CH 4&5 T_F Key

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California State University, Fullerton *

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409

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Electrical Engineering

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Jun 21, 2024

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docx

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1. Media access controls refer to the need to control when computers transmit. a. True b. False 2. The data link layer accepts messages from the network layer and controls the hardware that transmits them. a. True b. False 3. 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. True b. False 4. Most computer networks managed by a host mainframe computer tend to use a form of media access control called contention. a. True b. False 5. Polling is the process of permitting all clients to transmit or receive at any time. a. True b. False 6. With roll-call polling, a server polls clients in a consecutive, pre-arranged priority list. a. True b. False 7. 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. a. True b. False 8. With contention, a computer does not have to wait before it can transmit. A computer can transmit at any time. a. True b. False 9. Contention is widely used with Ethernet local area networks. a. True b. False 10. Controlled access MAC approaches work well in a large network with high usage. a. True b. False 11. There are three commonly used controlled access techniques: access requests, access demands, and polling. a. True b. False 12. The two categories of network errors are lost data and delimited data. a. True b. False 13. If a computer transmits a message containing “ABC” and the destination computer receives “abc” as the message, the message is corrupted. a. True b. False 14. Data transmission errors typically are distributed uniformly in time. a. True b. False 15. Undesirable stray electrical voltage can cause data communication errors. a. True b. False

16. Gaussian noise is a special type of attenuation. a. True b. False 17. The thermal agitation of electrons causes impulse noise. a. True b. False 18. Crosstalk occurs when the signal transmitted on one circuit or channel of a transmission system creates an undesired effect in another circuit or channel. a. True b. False 19. Attenuation refers to the loss of signal strength. a. True b. False 20. 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. a. True b. False 21. The physical and data link layers of wired Ethernet have been refined over the years as a collection of standards under the IEEE 802.3 workgroup. a. True b. False 22. The distance between repeaters or amplifiers on a telephone circuit is determined by the amount of power gained per unit length of the transmission. a. True b. False 23. When we amplify the signal on an analog circuit, we also amplify any noise that is present on the circuit. a. True b. False 24. For effective error detection and correction, extra error detection “data” must be included with each message a. True b. False 25. 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. a. True b. False 26. Parity checking can only detect an error when an even number of bits are switched. a. True b. False 27. Cyclical redundancy check is one of the most popular polynomial error-checking schemes. a. True b. False 28. The simplest method for error correction is retransmission. a. True b. False 29. Another term for continuous ARQ is sliding window. a. True b. False 30. One type of forward error correction is the Hamming code. a. True b. False

31. Forward error correction is commonly used in satellite transmission. a. True b. False 32. HDLC is very similar to the SDLC synchronous data link protocol. a. True b. False 33. Overhead bits are used for error checking and marking the start and end of characters and packets. a. True b. False 34. Transmission efficiency refers to the percentage of bits transmitted without errors. a. True b. False 35. The data link layer accepts streams of bits from the application layer. a. True b. False 36. The data link layer is responsible for encoding the bit-stream as a series of electronic voltages. a. True b. False 37. The data link layer performs error detection. a. True b. False 38. The data link layer performs routing functions. a. True b. False 39. The data link layer organizes data from the physical layer and passes these coherent messages directly to the application layer. a. True b. False 40. Media access control is not very important in point-to-point with full duplex configuration. a. True b. False 41. Media access control is not very important in local area networks. a. True b. False 42. Media access control is not very important in a point-to-point with a half-duplex configuration. a. True b. False 43. Media access control is not very important in a multipoint configuration. a. True b. False 44. Media access control does not control when computers transmit. a. True b. False 45. Roll call polling cannot be modified to increase priority of clients or terminals. a. True b. False 46. Roll call polling does not require a server, host, or special device that performs the polling. a. True b. False 47. Roll call polling is also called token passing. a. True b. False

48. Roll call polling is a type of contention approach to media access control. a. True b. False 49. Roll call polling typically involves some waiting because the server has to wait for a response from the polled client or terminal. a. True b. False 50. In general, controlled approaches work better than contention approaches for small networks that have low usage. a. True b. False 51. In general, controlled approaches work better than contention approaches for large networks that have high usage. a. True b. False 52. In general, controlled approaches work better than contention approaches for all sizes of networks. a. True b. False 53. In general, controlled approaches do not require a host, server, or active monitor to assign media access control. a. True b. False 54. In general, controlled approaches have many collisions. a. True b. False 55. Using parity, the probability for detecting an error, given that one has occurred, is about 50% for either even or odd parity. a. True b. False 56. Using parity, the probability for detecting an error, given that one has occurred, is about 25% for either even or odd parity. a. True b. False 57. Using parity, the probability for detecting an error, given that one has occurred, is about 70% for even parity and 30% for odd parity. a. True b. False 58. Using parity, the probability for detecting an error, given that one has occurred, is about 30% for even parity and 70% for odd parity. a. True b. False 59. Using parity, the probability for detecting an error, given that one has occurred, is about 20% for either even or odd parity. a. True b. False 60. Using parity, the probability for detecting an error, given that one has occurred, is about 100% for either even or odd parity. a. True b. False 61. Synchronous transmission cannot be used on multipoint circuits. a. True b. False

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