Ch4 Flashcards
(202 cards)
1
Q
Media access controls refer to the need to control when computers transmit
A
T
2
Q
The data link layer accepts messages from the network layer and controls the
hardware that transmits them.
A
T
3
Q
Only the sender of a data transmission needs to be concerned about the rules or
protocols that govern how it communicates with the receiver.
A
F
4
Q
As part of the five-layer network model used in this textbook, the data link layer sits directly
between:
a. the physical and the application layers
b. the network and the application layers
c. the network and transport layers
d. the physical and the application layers
e. the physical and the network layers
A
E
5
Q
Which of the following is true with respect to the data link layer?
a. It accepts streams of bits from the application layer.
b. It is responsible for getting a message from one computer to another (one node to
another) without errors.
c. It does not perform error detection.
d. It performs routing functions.
e. It organizes data from the physical layer and passes these coherent messages to the
application layer.
A
B
6
Q
____________ is not a function of a data link protocol.
a. Media access control
b. Message delineation
c. Amplitude shift keying
d. Indicating when a message starts and stops
e. Error control
A
C
7
Q
The first sublayer of the data link layer is the
a. logical link control sublayer
b. media access control sublayer
c. session sublayer
d. physical sublayer
e. transport sublayer
A
A. Second sublayer is Media Access Control
8
Q
What function does the Logical Link Control (LLC) sublayer perform within the Data Link Layer?
A) It converts data link layer PDUs into a stream of bits and controls the timing of transmission at the physical layer.
B) It ensures reliable, ordered, and error-checked delivery of data between communicating devices.
C) It establishes, maintains, and terminates connections between devices on a network.
D) It connects to and communicates with the network layer above.
A
D
9
Q
At the receiving end in the Media Access Control (MAC) sublayer, what is the main task performed?
A) Translating a stream of bits into a coherent PDU
B) Controlling the physical hardware of the network interface
C) Ensuring no errors have occurred during transmission
D) Establishing connections between network devices
A
A
10
Q
- What does the transmitting end do in the Logical Link Control (LLC) sublayer?
A) Surrounds the IP packet with an Ethernet frame
B) Controls when physical layer hardware can transmit bits
C) Ensures error-free transmission at the data link layer
D) Establishes connections between devices on a network
A
A
11
Q
What is the primary responsibility of the transmitting end in the Media Access Control (MAC) sublayer?
A) Translating data link layer PDUs into a coherent message
B) Controlling when physical layer hardware can transmit bits
C) Ensuring error-free transmission at the network layer
D) Establishing connections between devices on a network
A
B
12
Q
What is the primary task of the receiving end in the Logical Link Control (LLC) sublayer?
A) Removing the data link layer PDU and passing the contained message to the network layer
B) Controlling the physical hardware of the network interface
C) Ensuring the integrity of the IP packet
D) Establishing connections between network devices
A
A
13
Q
Which task is specifically associated with the transmitting end in the Logical Link Control (LLC) sublayer?
A) Translating a stream of bits into a coherent PDU
B) Surrounding the IP packet with a data link layer PDU
C) Ensuring error-free transmission at the physical layer
D) Establishing connections between network devices
A
B
14
Q
Which function is primarily associated with the Media Access Control (MAC) aspect of a data link layer protocol?
A) Detects and corrects transmission errors
B) Controls when computers transmit
C) Identifies the start and end of a message
D) Establishes connections between network devices
A
B
15
Q
What is the primary role of error control in a data link layer protocol?
A) Controls when computers transmit
B) Detects and corrects transmission errors
C) Identifies the start and end of a message
D) Establishes connections between network devices
A
B
16
Q
Which aspect of a data link layer protocol is responsible for ensuring that computers transmit data in an organized manner?
A) Error control
B) Media Access Control (MAC)
C) Message delineation
D) Connection establishment
A
B
17
Q
What aspect of a data link layer protocol determines the boundaries of individual messages?
A) Media Access Control (MAC)
B) Error control
C) Message delineation
D) Connection establishment
A
C
18
Q
What are the three major functions associated with a data link layer protocol?”
A) Media Access Control (MAC), Error control, Connection establishment
B) Error detection, Message delineation, Media Access Control (MAC)
C) Error control, Media Access Control (MAC), Message delineation
D) Connection establishment, Error control, Media Access Control (MAC)
A
C
19
Q
Most computer networks managed by a host mainframe computer tend to use a form
of media access control called contention.
A
F. Contention: Computers wait for the circuit to be free before transmitting their data
20
Q
With contention, a computer does not have to wait before it can transmit. A computer
can transmit at any time.
A
F. Computers wait for the circuit to be free before transmitting their data.
21
Q
Media access control is not very important in point-to-point with full duplex configuration.
A
T. In point-to-point full-duplex configurations, media access control is not needed because only two computers are on the circuit and can transmit simultaneously.
22
Q
Media access control is not very important in local area networks
A
F. MAC protocols can support networks ranging from small local area networks (LANs)
23
Q
Media access control is not very important in a point-to-point with a half-duplex
configuration
A
F
24
Q
What characteristic defines a multipoint circuit?
A) It uses different circuits for each connection.
B) It shares the same circuit among multiple connections.
C) It connects only two devices at a time.
D) It operates independently of other circuits.
A
B
25
Media access control is not very important in a multipoint configuration.
F
26
Media access control does not control when computers transmit.
F
27
In a contention, what defines a collision?
a) A computer's failure to transmit data.
b) When two or more computers attempt to transmit data simultaneously.
c) The loss of data during transmission.
d) When a computer overheats due to excessive network activity.
B
28
Contention is widely used with Ethernet local area networks.
T
29
Roll call polling is a type of contention approach to media access control
F
30
Controlled access MAC approaches work well in a large network with high usage
T
31
There are three commonly used controlled access techniques: access requests, access
demands, and polling
F. just 2: access request and polling
32
In general, controlled approaches work better than contention approaches for small
networks that have low usage
F
33
In general, controlled approaches work better than contention approaches for large
networks that have high usage
T
34
In general, controlled approaches work better than contention approaches for all sizes of networks
F
35
In general, controlled approaches do not require a host, server, or active monitor to
assign media access control.
F
36
In general, controlled approaches have many collisions
F
37
Which of the following is not a controlled access method of media access control?
a. Token passing
b. CSMA/CD
c. polling
d. roll call polling
e. hub polling
B
38
In general, controlled approaches:
a. work better than contention approaches for small networks that have low usage.
b. work better than contention approaches for large networks that have high usage.
c. work better than contention approaches for all sizes of networks.
d. do not require a host, server, or active monitor to assign media access control.
e. have many collisions.
B
39
Which of the following best describes controlled access in a network environment?
A) Every device on the network can transmit data simultaneously.
B) Multiple devices control access to the circuit.
C) One device controls the circuit and determines which clients can transmit at what time.
D) Access to the shared circuit is unregulated.
E) Controlled access relies on a decentralized approach for managing network traffic.
C. Controlled Access: One device controls the circuit and determines which clients can transmit at what time:
+Controls access to the shared circuit
+Acts like a stop light
40
What is the primary function of a controlled access device in a network?
A) Transmit data to all connected clients simultaneously
B) Regulate access to a shared circuit
C) Monitor network traffic for security threats
D) Increase the speed of data transmission
B.Controlled Access: One device controls the circuit and determines which clients can transmit at what time:
+Controls access to the shared circuit
+Acts like a stop light
41
What is the primary role of controlled access in a wireless LAN (Local Area Network)?
A) Regulating the speed of data transmission
B) Determining which computer has access to the base station
C) Encrypting all data transmissions for security
D) Monitoring the signal strength of connected devices
B
42
In a wireless LAN environment, what does the controlled access mechanism determine?
A) Which devices are allowed to connect to the internet
B) Which computer has access to the central base station at any given time
C) The range of the wireless network
D) The type of data protocols used for transmission
B
43
How does controlled access operate in a wireless LAN?
A) It allows all devices to transmit data simultaneously
B) It grants exclusive access to the base station for one computer at a time
C) It randomly assigns access privileges to connected devices
D) It restricts access to the network based on device location
B. Wireless access point = wireless LAN
44
Which device typically controls access in a wireless LAN?
A) Modem
B) Router
C) Access point (base station)
D) Network interface card (NIC)
C
45
What is the main benefit of using controlled access in a wireless LAN?
A) Increased network speed
B) Enhanced signal strength
C) Reduced interference and data collisions
D) Greater range of connectivity
C
46
In the access request technique, what action do client computers take when they want to transmit data?
A) They immediately start transmitting data.
B) They send a request to the controlling device.
C) They wait for permission from other client computers.
D) They disconnect from the network temporarily.
B
47
Which of the following is an example of a device that controls access to the shared circuit in wireless networks?
A) Modem
B) Router
C) Wireless access point
D) Network switch
C
48
How does the controlling device manage data transmission in the access request technique?
A) By allowing all client computers to transmit simultaneously
B) By granting permission for one client computer at a time to transmit
C) By blocking all client computers from transmitting data
D) By slowing down the data transmission speed for all client computers
B
49
What role does the wireless access point play in the access request technique?
A) It encrypts all data transmissions for security purposes.
B) It connects client computers to the internet.
C) It controls access to the shared wireless medium.
D) It provides physical support for wireless devices.
C
50
How do client computers behave while one computer has permission to transmit data?
A) They continue transmitting data simultaneously.
B) They wait until the currently transmitting computer finishes.
C) They disconnect from the network.
D) They send requests to other client computers for permission to transmit
B
51
Polling is the process of permitting all clients to transmit or receive at any time
F. Polling is the process of sending a signal to a client computer that permits it to transmit.
52
________ is the process of sending a signal to a client that gives its permission to
transmit or asks it to receive.
a. Contention
b. Polling
c. Pooling
d. Carrier sense
e. CRC
B
53
What is polling in a network communication context?
A) Sending data to all clients simultaneously
B) Controlling access to the network through encryption
C) Sending a signal to a client computer permitting it to transmit
D) Filtering incoming data packets for security purposes
C
54
What role do client computers play in polling?
A) They determine the frequency of polling signals.
B) They store data that needs to be transmitted.
C) They control access to the network.
D) They encrypt the data before transmission.
B
55
How does the controlling device in polling interact with client computers?
A) It sends a signal to all clients simultaneously.
B) It randomly selects clients to send data.
C) It periodically checks each client to see if it has data to transmit.
D) It only communicates with the client that has the most data to transmit.
C
56
How does a client computer respond if it has no data to send during polling?
A) It sends a positive acknowledgment to the polling signal.
B) It encrypts the data before transmission.
C) It ignores the polling signal.
D) It responds negatively to the polling signal.
D
57
What is the purpose of the periodic polling of client computers by the controlling device?
A) To restrict access to the network based on location
B) To ensure that all client computers have a chance to transmit data
C) To prioritize certain clients over others based on data needs
D) To maximize network bandwidth for high-priority traffic
B
58
With roll-call polling, a server polls clients in a consecutive, pre-arranged priority list
T
59
Roll call polling cannot be modified to increase priority of clients or terminals
F
60
Roll call polling does not require a server, host, or special device that performs the
polling
F
61
Roll call polling is a type of contention approach to media access control
F
62
Roll call polling typically involves some waiting because the server has to wait for a
response from the polled client or terminal.
T
63
Which of the following is true about roll call polling?
a. It cannot be modified to increase priority of clients or terminals.
b. It does not require a server, host, or special device that performs the polling.
c. It is also called token passing.
d. It is a type of contention approach to media access control.
e. It typically involves some waiting because the server has to wait for a response
from the polled client or terminal.
E
64
Token passing is a term that refers to hub polling, in which one computer starts a poll
and passes it to the next computer on a multipoint circuit.
T
65
What action does a device take after receiving the token in hub polling?
A) It sends a message to all other devices on the network.
B) It transmits data if it has any and then passes the token to the next device.
C) It waits for another device to request permission to transmit.
B
66
How does the hub polling cycle restart?
A) When all devices have transmitted data once
B) When the hub sends a reset signal to all devices
C) When the token reaches the first device that initiated the polling process
D) When a device detects an error in data transmission
C
67
The two categories of network errors are lost data and delimited data
F. Corrupted data and Lost data
68
How are human errors typically controlled in a network system?
a) Through hardware mechanisms
b) Through application programs
c) Through physical controls
d) Through administrative controls
B
69
Which type of error is exemplified by a mistake in typing a number?
a) Hardware error
b) Software error
c) Human error
d) Network error
C
70
What is the primary control mechanism for human errors in network systems?
a) Network hardware
b) Application programs
c) Physical controls
d) Administrative controls
B
71
How are network errors typically controlled?
a) Through physical controls
b) Through application programs
c) Through network hardware and software
d) Through administrative controls
C
72
What is an example of a network error?
a) Software bug
b) Typing mistake in a number
c) Changing a bit value during transmission
d) Power outage
C
73
If a computer transmits a message containing “ABC” and the destination computer
receives “abc” as the message, the message is corrupted.
T
74
What is corrupted data?
a) Data stored in multiple locations
b) Data with redundant information
c) Data that is changed from its original form
d) Data transmitted with encryption
C
75
What is lost data?
a) Data stored in multiple locations
b) Data with redundant information
c) Data that cannot be recovered
d) Data transmitted with encryption
C
76
Which of the following best defines error rate?
a) The probability of a single bit being transmitted correctly
b) The frequency of errors in a given amount of transmitted data
c) The rate at which data is compressed during transmission
d) The duration of time it takes for data to be transmitted
B
77
How is error rate typically measured?
a) In bits per second (bps)
b) In hertz (Hz)
c) In percentage of successful transmissions
d) In terms of errors per unit of transmitted data
D
78
What does an error rate of "1 in 500,000" mean?
a) For every 500,000 bits transmitted, one bit is expected to be in error
b) For every 500,000 bits transmitted, all bits are expected to be in error
c) For every bit transmitted, there is a 500,000% chance of error
d) For every 500,000 errors, one bit is transmitted correctly
A
79
In a _________, more than one data bit is changed by the error-causing condition.
a. burst error
b. data rate shift
c. Trellis-coded modulation
d. uniform distribution
e. amplitude key shift
A
80
What is a burst error?
a) An error that occurs randomly in data transmission
b) An error where many bits are corrupted at the same time
c) An error caused by hardware malfunctions
d) An error that affects only a single bit in the data
B
81
How are burst errors characterized?
a) By having uniformly distributed errors
b) By affecting only one bit at a time
c) By not affecting data integrity
d) By having many corrupted bits occurring together
D
82
Which term describes the distribution pattern of errors in burst errors?
a) Uniform distribution
b) Non-uniform distribution
c) Random distribution
d) Symmetric distribution
B
83
Data transmission errors typically are distributed uniformly in time.
F
84
What is a major cause of errors in data transmission?
a) Software bugs
b) Human errors
c) Line noise and distortion
d) Hardware malfunctions
C
85
Which type of transmission media is more susceptible to noise according to the statement?
a) Optical media
b) Coaxial cable
c) Fiber-optic cable
d) Twisted pair wire
B and D.
86
Undesirable stray electrical voltage can cause data communication errors
T
87
What is a characteristic of electrical media in terms of noise susceptibility?
a) They are less prone to noise than optical media
b) They are equally susceptible to noise as optical media
c) They are more susceptible to noise than optical media
d) They are immune to noise interference
C ( electrical media are twisted pair wire and coaxial cable; optical media is fiber-optic cable)
88
What can introduce noise into communication circuits, according to the statement?
a) Human errors only
b) Equipment and natural disturbances
c) Software bugs
d) Network congestion
B
89
What effect does noise have on communication circuit performance?
a) It improves circuit performance
b) It has no effect on circuit performance
c) It degrades circuit performance
d) It increases the reliability of communication
C
90
How does noise manifest as per the statement?
a) Increased transmission speed
b) Extra bits, missing bits, and flipped bits
c) Reduced data redundancy
d) Enhanced data integrity
B
91
Gaussian noise is a special type of attenuation.
F
92
What is White Noise or Gaussian Noise?
a) A type of error in data transmission
b) The background static on radios and telephones
c) The absence of signal in a communication channel
d) The result of network congestion
B. A is not right because it is source of error
93
What causes White Noise or Gaussian Noise?
a) Thermal agitation of electrons
b) Human errors during data transmission
c) Software bugs in communication protocols
d) Physical damage to communication cables
A
94
What effect does White Noise or Gaussian Noise typically have on communication?
a) It enhances signal clarity
b) It increases the speed of transmission
c) It introduces background static or interference
d) It improves data integrity
C
95
How is White Noise or Gaussian Noise described in terms of its impact on transmission?
a) It is inescapable and always problematic
b) It is inescapable but usually not problematic unless severe
c) It can be easily avoided with proper equipment
d) It only occurs in digital communication systems
B
96
What action can be taken to mitigate the impact of White Noise or Gaussian Noise?
a) Decrease signal strength
b) Increase signal strength
c) Decrease data redundancy
d) Increase data transmission speed
B
97
What is Impulse Noise (Spikes)?
a) Background static on radios
b) Clicks or crackling noise heard on telephones
c) Sudden increases in electrical energy
d) Thermal agitation of electrons
C
98
What is a primary characteristic of Impulse Noise?
a) It is predictable
b) It is easy to determine the cause
c) It is challenging to determine the cause
d) It has a constant amplitude
C
99
What effect can Impulse Noise have on data transmission?
a) It enhances signal clarity
b) It improves data integrity
c) It can obliterate a group of bits, causing a burst error
d) It decreases data transmission speed
C
100
What are some examples of sudden increases in electrical energy that can cause Impulse Noise?
a) Earthquakes and hurricanes
b) Software bugs and glitches
c) Voltage changes in adjacent lines and lightning flashes
d) Human errors during data transmission
C
101
How is Impulse Noise different from White Noise or Gaussian Noise?
a) It is predictable
b) It is caused by movement of electrons
c) It is more challenging to determine the cause
d) It is not inescapable
C
102
How can Impulse Noise be prevented or fixed, according to the provided information?
a) Increase the data transmission speed
b) Shield or move the wires
c) Decrease the signal strength
d) Increase the data redundancy
B
103
The thermal agitation of electrons causes impulse noise.
F
104
Which type of noise is more likely to cause burst errors due to its sudden increase in electrical energy?
a) Gaussian Noise
b) White Noise
c) Impulse Noise
d) Thermal Noise
C
105
What is cross-talk?
a) Background noise on communication devices
b) Interference caused by wet weather conditions
c) When one circuit picks up signals from another
d) Random fluctuations in signal strength
C
106
Crosstalk occurs when the signal transmitted on one circuit or channel of a
transmission system creates an undesired effect in another circuit or channel
T
107
In which scenario does cross-talk commonly occur?
a) When signals are transmitted with high amplitudes
b) When wires are physically too far apart
c) When multiple signals are transmitted through multiplexed links
d) When the weather is dry and clear
C
108
What is an example of cross-talk happening?
a) Radio stations broadcasting on different frequencies
b) Microwave links picking up reflections from antennas
c) Network congestion during peak hours
d) One antenna picking up a minute reflection from another antenna
B
109
What can result from multiplexer guardbands being too small or wires being too close together?
a) Increased signal strength
b) Decreased signal amplitude
c) Reduced cross-talk
d) One circuit picking up signals from another
D. cross-talk
110
The familiar background static on radios and telephones is called:
a. echoes
b. intermodulation noise
c. gray noise
d. cross-talk
e. white noise
E
111
Another term for impulse noise is:
a. Gaussian noise
b. spikes
c. attenuation
d. cross-talk
e. intermodulation noise
B
112
The primary source of error in data communications is:
a. echoes.
b. intermodulation noise.
c. spikes.
d. attenuation.
e. cross-talk.
C
113
__________can obliterate a group of bits, causing a burst error.
a. Cross-talk
b. Attenuation
c. Impulse noise
d. Intermodulation noise
e. Gray noise
C
114
Cross-talk:
a. occurs when one circuit picks up signals in another.
b. is always bothersome because it has a high signal strength.
c. decreases with increased proximity of two wires.
d. decreases during wet or damp weather.
e. increases with lower frequency signals
A
115
Which of the following is way to reduce or eliminate crosstalk on a circuit?
a. Physically separating the cables from other communication cables
b. Adding repeaters or amplifiers to a circuit
c. Reducing the length of the cable
d. Adding fluorescent lights
e. Shorting a circuit
A
116
When does cross-talk typically worsen?
a) When the wires are far apart
b) When the wires are close together
c) When the signals are strong
d) When the signals have higher frequencies
e) During wet or damp weather conditions
f) All
F
117
What is a recommended method to prevent or fix cross-talk on a circuit?
a) Decrease the guardbands
b) Increase the signal strength
c) Move or shield the wires
d) Reduce the frequency of transmitted signals
C
118
How can the impact of cross-talk be reduced or eliminated?
a) By decreasing the distance between wires
b) By increasing the strength of transmitted signals
c) By increasing the guardbands
d) By decreasing the frequency of transmitted signals
C
119
How can cross-talk issues be addressed effectively?
a) By decreasing the number of signals transmitted
b) By increasing the distance between signals
c) By changing multiplexing techniques
d) By decreasing the guardbands between signals
C
120
When a signal is reflected back to the transmitting equipment, it is called a(n)
_________.
a. white noise
b. echo
c. crosstalk
d. attenuation
e. impulse noise
B. When the reflected signal reaches the transmitting equipment, it interferes with the original signal, causing a repeated sound or data transmission.
121
What is attenuation?
a) Sudden increase in signal strength over distance
b) Gradual decrease in signal strength over distance
c) Complete loss of signal strength over distance
d) Fluctuation in signal strength over distance
B
122
How can attenuation be prevented or fixed?
a) By increasing the distance between devices
b) By using repeaters or amplifiers in the circuit
c) By decreasing the signal frequency
d) By reducing the number of devices in the circuit
B
123
Attenuation refers to the loss of signal strength.
T
124
The loss of power a signal suffers as it travels from the transmitting computer to a receiving
computer is:
a. white noise
b. spiking
c. attenuation
d. intermodulation noise
e. echo
C
125
When the output signal from an amplifier on a circuit is different from the input signal, this is
called _________________.
a. intermodulation noise
b. attenuation
c. echo
d. white noise
e. cross-talk
E
126
_____________ is an effective way to prevent attenuation.
a. Shielding wires
b. Adding fluorescent lights
c. Adding repeaters or amplifiers to a circuit
d. Changing multiplexing techniques
e. Shorting a circuit
C
127
When the signals from two circuits combine to form a new signal that falls into a
frequency band reserved for another signal, this is called intermodulation noise.
T
128
If a signal with a frequency of 500 MHz combines with another signal of 1500 MHz
and they form a new signal of 2000 MHz, this is an example of:
a. intermodulation noise
b. attenuation
c. echo
d. white noise
e. cross-talk
A
129
What is intermodulation in the context of signal transmission?
a) A special type of attenuation
b) A type of signal reflection
c) A special type of cross-talk
d) Signals combining to form new frequencies
C
130
What can cause intermodulation noise in a modem?
a) Weak signal transmission
b) Maladjusted equipment transmitting strong frequency tones
c) Perfect alignment of equipment
d) Absence of signal transmission
B
131
Which scenario describes an example of intermodulation noise?
a) A modem transmitting data without any issues
b) Signals on a multiplexed line being amplified together
c) Signals being transmitted at different frequencies with no interaction
d) Signals being transmitted with perfect alignment
B
132
_____________ is an effective way to prevent impulse noise, cross talk, and
intermodulation noise.
a. Shielding wires
b. Adding fluorescent lights
c. Adding repeaters to a circuit
d. Adding amplifiers to a circuit
e. Shorting a circuit
A
133
In which type of transmission are errors more likely to occur compared to cable transmission?
a) Wireless transmission
b) Microwave transmission
c) Satellite transmission
d) All of the above
D
134
Which transmission medium is generally considered more reliable in terms of error occurrence?
a) Wireless transmission
b) Microwave transmission
c) Satellite transmission
d) Cable transmission
D
135
Shielding cables
covering them with an insulating coating
136
disadvantage of shielding cables
more shielding more expensive and hard to install
137
Moving cables from sources of noise
+ Away from other cables
+ Away from power source
138
_____________ is an effective way to prevent impulse noise, cross talk, and intermodulation
noise.
a. Shielding wires
b. Adding fluorescent lights
c. Adding repeaters to a circuit
d. Adding amplifiers to a circuit
e. Shorting a circuit
A
139
_____________ is an effective way to prevent attenuation.
a. Shielding wires
b. Adding fluorescent lights
c. Adding repeaters or amplifiers to a circuit
d. Changing multiplexing techniques
e. Shorting a circuit
C
140
Which of the following issues can result from improper multiplexing?
a) Signal amplification
b) Cross-talk and intermodulation noise
c) Decreased bandwidth usage
d) Enhanced signal clarity
B
141
What technique can help mitigate cross-talk and intermodulation noise in multiplexing?
a) Increasing the signal power
b) Switching from TDM to FDM
c) Adjusting frequencies or guardbands
d) Adding more channels without adjustments
B
142
What technique can help mitigate cross-talk and intermodulation noise in multiplexing?
a) Increasing the signal power
b) Switching from TDM to FDM
c) Adjusting frequencies or guardbands
d) Adding more channels without adjustments
B
143
In FDM, what are guardbands primarily used for?
a) Boosting signal strength
b) Preventing signal distortion
c) Enhancing channel capacity
d) Eliminating multiplexing errors
B
144
What advantage does Time Division Multiplexing (TDM) offer over Frequency Division Multiplexing (FDM) in terms of mitigating interference?
a) TDM allows for wider guardbands
b) TDM reduces the likelihood of cross-talk
c) TDM enables higher frequency allocations
d) TDM eliminates the need for guardbands entirely.
B. Changing multiplexing techniques (e.g., from FDM to TDM) or adjusting frequencies or guardbands in FDM can help mitigate these issues. ( cross talk and intermodulation)
145
What types of noise can result from poorly maintained equipment or connections?
a) Echoes and reverberation
b) White noise and echoes
c) Harmonics and distortion
d) Phase shifts and attenuation
B.
146
How can echoes and white noise stemming from equipment maintenance issues be mitigated?
a) Increasing signal power
b) Implementing noise cancellation algorithms
c) Tuning transmission equipment
d) Adding more cables for redundancy
C
147
Which aspect of equipment maintenance directly addresses issues related to connections and splices among cables?
a) Signal modulation
b) Frequency allocation
c) Power distribution
d) Ensuring proper connections and splices
D
148
What is the primary function of an amplifier in a communication system?
a) Decreasing the strength of the incoming signal
b) Amplifying the strength of the incoming signal
c) Filtering out noise from the incoming signal
d) Storing the incoming signal for later transmission
B
149
What effect does amplification have on both the signal and the noise?
a) Only increases the signal strength
b) Only increases the noise strength
c) Increases the strength of both the signal and the noise
d) Decreases the strength of both the signal and the noise
C
150
What does an amplifier do after receiving and amplifying the signal and noise?
a) Filters out the noise before retransmission
b) Reduces the strength of the signal before retransmission
c) Retransmits the amplified signal and noise as received
d) Stores the signal and noise for future use
C
151
The distance between repeaters or amplifiers on a telephone circuit is determined by
the amount of power gained per unit length of the transmission.
F. The distance between these devices depends on how much signal strength is lost over each part of the line. Usually, they're spaced every 1 to 10 miles
152
When we amplify the signal on an analog circuit, we also amplify any noise that is
present on the circuit
T
153
Which of the following is way to reduce or eliminate crosstalk on a circuit?
a. Physically separating the cables from other communication cables
b. Adding repeaters or amplifiers to a circuit
c. Reducing the length of the cable
d. Adding fluorescent lights
e. Shorting a circuit
A
154
On digital circuits, we use _________ to reshape the incoming signal and prevent attenuation.
a. amplifiers
b. repeaters
c. multiplexers
d. digitizers
e. modems
B
155
What is the primary function of a repeater in digital circuits?
a) Decreasing the signal strength
b) Translating the incoming signal into a digital message
c) Filtering out noise from the incoming signal
d) Storing the incoming signal for later transmission
B
156
How does a repeater handle noise and distortion from the previous circuit?
a) Amplifies noise and distortion
b) Filters out noise and distortion
c) Ignores noise and distortion
d) Recreates the message, avoiding amplification of noise and distortion
D
157
What is the result of using repeaters in digital circuits in terms of signal quality?
a) Increased noise and distortion
b) Improved signal clarity
c) Reduction in signal strength
d) Introduction of more errors
B
158
Why does using repeaters result in a lower error rate for digital circuits?
a) Because repeaters eliminate the need for digital encoding
b) Because repeaters amplify noise and distortion
c) Because repeaters recreate the message, avoiding amplification of noise and distortion
d) Because repeaters decrease the efficiency of digital transmission
C
159
Which of the following is way to reduce or eliminate crosstalk on a circuit,
a. changing multiplexing techniques
b. adding repeaters or amplifiers to a circuit
c. reducing the length of the cable
d. adding fluorescent lights
e. shorting a circuit
A
160
For effective error detection and correction, extra error detection “data” must be
included with each message
T
161
Which layer of the OSI model is responsible for adding error-detection data to each message?
a) Network layer
b) Transport layer
c) Data link layer
d) Physical layer
C
162
In error detection, what does the receiver do to determine if an error has occurred?
a) Ignores the received message
b) Matches the received message against the transmitted error-detection data
c) Discards the received message immediately
d) Increases the throughput of useful data
B
163
How does increasing the amount of error-detection data affect error-detection performance?
a) It decreases error detection accuracy
b) It has no impact on error detection
c) It enhances error-detection performance
C. but reduces the throughput of useful data
164
What is the relationship between the efficiency of data throughput and the desired amount of error detection?
a) They are directly proportional
b) They are inversely proportional
c) They are independent of each other
d) They vary randomly with each transmission.
B
165
What is the relationship between the efficiency of data throughput and the desired amount of error detection?
a) They are directly proportional
b) They are inversely proportional
c) They are independent of each other
d) They vary randomly with each transmission.
B
166
In an odd parity-checking scheme, the parity bit is set to make the total number of ones in the
byte (including the parity bit) an even number.
F
167
Parity checking can only detect an error when an even number of bits are switched.
F. Parity can only detect errors when an odd number of bits have been switched; any even number of errors cancel each other out.
168
Which error detection technique involves adding an extra bit to a binary code to ensure the total number of ones is even or odd?
a) Parity checking
b) Checksum
c) Cyclic Redundancy Check (CRC code)
A
169
Using parity, the probability for detecting an error, given that one has occurred, is
about 50% for either even or odd parity
T
170
Using parity, the probability for detecting an error, given that one has occurred, is
about 25% for either even or odd parity.
F
171
Using parity, the probability for detecting an error, given that one has occurred, is
about 70% for even parity and 30% for odd parity.
F
172
Using parity, the probability for detecting an error, given that one has occurred, is
about 30% for even parity and 70% for odd parity.
F
173
Using parity, the probability for detecting an error, given that one has occurred, is
about 20% for either even or odd parity
F
174
Using parity, the probability for detecting an error, given that one has occurred, is
about 100% for either even or odd parity.
F
175
With odd parity (assume that the parity bit (in bold) has been placed at the end of
each of the following) and a 7-bit ASCII code, which of the following is incorrect?
a. 01101011
b. 00011011
c. 00100101
d. 10110110
e. 11111110
B
176
The probability of detecting an error, given that one has occurred, using parity
checking is about:
a. 0%
b. 50%
c. 75%
d. 98%
e. 100%
B
177
Using parity, the probability for detecting an error, given that one has occurred, is:
a. about 50% for either even or odd parity.
b. about 70% for even parity and 30% for odd parity.
c. about 30% for even parity and 70% for odd parity.
d. about 0% for either even or odd parity.
e. about 100% for either even or odd parity.
A
178
Which of the following is not an error detection method used in the data link layer?
a. parity checking
b. cyclic redundancy checking
c. CRC-32
d. pulse code checking
e. odd parity
D
179
How is the checksum calculated by the sender in the checksum error detection technique?
a) Adding binary values of each character in the message
b) Adding decimal values of each character in the message and dividing by 255
c) Subtracting the values of each character in the message
d) Multiplying the values of each character in the message
B
180
What does the sender do with the remainder obtained after dividing the total by 255 in checksum calculation?
a) Discards it
b) Uses it as the checksum
c) Adds it to the end of the message
d) Sends it separately
B
181
How is the checksum typically included in the message by the sender?
a) Prepends it to the beginning of the message
b) Inserts it randomly within the message
c) Appends it to the end of the message
d) Encrypts it within the message content
C
182
Approximately what percentage of errors can the checksum error detection method detect?
a) 50%
b) 75%
c) 95%
d) 100%
C
183
Which of the following accurately describes the size of the checksum typically used in the checksum error detection method?
a) 4 bytes
b) 8 bytes
c) 1 byte
d) 2 bytes
C
184
Cyclical redundancy check is one of the most popular polynomial error-checking
schemes
T
185
The probability of detecting an error, provided that one has occurred, using cyclic
redundancy checking is about:
a. 0%
b. 75%
c. 50%
d. > 99%
e. exactly 100%
D
186
In CRC (Cyclic Redundancy Check), what does 'P' represent in the division formula P/G = Q + R/G?
a) The quotient
b) The message (treated as one long binary number)
c) The remainder
d) The fixed number determining the length of R
B
187
What does 'G' represent in the CRC division formula P/G = Q + R/G?
a) The remainder
b) The quotient
c) A fixed number determining the length of R
d) The message (treated as one long binary number)
C
188
What is the role of 'Q' in the CRC division formula P/G = Q + R/G?
a) The remainder
b) The message (treated as one long binary number)
c) The fixed number determining the length of R
d) The quotient (whole number)
D
189
How is the remainder 'R' utilized in CRC error detection?
a) It is discarded.
b) It is used to reconstruct the message.
c) It is added to the message as error-detection data.
d) It is used to calculate the quotient.
C
190
Which statement accurately describes the length of 'R' in CRC error detection?
a) 'R' could be of variable length.
b) 'R' is always 8 bits long.
c) 'R' is always 32 bits long.
d) 'R' is determined by the length of the message.
A
191
The simplest method for error correction is retransmission.
T
192
Another term for stop-and-wait ARQ is sliding window.
F. continuous window
193
ARQ means that:
a. a receiver that detects an error in a message simply asks the sender to retransmit the
message until it is received without error
b. the common carrier Automatically Returns Queries to the subscriber upon receipt of
such queries
c. a sender is using a data link protocol called Asynchronous Repeating reQuest
d. a fiber optic cable meets the American Registered Quality, a certification standard for
use in high-quality data communication transmission lines
e. a sender is using a parity scheme called Array Resource Quality
A
194
In ARQ, a NAK:
a. is sent by the recipient if the message was received without error
b. is sent by the sender at the same time as it sends a data packet
c. is sent by the recipient if the message contains an error
d. refers to non-asynchronous Kermit technique
e. means that the sender should continue with sending the next message
C
195
One type of forward error correction is the Hamming code.
T
196
Forward error correction is commonly used in satellite transmission
T
197
______________ controls errors by detecting and correcting them at the receiving end
without retransmission of the original message.
a. Hamming code
b. Huffman encoding
c. Front end processing
d. Wave division
A
198
What is the primary advantage of Forward Error Correction (FEC)?
a) Reducing transmission times
b) Eliminating the need for retransmission
c) Increasing the speed of data transfer
d) Decreasing the amount of transmitted data
B
199
What additional information is required for Forward Error Correction (FEC)?
a) Signal strength data
b) Timing synchronization data
c) Corrective information
d) Packet sequence numbers
C
200
How is the corrective information in FEC sent along with the message?
a) Appended to the end of the message
b) Encrypted within the message content
c) Sent in a separate data packet
d) Embedded within the message header
A
201
What does Forward Error Correction (FEC) allow the receiver to do?
a) Retransmit the original message
b) Ignore errors in the incoming message
c) Check and correct errors in the incoming message
d) Encrypt the incoming message
C
202
What characteristic defines the amount of extra information required for FEC?
a) Always 50% of the message size
b) Depends on the transmission medium
c) Can be up to 100% of the message size
d) Is fixed and predetermined for all transmissions
C
