A directory of Objective Type Questions covering all the Computer Science subjects. Here you can access and discuss Multiple choice questions and answers for various compitative exams and interviews.

21. 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
View Answer Report Discuss Too Difficult! Search Google
Answer: (b).Packet switching results in less variation in delay than circuit switching

22. 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
View Answer Report Discuss Too Difficult! Search Google
Answer: (c).CSMA/CD is not suitable for a high propagation delay network like satellite network

23. 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
View Answer Report Discuss Too Difficult! Search Google
Answer: (d).Bridge reduces broadcast domain

24. A network with CSMA/CD protocol in the MAC layer is running at 1 Gbps over a 1 km cable with no repeaters. The signal speed in the cable is 2 x 108 m/sec. The minimum frame size for this network should be
a. 10000 bits
b. 10000 bytes
c. 5000 bits
d. 5000 bytes
View Answer Report Discuss Too Difficult! Search Google
Answer: (a).10000 bits

25. A channel has a bit rate of 4 kbps and one-way propagation delay of 20 ms. The channel uses stop and wait protocol. The transmission time of the acknowledgement frame is negligible. To get a channel efficiency of at least 50%, the minimum frame size should be
a. 80 bytes
b. 80 bits
c. 160 bytes
d. 160 bits
View Answer Report Discuss Too Difficult! Search Google
Answer: (d).160 bits

26. In a TDM medium access control bus LAN, each station is assigned one time slot per cycle for transmission. Assume that the length of each time slot is the time to transmit 100 bits plus the end-to-end propagation delay. Assume a propagation speed of 2 x 10^8 m/sec. The length of the LAN is 1 km with a bandwidth of 10 Mbps. The maximum number of stations that can be allowed in the LAN so that the throughput of each station can be 2/3 Mbps is
a. 3
b. 5
c. 10
d. 20
View Answer Report Discuss Too Difficult! Search Google
Answer: (c).10

27. Consider the following message M = 1010001101. The cyclic redundancy check (CRC) for this message using the divisor polynomial x^5 + x^4 + x^2 + 1 is :
a. 01110
b. 01011
c. 10101
d. 10110
View Answer Report Discuss Too Difficult! Search Google
Answer: (a).01110

28. A sender uses the Stop-and-Wait ARQ protocol for reliable transmission of frames. Frames are of size 1000 bytes and the transmission rate at the sender is 80 Kbps (1Kbps = 1000 bits/second). Size of an acknowledgement is 100 bytes and the transmission rate at the receiver is 8 Kbps. The one-way propagation delay is 100 milliseconds. Assuming no frame is lost, the sender throughput is __________ bytes/second.
a. 2500
b. 2000
c. 1500
d. 500
View Answer Report Discuss Too Difficult! Search Google
Answer: (a).2500

29. 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
View Answer Report Discuss Too Difficult! Search Google
Answer: (d).The exponential backoff mechanism reduces the probability of collision on retransmissions

30. A network has a data transmission bandwidth of 20 × 10 6 bits per second. It uses CSMA/CD in the MAC layer. The maximum signal propagation time from one node to another node is 40 microseconds. The minimum size of a frame in the network is _________ bytes.
a. 200
b. 250
c. 400
d. 1200
View Answer Report Discuss Too Difficult! Search Google
Answer: (a).200

Page 3 of 13