1 SAMPLE TEST from past EXAMS ... - Krypton

SAMPLE TEST from past EXAMS-------------------------------------------------------------------------------------------------------------------(This is only a sample collected from previous exams to use as a guide. This semester thequestions may include fill in the blanks and different nature of questions, but mostly from thetext 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 communicationsystem?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 backboneconnects three star networks.4. Two signals have the same frequencies. However, when the first signal is at its maximum amplitude, the secondsignal 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 ofextra 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 thedestination.” Is the syntax correct? Are the semantics right?1

8. a. A constellation diagram consists of sixteen equally spaced points on a circle. If the bit rate is 4800bps, 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 theconstellation?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 from2000 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 signalelement?15. Compare the two methods of serial transmission. Discuss the advantages and disadvantages of each.2

16. Assume a data stream is made of three zeros followed by two 1s followed by two 0s, and another threeEncode 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 meshtopology, 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 evenparity bits).11 10 9 8 7 6 5 4 3 2 11 1 0 0 1 0 1 0 0 1 1Find 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 evenparity bits).11 10 9 8 7 6 5 4 3 2 10 1 1 0 0 1 1 1 0 1 0Find 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 sideof the page)Find the CRC for the data 100101. The divisor is 1101. Show the steps.3

Use Scantron to answerNotes: Any script without a name will receive no points. It is necessary that you mark the correct answer onscantron page and also on this paper.Multiple Choices1. The network layer lies between the transport layer and the _______ layer.a. data b. physical c. session d. data link2. _______ 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; logical3. In a __________ connection, more than two devices can share a single link.a. point-to-point b. multipoint c. primary d. secondary4. XYZ publishing, with headquarters in London and branch offices through-out Asia, Europe, and South America, isprobably connected by a ___________.a. LAN b. MAN c. WAN d. none of the above5. 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 above6. What is the main function of the transport layer?a. node-to-node delivery b. end-to-end message deliveryc. 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 isresponsible for translation.a. network b. presentation c. transport d. physical8. Session layer checkpoints _____________a. allow just a portion of a file to be resent b. detect and recover errorsc. control the addition of headers 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. 30010. An 8-QAM modulated signal has a baud rate of 2000; the bit rate is _______ bps.a. 8000 b. 6000 c. 2000 d. 100011. A 128-QAM modulated signal has a baud rate of 2000; there are _______ bits per baud.a. 2000 b. 1000 c. 7 d. 612. The modulation technique most affected by noise is _______.a. ASK b. PSK c. FSK d. QAM13. Twisted-pair wire, coaxial cable, and fiber-optic cable are all types of _______.a. protocols b. messages c. media d. data14. The key element of a protocol is _______.a. syntax b. semantics c. timing d. all of the above15. A _______ is a physical communication pathway that transfers data from one device to another.a. node b. message c. link d. receiver16. In a multipoint line configuration, _______ devices share a single link.a. exactly two b. exactly three c. exactly four d. three or more17. A signal has a constant value of 10 volts. Its frequency is _______ Hz.a. zero b. one c. ten d. five4

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 above19. _______ refers to the meaning of each section of bits.a. Syntax b. Semantics c. Timing d. none of the above20. 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 above21. 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 1022. The _______ of a signal is its number of cycles per second.a. amplitude b. frequency c. phase d. any of the above23. 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. 27024. 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 THz25. 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 second26. 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 c27. The DC component is a serious problem for _______ encoding.a. unipolar b. polar c. bipolar d. b and c28. _______ 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; bipolar29. Ethernet LANs use _______ encoding.a. RZ b. Manchester c. differential Manchester d. NRZ-I30. A simple sine wave completes one cycle in _______ degrees.a. 45 b. 90 c. 180 d. 36031. Which of the following is a basic network topology?a. half-duplex b. multipoint c. ring d. all of the above32. Seven devices are arranged in a mesh topology. _______ physical channels link these devices.a. Seven b. Six c. Twenty d. Twenty-one33. In a _______ topology, a dedicated link connects a device to a central controller.a. ring b. bus c. mesh d. star34. A _______ topology is a variation of a star topology.a. ring b. bus c. mesh d. tree35. The number of pins, the cable length, and the pin configuration are _______ specifications of the EIA-232 interfacestandard.a. mechanical b. electrical c. functional d. any of the above36. The data link layer lies between the _______ layer and the network layer.a. transport b. session c. physical d. application5

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. network38. 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 above39. Protection of data from a natural disaster such as a tornado is a network _____________ issue.a. performance b. reliability c. security d. management40. 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 + 141. The _______ is an example of a simplex device.a. repeater b. tap c. walkie-talkie d. keyboard42. E-mail is a service handled by the _______ layer.a. session b. presentation c. application d. data link43. 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 c44. 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 above45. A sampling rate of _______ million samples per second is needed for a signal with components ranging from 10MHzto 100 MHz. a. 10 b. 90 c. 100 d. 20046. 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. QAM47. For _______, the minimum bandwidth required for transmission is equal to the baud rate.a. ASK b. PSK c. FSK d. a and b48. In FM the _______ of the information signal modulates the frequency of the carrier signal.a. amplitude b. frequency c. phase d. any of the above49. 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 above50. In a dibit modulation, the number of points in the constellation is _______.a. 2 b. 4 c. 8 d. None of the above51. An 8-QAM constellation is a _________ modulation.a. dibit b. tribit c. quadbit d. None of the above52. Token Ring LANs use _______ encoding.a. RZ b. Manchester c. differential Manchester d. NRZ-I53. The frequency of a signal is inversely related to its _______.a. amplitude b. period c. phase d. any of the above54. Forty-five physical channels link _______ devices arranged in a mesh topology.a. nine b. ten c. forty d. forty-five55. 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. QAM56. _______ rate is always less than or equal to _______ rate.a. Baud; bit b. Bit; baud c. Baud; base d. Base; baud57. [1 point] In _______ transmission, if n bits are being sent simultaneously, n communication channels are needed.a. parallel b. synchronous c. asynchronous d. serial6

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 d. the quotient at the sender78. In CRC the quotient at the sender _______a. becomes the dividend at the receiver b. becomes the divisor at the receiverc. is discarded d. is the remainder79. Which error detection method involves the use of parity bits?a. VRC b. LRC c. CRC d. a and b80. Which error detection method can detect a single-bit error?a. VRC b. LRC c. CRC d. all of the above81. 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. 8082. 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 is83. 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 is84. 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 d. a nonzero remainder85. Encryption and decryption are functions of the ______________ layer.a. transport b. session c. presentation d. application86. The _______ layer is responsible for dialog establishment, maintenance, synchronization, and termination.a. transport b. session c. presentation d. application87. The ________ layer can disconnect a session abruptly, while the ________ layer provides for graceful closure.a. session; presentation b. session; applicationc. session: transport d. transport; session88. _______ points provide a method to recover data that have been delivered but not yet used.a. Segmentation b. Concatenation c. Translation d. Synchronization89. Which of the following is/are presentation layer functions?a. encryption of data b. compression of datac. translation of data d. all of the above90. In the conventional method of encryption and decryption, which key is publicly known?a. Ke only b. Kd only c. Ke and Kd d. none91. 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. none92. 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 above93. 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. rotational94. 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. rotational8

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. DES96. An encryption method used by the U.S. government for nonmilitary and nonclassifled use is ________a. monoalphabetic substitution b. polyalphabetic substitutionc. transpositional substitution d. the data encryption standard97. In _______ permutation, the number of outputs is greater than the number of inputs.a. a straight b. a compressed c. an expanded d. a rotational98. The RSA algorithm is the basis of a _______ encryption method.a. public key b. private key c. conventional d. denominational99. The success of the RSA encryption method lies in the difficulty of _______a. finding Kp b. finding the prime factors of Kpc. finding N d. finding the prime factors of N100. A string of 100 Os is replaced by a marker, a 0, and the number 100. This isa. run-length encoding b. Morse codec. differential encoding d. Lempel-Ziv-Welch encoding9