1.  Determine the maximum length of the cable (in km) for transmitting data at a rate of 500 Mbps in an Ethernet LAN with frames of size 10,000 bits. Assume the signal speed in the cable to be 2,00,000 km/s. 
a.  1 
b.  2 
c.  2.5 
d.  5 
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Answer: (b).2

2.  Let G(x) be the generator polynomial used for CRC checking. What is the condition that should be satisfied by G(x) to detect odd number of bits in error? 
a.  G(x) contains more than two terms 
b.  G(x) does not divide 1+x^k, for any k not exceeding the frame length 
c.  1+x is a factor of G(x) 
d.  G(x) has an odd number of terms 
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Answer: (c).1+x is a factor of G(x)

3.  Frames of 1000 bits are sent over a 10^6 bps duplex link between two hosts. The propagation time is 25ms. Frames are to be transmitted into this link to maximally pack them in transit (within the link). What is the minimum number of bits (i) that will be required to represent the sequence numbers distinctly? Assume that no time gap needs to be given between transmission of two frames. 
a.  i = 2 
b.  i = 3 
c.  i = 4 
d.  i = 5 
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Answer: (d).i = 5

4.  In Ethernet when Manchester encoding is used, the bit rate is: 
a.  Half the baud rate 
b.  Twice the baud rate 
c.  Same as the baud rate 
d.  None of the above 
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Answer: (a).Half the baud rate

5.  There are n stations in a slotted LAN. Each station attempts to transmit with a probability p in each time slot. What is the probability that ONLY one station transmits in a given time slot? 
a.  (1p)^(n1) 
b.  np(1p)^(n1) 
c.  p(1p)^(n1) 
d.  1(1p)^(n1) 
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Answer: (b).np(1p)^(n1)

6.  In a token ring network the transmission speed is 10^7 bps and the propagation speed is 200 metres/micro second. The 1bit delay in this network is equivalent to: 
a.  500 metres of cable 
b.  200 metres of cable 
c.  20 metres of cable 
d.  50 metres of cable 
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Answer: (c).20 metres of cable

7.  The message 11001001 is to be transmitted using the CRC polynomial x^3 + 1 to protect it from errors. The message that should be transmitted is: 
a.  11001001000 
b.  11001001011 
c.  11001010 
d.  110010010011 
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Answer: (b).11001001011

8.  Consider a token ring network with a length of 2 km having 10 stations including a monitoring station. The propagation speed of the signal is 2 × 10^8 m/s and the token transmission time is ignored. If each station is allowed to hold the token for 2 μsec, the minimum time for which the monitoring station should wait (in μsec)before assuming that the token is lost is _______. 
a.  28 to 30 
b.  20 to 22 
c.  0 to 2 
d.  31 to 33 
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Answer: (a).28 to 30

9.  Consider a selective repeat sliding window protocol that uses a frame size of 1 KB to send data on a 1.5 Mbps link with a oneway latency of 50 msec. To achieve a link utilization of 60%, the minimum number of bits required to represent the sequence number field is ________. 
a.  3 
b.  4 
c.  5 
d.  6 
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Answer: (c).5

10.  A bitstuffing based framing protocol uses an 8bit delimiter pattern of 01111110. If the output bitstring after stuffing is 01111100101, then the input bitstring is 
a.  0111110100 
b.  0111110101 
c.  0111111101 
d.  0111111111 
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Answer: (b).0111110101
