Business Data Communications and Networking 7th Edition Test Bank - Chapter 03

Business Data Communications and Networking 7th Edition Test Bank - Chapter 01 (400 Level Course)

TRUE/FALSE

The following are possible True/False questions for tests. The statement is given and the answer is provided in square brackets. The level of difficulty (easy, moderate, difficult) and the page(s) relevant to the question are also furnished.

1. The word circuit can refer either to the physical circuit or to the logical circuit. [True; p. 70-71]
Easy

2. Computers produce digital data whose values are binary: 0 or 1. [True; p. 71]
Easy

3. Analog data can take on any value in a wide range of possibilities. [True; p. 71]
Easy

4. Networks designed for primarily for digital (computer) data tend to use digital transmission. [True; p. 71]
Easy

5. Digital data can be converted to analog signals by using a special device called a modem. [True; p. 71]
Easy

6. Newer telephone circuits, built during the last decade, offer higher quality because they were built using analog transmission. [False, they use digital transmission; p. 71]
Easy

7. In a multipoint circuit configuration, each computer has a dedicated circuit between itself and each of the other computers in the network. [False, many computers are connected on the same circuit; p. 72]
Easy

8. In simplex transmission, the data flows in both directions at the same time. [False, it can flow in only one direction; p. 73]
Easy

9. The amount of time it takes to switch between sending and receiving in half-duplex transmission is called the propagation delay. [False, it is the turnaround time; p. 73]
Moderate

10. The medium is the physical matter or substance that carries the voice or data transmission. [True; p. 74]
Easy

11. Guided media refers to the type of media in which the message is broadcast through the air. [False; it is the media in which data flows through a physical substance such as fiber optics; p. 74]
Easy

12. For wide area networks, circuits may be provided by various common carriers, such as Sprint. [True; p. 74]
Moderate

13. In twisted pair wires, the ‘twisting’ minimizes the electromagnetic interference. [True; p. 74]
Moderate

14. One advantage of coaxial cable over low cost twisted pair wires is that coax cables are less susceptible to interference. [True; p. 75]
Easy

15. Fiber optic cable carries signals in traditional electrical form. [False, they use light pulses to transmit; p. 75-76]
Easy

16. The earliest type of fiber optic systems was single mode. [False, they were multimode; p. 76]
Easy

17. One of the least commonly used forms of wireless media is radio. [False, it is very common; p. 77]
Easy

18. Microwave uses low frequency light waves to carry the data in a direct line-of-sight path. [False, it is a very high frequency radio communication; p. 78]
Easy

19. Congestion in large cities is not an issue with microwave transmission. [False, it is a problem; p. 79]
Easy

20. Except for transmission distance, satellite transmission is similar to transmission via microwave. [True; p. 79]
Moderate

21. One form of interference with satellite transmission is called raindrop attenuation in which the transmissions are absorbed by heavy rain. [True; p. 80]
Easy

22. One important factor in choosing media for a network is security. [True; p.81]
Easy

23. Coding schemes are groups of bits that translate into the “alphabet” of any given system. [True; p. 82]
Easy

24. ASCII is the least popular code for data communications. [False, it is the most popular code used today; p. 82]
Easy

25. The predominant method of transferring information internally in a computer is via parallel mode. [True; p. 83]
Moderate

26. Non-return-to-zero is a type of unipolar signaling. [False; it is a type of bipolar signaling; p. 84]
Moderate

27. Ethernet, a common LAN technology, uses Manchester encoding. [True; p. 85]
Easy

28. POTS refers to plain old telephone system. [True; p. 86]
Easy

29. Amplitude of an analog signal is the same as loudness. [True; p. 86]
Easy

30. Modulation refers to “shape changes” of the sound waves to represent 0’s or 1’s. [True; p. 87]
Moderate

31. Four different amplitude possibilities are required to transmit two bits per wave using amplitude modulation. [True; p. 88]
Moderate

32. Although it is theoretically possible to send an infinite number of bits per wave using one-type (not combined, as in QAM) modulation, it becomes difficult to distinguish among all the possibilities. [True; p. 88-89]
Moderate

33. According to the ITU-T, baud rate is the same as symbol rate. [True; p. 89]
Moderate

34. Data compression increases the throughput of a communication link. [True; p. 91]
Easy

35. Analog data must be translated into a series of binary bits before transmission over a digital communication medium. [True; p. 92]
Moderate

MULTIPLE CHOICE

The following are possible multiple-choice questions for tests. The question is posed and the answer is provided under the choices. The level of difficulty (easy, moderate, difficult) and the page(s) relevant to the topic are also furnished.

1. Data is physically transmitted from one computer or terminal to another in the ________ layer.
a. physical
b. transport
c. application
d. terminal
e. data link
Answer: a, Easy, p. 70

2. Two fundamentally different types of data are:
a. DSL and ADSL
b. asymmetric and symmetric
c. Microsoft and IBM
d. digital and analog
e. local area and wide area
Answer: d, Easy, p. 71

3. In general, networks designed to transmit primarily computer data are likely to be ________, while networks designed to transmit voice data are likely to be ________.
a. slow, fast
b. level 1, level 2
c. numeric, musical
d. direct, indirect
e. digital, analog
Answer: e, Easy, p. 71

4. Analog data can be transmitted over a digital network by using a special device called a:
a. digitizer
b. analog converter
c. protocol converter
d. modem
e. codec
Answer: e, Easy, p. 71

5. Which of the following is not a key advantage of digital transmission?
a. It permits only low transmission rates.
b. It is more efficient.
c. It is simpler to integrate voice, video, and data on the same circuit.
d. It is more secure.
e. It produces fewer errors.
Answer: a, Moderate, p. 71

6. In the future, most long distance transmission (voice, data, and video) will be sent using:
a. analog transmission
b. digital transmission
c. unipolar signaling
d. analog transmission
e. infrared linking
Answer: b, Moderate, p. 72

7. A(n) __________ circuit is another name for a multipoint configuration.
a. analog
b. dedicated
c. point-to-point
d. shared
e. simplexed
Answer: d, Moderate, p. 72

8. The two basic types of media are:
a. statistical and frequency
b. guided and wireless (radiated)
c. local and wide area
d. attenuator and Gaussian
e. duplexed and non-duplexed
Answer: b, Easy, p. 74

9. Which of the following would be considered a type of wireless media?
a. unshielded twisted pair
b. shielded twisted pair
c. coaxial cable
d. microwave
e. fiber optics
Answer: d, Moderate, p. 74

10. The earliest type of fiber optic systems were:
a. Graded index multimode
b. Attenuated
c. Multimode
d. Single mode
e. Step mode
Answer: c, Easy, p. 76

11. Another term for the weakening of a signal over distance is:
a. turnaround time
b. propagation delay
c. dispersion
d. insulation
e. attenuation
Answer: e, Difficult, p. 76

12. Which of the following media can best withstand harsh environmental conditions?
a. shielded twisted pair
b. unshielded twisted pair
c. Cat 5 twisted pair
d. coaxial cable
e. fiber optic cable
Answer: e, Moderate, p. 77

13. __________ is a line-of-sight type of wireless media.
a. coaxial cable
b. microwave
c. radio
d. twisted pair
e. fiber optic
Answer: b, Moderate, p. 77-79

14. Microwave transmission:
a. is a type of high frequency radio communication
b. requires a clear line-of-sight path
c. is typically used for long distance data transmission
d. does not require the laying of any cable
e. all of the above
Answer: e, Easy, p. 78

15. ______________ refers to the time it takes for a signal to travel from sender to recipient (highly exaggerated with satellite transmission).
a. Line-of-sight effect
b. Multimode index
c. Saturation effect
d. Raindrop attenuation
e. Propagation delay
Answer: e, Easy, p. 79

16. Which of the following is not an important factor to consider when selecting media to be used in a network?
a. prestige value of the type of media
b. type of network
c. cost
d. transmission distance
e. security
Answer: a, Moderate, p. 81-82

17. Which of the following media is the least secure?
a. coaxial cable
b. unshielded twisted pair
c. shielded twisted pair
d. fiber optic cable
e. infrared
Answer: e, Easy, p. 81

18. Transmission speeds:
a. are the same among all media
b. are not a factor in selecting a media because all media have more than enough speed to serve current communication demands
c. are a constant, 56Kbps, for all media types
d. differ widely among media
e. always have a direct correlation with security
Answer: d, Moderate, p. 81

19. Which of the following is a byte, under the normal definition?
a. 1
b. a special character that is used for Apple computers only
c. 0
d. 325
e. 8 consecutive bits, such as 00011100, that represent one unit or character
Answer: e, Moderate, p. 82

20. ____________ is one of the most commonly used coding schemes used in data transmission.
a. ASCII
b. ISDN
c. MAU
d. ATM
e. FDM
Answers: a, Moderate, p. 82

21. Under one type of ASCII, each character is represented by 7 bits. That means that there are ________ valid combinations that can represent different characters.
a. 23
b. 256
c. 128
d. 1092
e. 8
Answers: c, Moderate, p. 82

22. The representation of the character A by the group of 8 bits, 10000001, is an example of:
a. digital coding
b. phase modulation
c. binary modulation
d. analog transmission
e. pitch variation
Answers: a, Moderate, p. 82

23. When all bits of a character are transferred one after another, the bits are transferred in ___________ mode.
a. serial
b. frequency division
c. multiplexing
d. parallel
e. full complex
Answers: a, Moderate, p. 83

24. Which of the following statements is correct?
a. Parallel transmission is most often used for sending data on a circuit that is made up of one wire.
b. Parallel transmission is distinguished from serial transmission by the fact that the transmitting device sends a single bit, then a second bit, and so on, until all the bits are transmitted.
c. Parallel transmission is only used for analog data.
d. Serial transmission is considerably slower than parallel transmission.
e. Parallel transmission is the same as serial transmission.
Answers: d, Moderate, p. 83

25. ___________ is not a type of digital signaling technique.
a. Non-return-to-zero signaling
b. Unipolar signaling
c. Manchester encoding
d. Return-to-zero signaling
e. Data rate signaling
Answer: e, Moderate, p. 84

26. With which type of digital signaling does the signal always return to zero volts after each bit?
a. Non-return-to-zero signaling
b. Unipolar signaling
c. Return-to-zero signaling
d. Data rate signaling
e. Huffman encoding signal
Answer: c, Easy, p. 84

27. Which type of digital signaling would experience fewer errors because it has more distinct signals?
a. unipolar
b. serial
c. double current
d. attenuation
e. Huffman encoding signal
Answer: c, Difficult, p. 84

28. Which of the following is a characteristic of sound waves that can be modulated to convert digital data into analog signals?
a. phase
b. attenuation
c. bipolar
d. bandwidth
e. codec
Answer: a, Moderate, p. 86

29. The direction in which the sound wave begins is known as:
a. amplitude, which our ears detect as loudness
b. frequency, which our ears detect as pitch
c. phase
d. bandwidth
e. furlong
Answer: c, Moderate, p. 86

30. The height of a sound wave is called its:
a. frequency
b. phase
c. amplitude
d. bandwidth
e. furlong
Answer: c, Moderate, p. 86

31. _____________ is not a form of modulation used to transform digital data into analog signals.
a. synchronous time division
b. amplitude shift keying
c. amplitude modulation
d. frequency modulation
e. phase modulation
Answer: a, Moderate, p. 87

32. With respect to converting digital data into analog signals, AM stands for:
a. Asynchronous Manchester
b. Analog Multimode
c. Amplitude Modulation
d. Anomaly Multiplexing
e. Analytical Mosaic
Answer: c, Moderate, p. 87

33. In which type of modulation is a 1 distinguished from a 0 by shifting the direction in which the wave begins?
a. bandwidth modulation
b. amplitude modulation
c. frequency modulation
d. phase modulation
e. codec modulation
Answers: d, Moderate, p. 87

34. When sending four bits at a time using frequency modulation, the number of different frequency levels that would be needed would be _______.
a. 24
b. 16
c. 2
d. 8
e. 4
Answer: b, Moderate, p. 88

35. ____________ is a modulation technique that combines two different amplitude combinations with eight different phase combinations modulation to send four bits per wave, or symbol.
a. quadrature amplitude modulation
b. time division multiplexing
c. synchronous digital line control
d. pulse code modulation
e. baseband signaling
Answer: a, Moderate, p. 89

36. TCM stands for:
a. Tandem Control Microprocessor, a hardware feature of front end processors used to manage and control data communications
b. Telephone Call Manager, a software package to monitor and report on telephone usage
c. Trellis coded modulation, a technique that combines phase modulation and amplitude modulation
d. Threaded Code Messaging, a data communications transmission technique in which all redundant bits are stripped before sending and replaced upon receipt of the message
e. True Calling Measures, one telephone company’s method for changing customers
Answers: c, Moderate, p. 89

37. __________ is a unit of signaling speed that indicates how often the signal changes on a communication circuit.
a. bits per second rate
b. phase rate
c. symbol rate
d. attenuation rate
e. trellis rate
Answer: c, Moderate, p. 89

38. The _____________ of a circuit determines a circuit’s capacity.
a. frequency
b. bandwidth
c. phase
d. amplitude
e. loudness
Answer: b, Moderate, p. 89

39. The typical range of human hearing is:
a. 0 to 4,000 Hz
b. 0 to 1,200 Hz
c. 20 to 14,000 Hz
d. 0 to 300 Hz
e. 0 to 56,000 Hz
Answer: c, Easy, p. 89

40. __________ is the approximate bandwidth of traditional telephone circuits.
a. 30,000 - 40,000 Hz
b. 300 - 400 Hz
c. 3 - 4 Hz
d. 3000 - 4000 Hz
e. 9000 – 10000 Hz
Answer: d, Moderate, p. 90

41. To get more “bandwidth” in a digital transmission, you must:
a. increase the range of frequencies available for a transmission
b. increase the loudness per transmission
c. decrease the bits per second transmission speed
d. increase the phase shifts per transmission
e. increase the baud rate per transmission
Answer: a, Moderate, p. 90

42. Which of the following statements is true?
a. the longer the distance of a telephone wire between sender and recipient, the lower the bandwidth across that wire
b. the shorter the distance of a telephone wire between sender and recipient, the lower the bandwidth across that wire
c. bandwidth is constant across any wire, therefore distance is not relevant
d. the longer the distance of a telephone wire between sender and recipient, the higher the bandwidth across that wire
e. bandwidth is not a term that can be used when discussing telephone transmissions
Answer: a, Difficult, p. 90

43. Using TCM that sends 6 bits per each signal and a voice grade line with a bandwidth of 3000 Hz (assume: no noise on the line), the data capacity would be ___________ bits per second.
a. 56K
b. 6
c. 24,000
d. 500
e. 18,000
Answer: e, Moderate, p. 90

44. The acronym, Modem, stands for _________________.
a. multiplexing/demultiplexing
b. more/demote
c. Mode-M technique
d. modulator/demodulator
e. Mod emulation technique
Answer: d, Easy, p. 90

45. Which statement is false about modems?
a. modems are usually used in pairs (2 at a time)
b. a receiving modem demodulates and a sending modem modulates
c. most modems support several modem standards so that they can communicate with a variety of modems
d. modems may operate at a lower speed that that for which they are rated, especially if they detect noise in the communication line
e. modems must always be internal to the computer
Answer: e, Moderate, p. 90-91

46. ______ is a modem standard that uses Lempel-Ziv encoding to compress data.
a. V.22
b. V.44
c. V.32bis
d. V.34
e. RS 232
Answer: b, Moderate, p. 91

47. When V.34 modems initially connect, they must go through a ____________ sequence to test the circuit and determine the optimum combination of symbol rate and modulation technique that will produce the highest throughput.
a. frequency division
b. wave division
c. handshaking
d. Trellis-coded modulation
e. point of presence
Answer: c, Easy, p. 91

48. Codec refers to:
a. codependent decreasing compression
b. co- Digital Equipment Corporation
c. Codd’s laws for data relations
d. code/decode
e. continuous operational digital energy communication
Answer: d, Moderate, p. 92

49. _____________ refers to the difference between the original analog data and the approximation of that data using the techniques for translating from analog data to digital signals.
a. quantizing error
b. handshaking phase
c. modulating frequency
d. POTS anomaly
e. amplitude Trellis effect
Answer: a, Moderate, p. 92

50. When converting analog voice data to digital signals, Pulse Code Modulation samples the incoming voice signal _______ times per second.
a. 8,000
b. 8
c. 18,000
d. 64
e. 256
Answer: a, Moderate, p. 94

51. A 56K modem that uses the V.90 standard:
a. never has problems with noise on the telephone line
b. can recognize an 8-bit digital symbol 8000 times per second
c. transmits 56,000 different symbol changes per second at all times
d. can be used at full capacity on all North American telephone lines
e. currently has 56K transmission rates in both upstream and downstream channels
Answer: b, Moderate, p. 95

52. A(n) ___________ divides one high-speed communication circuit into several lower speed circuits for the primary reason of saving communication line costs.
a. transponder
b. multiplexer
c. inverse multiplexer
d. codec
e. intelligent terminal
Answer: b, Moderate, p. 95

53. The type of multiplexer that divides the circuit horizontally into different light frequencies that are transmitted simultaneously across many channels is a:
a. wave division multiplexer
b. time division multiplexer
c. statistical time division multiplexer
d. frequency division multiplexer
e. statistical frequency division multiplexer
Answer: a, Moderate, p. 96

54. Frequency division multiplexing:
a. operates by statistically time slicing the signal
b. operates by dividing the signal into different frequencies
c. uses a codec that divides signals into different channels
d. operates by time slicing the signal
e. operates by light dividing the signal
Answer: b, Easy, p. 96

55. ________________ separate channels to reduce interference between channels in frequency division multiplexing.
a. Channel blockers
b. Statistical dividers
c. Attenuators
d. Guardbands
e. Adaptive differential processors
Answer: d, Moderate, p. 96

56. Which of the following types of multiplexing is least efficient for data transmission?
a. frequency division multiplexing
b. statistical time division multiplexing
c. statistical frequency division multiplexing
d. time division multiplexing
e. wave division multiplexing
Answer: a, Moderate, p. 96-98

57. Time (non-statistical) division multiplexing differs from frequency division multiplexing because it:
a. does not share a communication circuit
b. splits the communication circuit vertically (with time slots) instead of horizontally
c. increases the wavelength and phase angles of the baseband frequency used for transmission
d. moves the baseband of a circuit by shifting it to a higher frequency
e. reduces baseband signal velocity more than frequency division multiplexing
Answer: b, Moderate, p. 97

58. Statistical time division multiplexers differ from time division multiplexers because they:
a. can cause time delays when all devices are being used for data transmission at the same time
b. take idle time of terminals into account to increase circuit throughput
c. use a complicated statistical formula to allocate time slots
d. all of the above
e. none of the above
Answer: d, Difficult, p. 97-98

59. Inverse multiplexing means:
a. combining several low speed circuits to enable them to be transmitted across one high speed circuit
b. multiplexing from the terminal to the host, rather than from the host to the terminal
c. combining high speed circuits to enable them to be transmitted across one low speed circuit
d. inverting the frequencies used for transmission across a low speed circuit for switching to a digital circuit
e. multiplexing to a codec, rather than to a modem
Answer: a, Moderate, p. 100

60. Digital Subscriber Line:
a. is a fairly recent approach to provide higher data transmission rates across traditional voice circuits in the local loop
b. combines analog transmission and frequency division multiplexing
c. involves the use of a customer premises equipment (CPE)
d. uses a combination of amplitude and phase modulation
e. all of the above
Answer: e, Moderate, p. 101

61. ___________ is one way that data rates over traditional telephone lines can be increased dramatically.
a. SONET
b. T-carrier services
c. CSU/DSU
d. ATM
e. DSL
Answer: e, Moderate, p. 101

Short Answer

1. How does analog data differ from digital data?
Answer: Digital numbers can only have discrete values: 0 or 1. In contrast, telephones produce analog data whose electrical signals are shaped like the sound waves they transfer; they can take on any value in a wide range of possibilities.
2. What is coding?
Answer: A character is a symbol that has a common, constant meaning. Characters in data communications, as in computer systems, are represented by groups of bits that are binary zeros and ones. The groups of bits representing the set of characters that are the “alphabet” of any given system are called a coding scheme, or code.
Coding is representation of characters by a group of bits using a coding scheme such as ASCII.
3. What is QAM?
Answer: Quadrature amplitude modulation is a combined modulation technique. Eight different phases and two different amplitudes are used for a total of 16 different values. One symbol in QAM represents four bits.
4. What is the importance of Trellis-coded Modulation?
Answer: Trellis-coded modulation is an enhancement of QAM that combines phase modulation and amplitude modulation. TCM is unique in that it can transmit a different number of bits on each symbol --- up to eight or ten bits per symbol. They are a ‘high speed’ modulation technique. One disadvantage is that TCM is more sensitive to imperfections in the communication circuit.
5. What data compression standard uses Lempel-Ziv encoding? How does it work?
Answer: V.44, the ISO standard for data compression, uses Lempel-Ziv encoding. As a message is being transmitted, Lempel-Ziv encoding builds a dictionary of two, three, and four character combinations that occur in the message. Any time the same character pattern reoccurs in the message, the index to the dictionary entry is transmitted rather than sending the actual data. The reduction depends on the data sent, but it usually averages 6:1.
6. Describe two ways in which Statistical Time Division Multiplexing (STDM) differs from Time Division Multiplexing (TDM).
Answer: The key benefit of STDM is that it provides more efficient use of the circuit and saves money. STDM allows more terminals or computers to be connected to a circuit than FDM or TDM. You can buy a lower speed, less expensive circuit than you could using FDM or TDM. Unlike TDM, in the case of STDM all data must be identified by an address that specifies the device to which it belongs.
7. Compare and contrast Frequency Division Multiplexing (FDM) and Wavelength Division Multiplexing (WDM)
Answer: Frequency division multiplexing can be described as dividing the circuit “horizontally” so that many signals can travel a single communication circuit simultaneously. The circuit is divided into a series of separate channels, each transmitting on a different frequency, much like series of different radio or TV stations. All signals exist in the media at the same time, but because they are on different frequencies, they do not interfere with each other.
Wavelength division multiplexing is a version of FDM used in fiber optic cables. WDM works by using lasers to transmit different frequencies of light (i.e., colors) through the same fiber optic cable; each channel is assigned a different frequency so that the light generated by one laser does not interfere with the light produced by another.
8. What is an inverse multiplexer? Why would you put one on a network?
Answer: Inverse multiplexing (IMUX) combines several low speed circuits to make them appear as one high speed circuit to the user. As far as the users are concerned, they have access to one high speed circuit, even through their data actually travels across a set of slower circuits.
9. Under what circumstances would you use a microwave circuit rather than a satellite circuit?
Answer: The choice of radiated media depends more on distance than any other factor; infrared and radio are the cheapest for short distances, microwave for moderate distances, and satellite for long distances.
10. Explain two reasons why the use of twisted pair cable is becoming more common than the use of coax cable?
Answer: Among the guided media, twisted pair wire is generally the cheapest. Coaxial cable is somewhat more expensive. In general, both twisted pair and coaxial cable can provide data rates from 1 to 100 Mbps. With twisted pair costing less and providing similar transmission speeds to coax cable, twisted pair cable is becoming more common than the use of coax cable. Also, there is a lot of existing twisted pair cable in homes and offices that are available for use.
11. Thought question: How would you design a network using simplex circuits? What would the network layout look like?
Answer: One could design a network using simplex circuits by thinking of one way streets (a “ring”) or using multiple lines to provide transmission in both directions.
12. Thought question: How would Statistical Frequency Division Multiplexing work if there were such a technique?
Answer: Statistical Frequency Division Multiplexing would have the same number of channels; though, not all of them active. The size of the channel changes as transmissions ebb and flow.