1. technology and computing
2. hardware
3. computer networking
4. router

SAMPLE TEST from past EXAMS
------------------------------------------------------------------------------------------------------------------(This is only a sample collected from previous exams to use as a guide. This semester the
questions may include fill in the blanks and different nature of questions, but mostly from the
text book.)
------------------------------------------------------------------------------------------------------------------You must show the calculations for the descriptive questions.
Notes: Any script without a name will receive no points.
1. Name the three transmission modes.
Name the five types of topology.
Write five components of a data communication system.
2. Write three criteria necessary for an effective and efficient networking.
Write three fundamental characteristics that determine the effectiveness of a data communication
system?
Name three factors that affect the performance of a network.
3.
Define the type of topology in the following figure.
Draw a hybrid topology with a bus backbone connecting two ring backbones. Each ring backbone
connects three star networks.
4.
Two signals have the same frequencies. However, when the first signal is at its maximum amplitude, the second
signal has amplitude of zero. Draw the two signals. What is the phase shift between the two signals?
What is the bandwidth of a signal that ranges from 40 KHz to 4 MHz?
What is the bit rate for a signal in which 10 bits last 20 microseconds.?
5. Assuming six devices are arranged in a mesh topology. How many cables are needed?
How many ports are needed for each device?
6. If we want to transmit 1000 ASCII characters (7 bit) asynchrounously. What is the minimum number of
extra bits needed? What is the efficiency in percentage?
7. Write three elements of a protocol?
Define the syntax and semantics in the following sentence: “The dog drove the car safely to the
destination.” Is the syntax correct? Are the semantics right?
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8. a. A constellation diagram consists of sixteen equally spaced points on a circle. If the bit rate is 4800
bps, what is the baud rate?
b. If the baud rate for a QAM signal is 1800 and the bit rate is 9000, how many points are there in the
constellation?
c. Can a constellation have 128 points? Why or Why not?
9. Name each of the layers in OSI model in order of hierarchy starting with the top layer.
10. What is the difference between network layer delivery and transport layer delivery?
11. What is the difference between a de facto standard and a de jure standard?
Name three standard creation committees.
12. Match the following to one of the seven OSI layers. Write the name of the relevant layer.
a. Reliable end-to-end data transmission.
b. User services such as e-mail and file transfer provided.
c. Transmission of bit stream across physical medium.
d. Establishes, manages, and terminates session.
e. Provides independence from differences in data representation.
f. Synchronizes users.
g. Route determination.
h. Mechanical, electrical, and functional interface.
i. Reassembly of data packets.
j. Responsibility for information between two adjacent nodes.
j. Interface to outside world.
k. ASCII changed to EBCDIC.
l. Packet switching.
m. Network selection.
n. User services such as e-mail and file transfer provided.
o. Error correction and retransmission.
p. Provide format and code conversion services.
q. Ensures reliable transmission of data.
13. Which conversion type involves modulation of a signal?
Calculate the baud rate for 6000 bps signal with 16-QAM.
Calculate the baud rate for 6000bps, tribit combination.
Calculate the bit rate for 1000 baud, 8-PSK.
Draw the constellation diagram for a 2-PSK, amplitude of 1 at 0 and 180 degrees.
14. Data from a source ranges in value between -1.0 and 1.0. To what do the data points 0.91, -0.25, 0.56,
and 0.71 transform if eight bit quantization is used?
Using the Nyquest theorem, calculate the sampling rate for the analogue signal with frequencies from
2000 to 4000 Hz.
If the baud rate for a QAM signal is 1800 and the bit rate is 9000, how many bits are there per signal
element?
15. Compare the two methods of serial transmission. Discuss the advantages and disadvantages of each.
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16. Assume a data stream is made of three zeros followed by two 1s followed by two 0s, and another three
Encode the stream using the following encoding scheme.
a. polar NRZ-L.
b. Manchester coding.
c. Differential Manchester.
Following figure is the Manchester encoding of a data stream. What is the data stream?
What would be the data stream if the above figure is an output of differential Manchester coding?
17. Suppose you add two new devices to an existing five-device network. If you have a fully connected mesh
topology, how many new cable lines are needed?
If, however, the devices are arranged in a ring, how many new cables are needed?
18. What are the responsibilities of data link layer?
19. What is the relationship between period and frequency?
What are units of period and frequency?
What is a bit rate and what is its counterpart in analog signal?
What is a bit interval and what is its counterpart in an analog signal?
20. A receiver received the following 11 bits coded with hamming encoding (bits 1, 2, 4, and 8 as even
parity bits).
11
1
10
1
9
0
8
0
7
1
6
0
5
1
4
0
3
0
2
1
1
1
Find out the 7 data bit sent by the sender (correct if you detect that there was any error during transmission)
21. A receiver received the following 11 bits coded with hamming encoding (bits 1, 2, 4, and 8 as even
parity bits).
11
0
10
1
9
1
8
0
7
0
6
1
5
1
4
1
3
0
2
1
1
0
Find out the 7 data bit sent by the sender (correct if you detect that there was any error during transmission)
22. Construct the Hamming code for the data 1011001. Use odd parity. Show the steps. (use the other side
of the page)
Find the CRC for the data 100101. The divisor is 1101. Show the steps.
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Use Scantron to answer
Notes: Any script without a name will receive no points. It is necessary that you mark the correct answer on
scantron page and also on this paper.
Multiple Choices
1. The network layer lies between the transport layer and the _______ layer.
a. data
b. physical
c. session
d. data link
2. _______ addresses on headers change as a packet moves from network to network but the _______ do not.
a. Logical; port
b. Logical; network
c. Logical; physical
d. Physical; logical
3. In a __________ connection, more than two devices can share a single link.
a. point-to-point
b. multipoint
c. primary
d. secondary
4. XYZ publishing, with headquarters in London and branch offices through-out Asia, Europe, and South America, is
probably connected by a ___________.
a. LAN
b. MAN
c. WAN
d. none of the above
5. The maximum data rate of a half duplex 8-PSK modem using a two-wire regular telephone line is _____ bps.
a. 1200
b. 2400
c. 7200
d. none of the above
6. What is the main function of the transport layer?
a. node-to-node delivery
b. end-to-end message delivery
c. synchronization
d. updating and maintenance of routing table.
7. If the sending system uses ASCII encoding and the receiving station uses EBCDIC encoding, the _______ layer is
responsible for translation.
a. network
b. presentation
c. transport
d. physical
8. Session layer checkpoints _____________
a. allow just a portion of a file to be resent
c. control the addition of headers
b. detect and recover errors
d. are involved in dialog controls.
9. If the baud rate is 1200 and there are 4 bits for each signal element, then the bit rate is _______.
a. 4800 b. 1200 c. 400 d. 300
10. An 8-QAM modulated signal has a baud rate of 2000; the bit rate is _______ bps.
a. 8000 b. 6000 c. 2000 d. 1000
11. A 128-QAM modulated signal has a baud rate of 2000; there are _______ bits per baud.
a. 2000 b. 1000 c. 7 d. 6
12. The modulation technique most affected by noise is _______.
a. ASK b. PSK c. FSK d. QAM
13. Twisted-pair wire, coaxial cable, and fiber-optic cable are all types of _______.
a. protocols b. messages c. media d. data
14. The key element of a protocol is _______.
a. syntax b. semantics c. timing d. all of the above
15. A _______ is a physical communication pathway that transfers data from one device to another.
a. node b. message c. link d. receiver
16. In a multipoint line configuration, _______ devices share a single link.
a. exactly two b. exactly three c. exactly four d. three or more
17. A signal has a constant value of 10 volts. Its frequency is _______ Hz.
a. zero b. one c. ten d. five
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18. _______ refers to the structure or format of the data, the order in which they are presented.
a. Syntax b. Semantics c. Timing d. none of the above
19. _______ refers to the meaning of each section of bits.
a. Syntax b. Semantics c. Timing d. none of the above
20. When a protocol specifies that the address of the sender must occupy the first four bytes of a message, this is a
_______ issue.
a. Syntax b. Semantics c. Timing d. none of the above
21. If the maximum value of a simple sine wave is 10 volts, the voltage values _______.
a. range from 0 to 10, inclusive b. are either 10 or -10 c. range from -10 to 10, inclusive d. are integer values from
-10 to 10
22. The _______ of a signal is its number of cycles per second.
a. amplitude b. frequency c. phase d. any of the above
23. The value of a simple sine wave at time zero is its maximum positive value. The phase shift is therefore _______
degrees.
a. 0 b. 90 c. 180 d. 270
24. A signal with a frequency of 10 MHz has more cycles per second than a signal with a frequency of _______.
a. 10 KHz b. 10 GHz c. 10 THz d. 1 THz
25. A sine wave has a frequency of 10 Hz. Its period is _______.
a. 10 seconds b. 1 second c. 0.1 second d. 0.01 second
26. A digital signal has its 0 bits represented by 0 volts and its 1 bit represented by -5 volts or 5 volts. This is _______
encoding.
a. unipolar b. polar c. bipolar d. b and c
27. The DC component is a serious problem for _______ encoding.
a. unipolar b. polar c. bipolar d. b and c
28. _______ encoding is superior to _______ encoding because the problem of the DC component is alleviated.
a. Unipolar; polar b. Polar; bipolar c. Polar; unipolar d. Unipolar; bipolar
29. Ethernet LANs use _______ encoding.
a. RZ b. Manchester c. differential Manchester d. NRZ-I
30. A simple sine wave completes one cycle in _______ degrees.
a. 45 b. 90 c. 180 d. 360
31. Which of the following is a basic network topology?
a. half-duplex b. multipoint c. ring d. all of the above
32. Seven devices are arranged in a mesh topology. _______ physical channels link these devices.
a. Seven b. Six c. Twenty d. Twenty-one
33. In a _______ topology, a dedicated link connects a device to a central controller.
a. ring b. bus c. mesh d. star
34. A _______ topology is a variation of a star topology.
a. ring b. bus c. mesh d. tree
35. The number of pins, the cable length, and the pin configuration are _______ specifications of the EIA-232 interface
standard.
a. mechanical
b. electrical
c. functional
d. any of the above
36. The data link layer lies between the _______ layer and the network layer.
a. transport
b. session
c. physical
d. application
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37. The header added by the transport layer to the packet coming from the upper layer includes the _______ address.
a. logical
b. service-point
c. physical
d. network
38. The performance of data communication network depends on __________________.
a. the number of users b. the transmission media c. the hardware and software d. all of the above
39. Protection of data from a natural disaster such as a tornado is a network _____________ issue.
a. performance
b. reliability
c. security
d. management
40. There are n devices arranged in a ring topology. A device is deleted. There are now _______ links of cable.
a. n - 1 b. n - 2 c. n d. n + 1
41. The _______ is an example of a simplex device.
a. repeater b. tap c. walkie-talkie d. keyboard
42. E-mail is a service handled by the _______ layer.
a. session
b. presentation
c. application
d. data link
43. In the _______ transmission mode, both stations can transmit and receive at the same time.
a. simplex b. half-duplex c. full-duplex d. b and c
44. A _______ is usually privately owned and links the devices in a single office, building, or campus.
a. LAN b. MAN c. WAN d. all of the above
45. A sampling rate of _______ million samples per second is needed for a signal with components ranging from 10MHz
to 100 MHz.
a. 10
b. 90
c. 100
d. 200
46. In _______ the phase and amplitude of the carrier signal is varied based on the information in a digital signal.
a. ASK
b. PSK
c. FSK
d. QAM
47. For _______, the minimum bandwidth required for transmission is equal to the baud rate.
a. ASK
b. PSK
c. FSK
d. a and b
48. In FM the _______ of the information signal modulates the frequency of the carrier signal.
a. amplitude
b. frequency
c. phase
d. any of the above
49. In which type of modulation can the bit rate be four times the baud rate?
a. ASK
b. FSK
c. PSK
d. None of the above
50. In a dibit modulation, the number of points in the constellation is _______.
a. 2 b. 4 c. 8 d. None of the above
51. An 8-QAM constellation is a _________ modulation.
a. dibit b. tribit c. quadbit d. None of the above
52. Token Ring LANs use _______ encoding.
a. RZ b. Manchester c. differential Manchester d. NRZ-I
53. The frequency of a signal is inversely related to its _______.
a. amplitude b. period c. phase d. any of the above
54. Forty-five physical channels link _______ devices arranged in a mesh topology.
a. nine b. ten c. forty d. forty-five
55. In _______ the phase and amplitude of the carrier signal is varied based on the information in a digital signal.
a. ASK b. PSK c. FSK d. QAM
56. _______ rate is always less than or equal to _______ rate.
a. Baud; bit b. Bit; baud c. Baud; base d. Base; baud
57. [1 point] In _______ transmission, if n bits are being sent simultaneously, n communication channels are needed.
a. parallel
b. synchronous
c. asynchronous
d. serial
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58. _______ transmission features start bits, stop bits, and gaps between data units.
a. Parallel
b. Synchronous
c. Asynchronous
d. Virtual
59. The voltage level and the signal type are _______ specifications of the EIA-232 interface standard.
a. mechanical
b. electrical
c. functional
d. any of the above
60. Error detection is usually done in the _______ layer of the OSI model.
a. physical
b. data link
c. network
d.any of the above
61. The maximum data rate of a full duplex 8-PSK modem using a two-wire regular telephone line is ___________ bps.
a. 1200
b. 3600
c. 7200
d. none of above
62. Radio communication ranges from a frequency of _______ to a frequency of _______.
a. 3 KHz; 300 MHz b. 3 KHz; 300 GHz
c. 3 MHz; 300 GHz
d. 3 GHz; 300 THz
63. The _______ of a signal is the collection of all its component frequencies.
a. amplitude b. frequency spectrum c. phase d. bandwidth
64. The _______ of a signal is the width of its frequency spectrum.
a. bandwidth b. amplitude c. phase d. frequency
65. A signal is decomposed into three sine waves with frequencies of 10, 20, and 30 Hz. The bandwidth of the signal is
_______ Hz.
a. 10 b. 20 c. 30 d. 60
66. The _______ is the number of bits sent in one second.
a. bit interval b. bit rate c. baud d. frequency
67. A bit interval of 10 milliseconds means a bit rate of _______bps.
a. 0.1 b. 1 c. 10 d. 100
68. _______ rate is the number of bits per second; _______ rate is the number of signal units per second.
a. Baud; bit b. Bit; baud c. Baud; base d. Base; baud
69. Which error detection method uses one’s complement arithmetic?
a. VRC
b. LRC
c. CRC
d. checksum
70. Which error detection method involves polynomials?
a. VRC
b. LRC
c. CRC
d. checksum
71. In cyclic redundancy checking, what is the CRC?
a. the divisor
b. the quotient
c. the dividend
d. the remainder
72. In cyclic redundancy checking, the divisor is _______ the CRC.
a. the same size as
b. one bit less than
c. one bit more than
d. two bits more than
73. If the data unit is 111111, the divisor 1010, and the remainder 110, what is the dividend at the receiver?
a. 111111011
b. 111111110
C. 1010110
d. 110111111
74. If the data unit is 111111 and the divisor 1010, what is the dividend at the transmitter
a. 111111000
b. 1111110000
c. 111111
d. 1111111010
75. If odd parity is used for ASCII error detection, the number of Os per eight-bit symbol is
a. even
b. odd
c. indeterminate
d. 42
76. The Hamming code is a method of_______
a. error detection
b. error correction
c. error encapsulation
d. a and b
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77. In CRC there is no error if the remainder at the receiver is ________
a. equal to the remainder at the sender b. zero
c. nonzero
78. In CRC the quotient at the sender _______
a. becomes the dividend at the receiver
c. is discarded
d. the quotient at the sender
b. becomes the divisor at the receiver
d. is the remainder
79. Which error detection method involves the use of parity bits?
a. VRC
b. LRC
c. CRC
d. a and b
80. Which error detection method can detect a single-bit error?
a. VRC
b. LRC
c. CRC
d.
all of the above
81. For 10 groups, each of 8 bits, we calculate the LRC. How many bits make up the LRC?
a. 10
b. 8
c. 18
d. 80
82. At the CRC generator, _______ added to the data unit before the division process.
a. Os are
b. ls are
c. a polynomial is d. a CRC remainder is
83. At the CRC generator, _______ added to the data unit after the division process.
a. Os are
b. 1s are
c. the polynomial is
d. the CRC remainder is
84. At the CRC checker, _______ means that the data unit is damaged.
a. a string of Os
b. a string of 1s
c.a string of alternating is and Os
85. Encryption and decryption are functions of the ______________ layer.
a. transport
b. session
c. presentation
d. a nonzero remainder
d. application
86. The _______ layer is responsible for dialog establishment, maintenance, synchronization, and termination.
a. transport b. session
c. presentation
d. application
87. The ________ layer can disconnect a session abruptly, while the ________ layer provides for graceful closure.
a. session; presentation
b. session; application
c. session: transport
d. transport; session
88. _______ points provide a method to recover data that have been delivered but not yet used.
a. Segmentation
b. Concatenation
c. Translation
d. Synchronization
89. Which of the following is/are presentation layer functions?
a. encryption of data
b. compression of data
c. translation of data
d. all of the above
90. In the conventional method of encryption and decryption, which key is publicly known?
a. Ke only
b. Kd only
c. Ke and Kd
d. none
91. In the public key method of encryption and decryption, which key is publicly known?
a. Ke only
b. Kd only
c. Ke and Kd
d. none
92. In the public key method of encryption and decryption, only the receiver has possession of the ________
a.Ke
b.Kd
c. Ke and Kd
d. none of the above
93. We use an encryption method in which both plaintext and ciphertext have the same number of As, Bs, Cs, and so on.
This is probably _______ substitution.
a. monoalphabetic
b. polyalphabetic
C. transpositional d. rotational
94. We use an encryption method in which the character Z always substitutes for the character G. This is probably
_______ substitution.
a. monoalphabetic
b. polyalphabetic c. transpositional
d. rotational
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95. We use an encryption method in which the plaintext AAAAAA becomes the ciphertext BCDEFG. This is probably
_______ substitution.
a. monoalphabetic
b. polyalphabetic
c. transpositional
d. DES
96. An encryption method used by the U.S. government for nonmilitary and nonclassifled use is ________
a. monoalphabetic substitution
b. polyalphabetic substitution
c. transpositional substitution
d. the data encryption standard
97. In _______ permutation, the number of outputs is greater than the number of inputs.
a. a straight
b. a compressed
c. an expanded
d. a rotational
98. The RSA algorithm is the basis of a _______ encryption method.
a. public key
b. private key
c. conventional
d. denominational
99. The success of the RSA encryption method lies in the difficulty of _______
a. finding Kp
b. finding the prime factors of Kp
c. finding N
d. finding the prime factors of N
100. A string of 100 Os is replaced by a marker, a 0, and the number 100. This is
a. run-length encoding
b. Morse code
c. differential encoding
d. Lempel-Ziv-Welch encoding
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