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.

61. In the TCP/IP protocol suite, which one of the following is NOT part of the IP header?
a. Fragment Offset
b. Source IP address
c. Destination IP address
d. Destination port number
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Answer: (d).Destination port number

62. Suppose that the maximum transmit window size for a TCP connection is 12000 bytes. Each packet consists of 2000 bytes. At some point of time, the connection is in slow-start phase with a current transmit window of 4000 bytes. Subsequently, the transmitter receives two acknowledgements. Assume that no packets are lost and there are no time-outs. What is the maximum possible value of the current transmit window?
a. 4000 bytes
b. 8000 bytes
c. 10000 bytes
d. 12000 bytes
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Answer: (b).8000 bytes

63. Traceroute reports a possible route that is taken by packets moving from some host A to some other host B. Which of the following options represents the technique used by traceroute to identify these hosts
a. By progressively querying routers about the next router on the path to B using ICMP packets, starting with the first router
b. By requiring each router to append the address to the ICMP packet as it is forwarded to B. The list of all routers en-route to B is returned by B in an ICMP reply packet
c. By ensuring that an ICMP reply packet is returned to A by each router en-route to B, in the ascending order of their hop distance from A
d. By locally computing the shortest path from A to B
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Answer: (a).By progressively querying routers about the next router on the path to B using ICMP packets, starting with the first router

64. Count to infinity is a problem associated with
a. link state routing protocol
b. distance vector routing protocol
c. DNS while resolving host name
d. TCP for congestion control
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Answer: (b).distance vector routing protocol

65. In a communication network, a packet of length L bits takes link L1 with a probability of p1or link L2 with a probability of p2. Link L1 and L2 have bit error probability of b1 and b2 respectively. The probability that the packet will be received without error via either L1 or L2 is
a. (1 - b1)Lp1 + (1 - b2)Lp2
b. [1 - (b1 + b2)L]p1p2
c. (1 - b1)L (1 - b2)Lp1p2
d. 1 - (b1Lp1 + b2Lp2)
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Answer: (a).(1 - b1)Lp1 + (1 - b2)Lp2

66. A company has a class C network address of 204.204.204.0. It wishes to have three subnets, one with 100 hosts and two with 50 hosts each. Which one of the following options represents a feasible set of subnet address/subnet mask pairs?
a. 204.204.204.128/255.255.255.192 204.204.204.0/255.255.255.128 204.204.204.64/255.255.255.128
b. 204.204.204.0/255.255.255.192 204.204.204.192/255.255.255.128 204.204.204.64/255.255.255.128
c. 204.204.204.128/255.255.255.128 204.204.204.192/255.255.255.192 204.204.204.224/255.255.255.192
d. 204.204.204.128/255.255.255.128 204.204.204.64/255.255.255.192 204.204.204.0/255.255.255.192
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Answer: (d).204.204.204.128/255.255.255.128 204.204.204.64/255.255.255.192 204.204.204.0/255.255.255.192

67. Assume that "host1.mydomain.dom" has an IP address of 145.128.16.8. Which of the following options would be most appropriate as a subsequence of steps in performing the reverse lookup of 145.128.16.8? In the following options "NS" is an abbreviation of "nameserver".
a. Query a NS for the root domain and then NS for the "dom" domains
b. Directly query a NS for "dom" and then a NS for "mydomain.dom" domains
c. Query a NS for in-addr.arpa and then a NS for 128.145.in-addr.arpa domains
d. Directly query a NS for 145.in-addr.arpa and then a NS for 128.145.in-addr.arpa domains
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Answer: (c).Query a NS for in-addr.arpa and then a NS for 128.145.in-addr.arpa domains

68. An IP datagram of size 1000 bytes arrives at a router. The router has to forward this packet on a link whose MTU (maximum transmission unit) is 100 bytes. Assume that the size of the IP header is 20 bytes. The number of fragments that the IP datagram will be divided into for transmission is :
a. 10
b. 50
c. 12
d. 13
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Answer: (d).13

69. Which of the following statements is TRUE ?
a. Both Ethernet frame and IP packet include checksum fields
b. Ethernet frame includes a checksum field and IP packet includes a CRC field
c. Ethernet frame includes a CRC field and IP packet includes a checksum field
d. Both Ethernet frame and IP packet include CRC fields
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Answer: (c).Ethernet frame includes a CRC field and IP packet includes a checksum field

70. Two popular routing algorithms are Distance Vector(DV) and Link State (LS) routing. Which of the following are true?
(S1) Count to infinity is a problem only with DV and not LS routing
(S2) In LS, the shortest path algorithm is run only at one node
(S3) In DV, the shortest path algorithm is run only at one node
(S4) DV requires lesser number of network messages than LS
a. S1, S2 and S4 only
b. S1, S3 and S4 only
c. S2 and S3 only
d. S1 and S4 only
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Answer: (d).S1 and S4 only

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