# Data Communication and Computer Networks Set 1

## Questions and Answers 1 to 10

 1 Which error detection method consists of a parity bit for each data unit as well as an entire data unit of parity bits? (a)  VRC                                                (b)  LRC                                                (c)  CRC                  (d)  Checksum                                       (e)  None of the above. 2 Which of the following encoding method does not provide for synchronization? (a)  NRZ-L               (b)  RZ                    (c)  B8ZS                (d)  HDB3                (e)  Manchester. 3 Consider the following Fig 1 which consists of five different network topologies In the above figure, which of the following correctly identifies the respective topologies? (a)   Graph, ring, star, unconnected, fully connected (b)   Star, ring , tree, uncompleted, fully connected (c)   Star, rounded, graph, irregular, fully connected (d)   Ring, tree, star,  regular, fully connected (e)   Star, ring, tree, irregular, fully connected. 4 Shannon’s noisy channel capacity theorem states that C = H Log2( 1 + S/N)  bits per second. In this equation H stands for (a)   C is the bandwidth of the signal (b)   H is the bandwidth of the Channel (c)   C is the bandwidth of the Channel (d)   H is the bandwidth of the signal (e)   S/N is in decibels. 5 When signals are used to transmit digital data (a)   Channel of infinite bandwidth must be used for 100% accurate reception of data (b)   A modulation technique must always be used (c)   The data rate is only limited by the bandwidth of the channel used (d)   Data must be decoded on to the signal at the transmitter (e)   The Noise level of the channel can increase the bandwidth. 6 In go-back-n ARQ, if frames 4, 5, 6 are received successfully, What is the ACK number receiver may send to the sender? (a)  5                       (b)  6                       (c)  7                       (d)  8                              (e)  9. 7 Transmitted signals across band limited channels are distorted due to (a)   External interferences. (b)   Attenuation of some of the frequency components (c)   Delays in some frequency components (d)   Reductions in the amplitudes of the transmitted frequency components (e)   Amplification of the unwanted frequency components. 8 The following statements can be made in general on data communication links. I.     Digital data cannot be transmitted along analog transmission links. II.     A modem is an essential component of a serial data link. III.    Full duplex communication is not done on serial transmission. IV.   Parallel links are used in interconnecting subsystems of a computer system. Which of the following statements are correct? (a)   (I) and (IV) are correct, (II) and (III) are incorrect (b)   (I) and (II) are correct, (III) and (IV) are incorrect (c)   (II) and (iv) are correct, (I) and (III) are incorrect (d)   (II) and (III) and (IV) are correct, (I) is incorrect. (e)   (I), (II) and (III) are incorrect, (iv) is correct. 9 In a Bit Oriented Synchronous Transmission Scheme, the bit pattern 1010111111111111110001100000001010111110 has to be transmitted as the frame content. If the opening and the closing flags have the form 01111110, which of the following pattern(s) enable(s) data transparency? (a)   01111110101011111111111111000110000000101011111001111110 (b)   01111110101011111011111011110001100000001010111110001111110 (c)   011111010101011111011111011110001100000001010111110011111010 (d)   0111111010101111110111111011000110000000101011111001111110 (e)   0111111010101111111111111110001100000100101011111001111110. 10 How many bits are allocated for the host part in a class A type of an IP address? (a)  8                       (b)  16                     (c)  24                     (d)  32                               (e)  48.