Most frequently asked questions Series 1

1) In an Ethernet local area network, which one of the following statements is TRUE ?
a. 
A station stops to sense the channel once it starts transmitting a frame
b. 
The purpose of the jamming signal is to pad the frames that are smaller than the minimum frame size
c.
A station continues to transmit the packet even after the collision is detected
d.
The exponential backoff mechanism reduces the probability of collision on retransmissions

2) Which of the following statements is FALSE regarding a bridge?

a. 
Bridge is a layer 2 device
b. 
Bridge reduces collision domain
c.
Bridge is used to connect two or more LAN segments
d.
Bridge reduces broadcast domain

3) Which of the following statements is TRUE about CSMA/CD ?

a. 
IEEE 802.11 wireless LAN runs CSMA/CD protocol
b. 
Ethernet is not based on CSMA/CD protocol
c.
CSMA/CD is not suitable for a high propagation delay network like satellite network
d.
There is no contention in a CSMA/CD network

4) Which one of the following statements is FALSE ?

a. 
Packet switching leads to better utilization of bandwidth resources than circuit switching
b. 
Packet switching results in less variation in delay than circuit switching
c.
Packet switching requires more per packet processing than circuit switching
d.
Packet switching can lead to reordering unlike in circuit switching

5) In serial data transmission, every byte of data is padded with a ‘0’ in the beginning and one or two ‘I’ s at the end of byte because

a. 
Receiver is to be synchronized for byte reception
b. 
Receiver recovers lost ‘0’ and ‘1’s from these padded bits
c.
Padded bits are useful in parity computation
d.
None of these

6) 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. 
(1-p)^(n-1)
b. 
np(1-p)^(n-1)
c.
p(1-p)^(n-1)
d.
1-(1-p)^(n-1)

7) 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

8) 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

Answers

1) d

2) d

3) c

4) b

5) a

6) b

7) b

8) c