwave
Transmission systems that transmit tightly focused beams of radio signals from one ground-based microwave transmission antenna to another. Often used for telephone communications and business intercommunications. Uses line-of-sight transmission.
133
line-of-sight transmission
The category of transmission systems which require each antenna to be in sight of the next antenna in order to receive the signal.
134
satellite microwave
Similar to terrestrial microwave except that it travels from the surface of the Earth to a satellite and back to another ground station on Earth.
135
uplink
To send data to a satellite.
136
downlink
To receive data from a satellite.
137
propagation delay
The transmission time from ground station to satellite and back to ground station.
138
Low-Earth-orbit satellite
(LEO) - Closest to earth, from 100 - 1000 miles from Earth. Must orbit the Earth and therefore the point on Earth that the satellite is over changes depending on where it is in its orbit.
139
Middle-Earth-orbit satellite
(MEO) - Roughly 1000 - 3000 miles from Earth. Must orbit the Earth and therefore the point on Earth that the satellite is over changes depending on where it is in its orbit.
140
global positioning system
(GPS) - A system of 24 satellites launch by the U.S. Department of Defense and used for identifying locations on Earth by triangulating signals.
141
Geosynchronous-Earth-Orbit
(GEO) - 36,000 kilometers (22,300 miles) from Earth and are always positioned over the same point on Earth.
142
highly elliptical orbit satellite
(HEO) - The orbit follows an elliptical pattern.
143
mobile service areas
(MSAs) - Used by the FCC as an alternative to giving each cellular service provider a different frequency, they are more than 700 different markets or zones.
144
Advanced Mobile Phone Service
(AMPS) - The first-generation mobile phone service. It used frequency division multiplexing technology. The cellular equivalent to the "plane old telephone system."
145
Digital Advanced Mobile Phone Service
(D-AMPS) - Newer, digital equivalent to AMPS. Used time division multiplexing in addition to frequency division multiplexing.
146
Personal Communications Services
(PCS) - Second generation cell phone technology.
147
Time Division Multiple Access
(TDMA) - One of three incompatible PCS technologies, it divides the available user channels by time, giving each transmitting cell phone a brief turn to transmit.
148
Code Division Multiple Access
(CDMA) - One of three incompatible PCS technologies, it spreads the transmission of a cell phone signal over a wide range of frequencies, using mathematical values. It is based on a spread spectrum technology.
149
Global System for Mobile
(GSM) - One of three incompatible PCS technologies, uses a different form of TDMA technology.
150
General Packet Radio Service
(GPRS) - A faster network which took the place of GSM.
151
LTE Advances
The fourth generation of cellular service.
152
broadband wireless system
Also known as the wireless local loop or fixed-point wireless, is used to deliver Internet services into homes and businesses.
153
WiMax
Broadband wireless transmission technology that was designed to deliver high-speed Internet access to homes and small businesses to compete with DSL.
154
Bluetooth
A protocol for a wireless technology that uses low-power, short-range radio frequencies to communicate between two or more devices.
155
piconet
A small network with eight or fewer devices.
156
scatternet
The interconnection of multiple piconets.
157
wireless fidelity
(Wi-Fi) - Wireless technology used for LANs. Uses the 2.4-GHz and 5-GHz spectrums. The most recent version of protocol the is in use is IEEE 802.11(ac).
158
Infrared transmission
IR - Works similar to TV remotes but with a focused ray of light. Line-of-sight.
159
ZigBee
A relatively new wireless technology used to connect smaller devices. (The Internet of Things)
160
media selection criteria
The principal factors you should consider before making the final choice on networking technology include:
1) cost
2) speed
3) expandability
4) distance
5) environment
6) security
161
propagation speed
The speed at which a signal moves through a medium.
162
Three popular data link layer configurations:
1) asynchronous connections
2) synchronous connections
3) isochronous connections
163
interfacing
The process of providing all the proper interconnections between a computer and a peripheral.
164
basic characteristics of interface standards
1) They have been created and approved by an acceptable standards-making organization.
2) They can consist of one to four components:
1) electrical component
2) mechanical component
3) functional component
4) procedural component
165
de facto standard
A nonstandard protocol that becomes so popular that other companies start using it.
166
interface standards - electrical component
Deals with voltages, line capacitance, and other electrical issues.
167
interface standards - mechanical component
Deals with items such as the connector or plug description.
168
interface standards - functional component
Describes the function of each pin (which is referred to as a circuit when you also take into account the signal that travels through the pin and wire)
169
interface standards - procedural component
Describes how the particular circuits are used to perform an operation.
170
full-duplex connection
A connection in which both sender and receiver may transmit a the same time.
171
half-duplex connection
A connection that allows only one side or the other (either the sender or the receiver) to transmit at one time.
172
Universal Serial Bus
(USB) - A modern standard for interconnecting peripheral devices. It is a digital interface that uses a standardized connector for all serial and parallel type devices.
173
daisy-chaining
A technique of connecting a device to each subsequent device instead of the computer.
174
IEEE 1394
Also known as Firewire, was used mainly for hard drives and video equipment and it a competing standard to USB. Supports two types of data connections: asynchronous and isochronous.
175
Thunderbolt
Currently found on Apple computers and provides 10-Gbps connections. Uses the same connector as the Mini DisplayPort.
176
Small Computer System Interface
(SCSI) - Pronounced "skuzzy", it is a technique for interfacing a computer to a high-speed device such as hard disk drivers, tape drives, CDs, and DVDs.
177
Internet SCSI
(ISCSI) - A technique for interfacing disk storage to a computer via the Internet.
178
InfiniBand
A serial connection or bus that can carry multiple channels of data at the same time.
179
Fibre Channel
Similar to InfiniBand, in that it is a serial connection. Connects a computer to multiple input/output devices.
180
asynchronous connection
One of the simplest examples of a data link protocol and is found primarily in microcomputer-to-dial-up-modem and terminal-to-modem connections.
A single character, or byte of data, is the unit of transfer between sender and receiver. The sender prepares a data character for transmission, transmit that character, and then begins preparing the next data character. There can be an indefinite amount of time between transmissions.
Pros:
Simple to generate the start, stop, and parity bits and requires little or no hardware or software.
Cons:
30% of the bits transmitted are used as check bits, not very efficient and results in slow transfer rates.
181
frame
A small packet of data created by adding a few bits of information to the data bits of the character being sent.
182
asynchronous connection - start bit
Always a logic 0, is added to the beginning of the character and informs the receiver that an incoming data frame is arriving.
183
asynchronous connection - stop bits
Bits added to the end of the data character, one or two, which are always logic 1s and signal the end of the frame.
184
asynchronous connection - parity bit
Can indicate odd parity or even parity, it performs an error check on only the data bits. This error check is achieved by adding a 0 or 1 such that an even or odd number of 1s is maintained.
185
synchronous connection
The unit of transmission is a sequence of characters and can be thousands of characters in size.
Pros:
Much faster and and more efficient.
Cons:
Needs to have a system to keep the sender and receiver in sync.
186
synchronous connection - start sequence
(flag) - Typically 8 bits (a byte) in length and indicates the start of the frame.
187
synchronous connection - control byte
One or bits of control information which provides info about the enclosed data or provides status info pertaining to the sender or receiver or both.
188
synchronous connection - address
Indicated the destination of the frame, where it came from, or both.
189
synchronous connection - checksum
The error checking data that allows the receiver to make sure the frame is intact (information has not been lost or altered in some way).
190
synchronous connection - end sequence
(flag) - Typically 8 bits (a byte) in length and indicates the end of the frame.
191
isochronous connection
A special kind of data link connection used to support various types of real-time applications. Examples: streaming voice, video, and music.
Real-time applications are unique in that data must be delivered to a computer at just the right speed. Too slow and the data is distorted, too fast and the receiving computer may not be able to store all of the data before it is used.
Error checking is not used because there is not enough time to check, request, and receive new information.
192
point-to-point connection
A dirrect connection between a terminal and mainframe computer.
193
multipoint connection
A single wire with the mainframe connected on one end and multiple terminals connected on the other end.
194
polling
Successfully controls multiple terminals that share a contain to a mainframe computer so that only one terminal transmits at a time.
195
primary
The mainframe computer.
196
secondary
Any terminals.
197
roll-call polling
A polling method in which the primary polls each secondary, one at a time, in round-robin fashion.
198
hub polling
Polls only the first terminal (secondary) which then passes it on the the second terminal and so on.
199
selection
The primary creates a packet of data with the address of the intended terminal and transmits the packet.
