81. A node X on a 10 Mbps network is regulated by a token bucket. The token bucket is filled at a rate of 2 Mbps. Token bucket is initially filled with 16 megabits. The maximum duration taken by X to transmit at full rate of 10 Mbps is ............ secs.
a. 1
b. 2
c. 3
d. 4
Answer: (b).2

82. Which of the following statements is not true with respect to microwaves?
a. Electromagnetic waves with frequencies from 300 GHz to 400 THz.
b. Propagation is line-of-sight.
c. Very high-frequency waves cannot penetrate walls.
d. Use of certain portions of the band requires permission from authorities.
Answer: (a).Electromagnetic waves with frequencies from 300 GHz to 400 THz.

83. In a fast Ethernet cabling, 100 Base-TX uses ........... cable and maximum segment size is ............
a. twisted pair, 100 metres
b. twisted pair, 200 metres
c. fibre optics, 1000 metres
d. fibre optics, 2000 metres
Answer: (a).twisted pair, 100 metres

84. A network with bandwidth of 10 Mbps can pass only an average of 12,000 frames per minute with each frame carrying an average of 10,000 bits. What is the throughput of this network ?
a. 1 Mbps
b. 2 Mbps
c. 10 Mbps
d. 12 Mbps
Answer: (b).2 Mbps

85. Match the following:

List – I                           List – II
a. Session layer           i. Virtual terminal software
b. Application layer     ii. Semantics of the information transmitted
c. Presentation layer   iii. Flow control
d. Transport layer         iv. Manage dialogue control

Codes :
      a   b   c   d
a. iv   i    ii   iii
b. i    iv   ii   iii
c. iv  i    iii   ii
d. iv  ii    i   iii
Answer: (a).iv   i    ii   iii

86. Which of the following protocols is used by email server to maintain a central repository that can be accessed from any machine?
a. POP3
Answer: (b).IMAP

87. An attacker sits between the sender and receiver and captures the information and retransmits to the receiver after some time without altering the information. This attack is called as ..............
a. Denial of service attack
b. Masquarade attack
c. Simple attack
d. Complex attack
Answer: (a).Denial of service attack

88. Suppose transmission rate of a channel is 32 kbps. If there are ‘8’ routes from source to destination and each packet p contains 8000 bits. Total end to end delay in sending packet P is ................
a. 2 sec
b. 3 sec
c. 4 sec
d. 1 sec
Answer: (a).2 sec

89. Consider the following statements :

a. High speed Ethernet works on optic fiber.
b. A point to point protocol over Ethernet is a network protocol for encapsulating PPP frames inside Ethernet frames.
c. High speed Ethernet does not work on optic fiber.
d. A point to point protocol over Ethernet is a network protocol for encapsulating Ethernet frames inside PPP frames.

Which of the following is correct ?
a. a and b are true; c and d are false
b. a and b are false; c and d are true
c. a, b, c and d are true
d. a, b, c and d are false
Answer: (a).a and b are true; c and d are false

90. In CRC checksum method, assume that given frame for transmission is 1101011011 and the generator polynomial is G(x) = x^4 + x + 1.

After implementing CRC encoder, the encoded word sent from sender side is .............
a. 11010110111110
b. 11101101011011
c. 110101111100111
d. 110101111001111
Answer: (a).11010110111110