Computer Network Multiple Choice Questions with Answers Set-8

This post contains a computer network related to 20 multiple-choice questions (CN SET-8) that help you to go through the subject and prepare you for Computer network related questions in competitive exams.

Computer Network MCQ Test Series Set-8

Total Number of Questions: 20
Each question carries equal marks i.e 1
No Negative Marking

Page 1 of 2

Consider the three-way handshake mechanism followed during TCP connection establishment between hosts P and Q, Let X and Y be two random 32-bit starting sequence numbers chosen by P and Q respectively. Suppose P sends a TCP connection request message to Q with a TCP segment having SYN bit=1, SEQ number=X and ACK bit=0. Suppose Q accepts the connection request. Which one of the following choices represents the information present in the TCP segment header that is sent by Q to P?

A.SYN bit=1, SEQ number=X+1, ACK bit=0, ACK number=Y, FIN bit=0

B.SYN bit=0, SEQ number=X+1, ACK bit=0, ACK number=Y, FIN bit=1

C.SYN bit=1, SEQ number=Y, ACK bit=1, ACK number=X+1, FIN bit=0

D.SYN bit=1, SEQ number=Y, ACK bit=1, ACK number=X, FIN bit=0

2. Match the following:

Field	Length in bits
P. UDP Header’s Port Number	I. 48
Q. Ethernet MAC Address	II. 8
R. IPv6 Next Header	III. 32
S. TCP Header’s Sequence Number	IV. 16

A.P-III, Q-IV, R-II, S-I

B.P-II, Q-I, R-IV, S-III

C.P-IV, Q-I, R-II, S-III

D.P-IV, Q-I, R-III, S-II

Assume that a 12-bit Hamming codeword consisting of 8-bit data and 4 check bits is $d_8d_7d_6d_5d_4d_3d_2c_4d_1c_2c_1$, where the data bits and the check bits are given in the following tables:

Data Bits
$d_{8}$	$d_{7}$	$d_{6}$	$d_{5}$	$d_{4}$	$d_{3}$	$d_{2}$	$d_{1}$
1	1	0	X	0	1	0	1

Check Bits
$c_{8}$	$c_{4}$	$c_{2}$	$c_{1}$
y	0	1	0

Which one of the following choices gives the correct values of x and y?

A.x is 0 and y is 0.

B.x is 0 and y is 1.

C.x is 1 and y is 0.

D.x is 1 and y is 1.

Consider the following statements regarding the slow start phase of the TCP congestion control algorithm. Note that cwnd stands for the TCP congestion window and MSS denotes the Maximum Segment Size.

(i) The cwnd increases by 2 MSS on every successful acknowledgment.

(ii) The cwnd approximately doubles on every successful acknowledgement.

(iii) The cwnd increases by 1 MSS every round trip time.

(iv) The cwnd approximately doubles every round trip time.

Which one of the following is correct?

A.Only (ii) and (iii) are true

B.Only (i) and (iii) are true

C.Only (iv) is true

D.Only (i) and (iv) are true

5. Consider the following statements about the functionality of an IP-based router.

A router does not modify the IP packets during forwarding.
It is not necessary for a router to implement any routing protocol.
A router should reassemble IP fragments if the MTU of the outgoing link is larger than the size of the incoming IP packet.

Which of the above statements is/are TRUE?

A.1 and 2 only

B.1 only

C.2 and 3 only

D.2 only

Which of the following protocol pairs can be used to send and retrieve e-mails (in that order)?

A.IMAP, POP3

B.SMTP, POP3

C.SMTP, MIME

D.MAP, SMTP

Consider the cyclic redundancy check (CRC) based error detecting scheme having the generator polynomial $X^3+X+1$. Suppose the message $m_4 m_3 m_1 m_0 =11000$ is to transmitted. Check bits $c_2 c_1 c_0$ are appended at the end of the message by the transmitter using the above CRC scheme. The transmitted bit string is denoted by $m_4 m_3 m_2 m_1 m_0 C_2 C_1 C_0$ is

A.101

B.110

C.100

D.111

Consider three machines M, N, and P with IP addresses 100.10.5.2, 100.10.5.5, and 100.10.5.6 respectively. The subnet mask is set to 255.255.255.252 for all three machines. Which one of the following is true?

A.M, N, and Pall belong to the same subnet

B.Only M and N belong to the same subnet

C.Only N and P belong to the same subnet

D.M, N, and P belong to three different subnets

Suppose that in an IP-over-Ethernet network, machine X wishes to find the MAC address of another machine Y in its subnet. Which one of the following techniques can be used for this?

A.X sends an ARP request packet to the local gateway's IP address which then finds the MAC address of Y and sends to X

B.X sends an ARP request packet to the local gateway's MAC address which then finds the MAC address of Y and sends to X

C.X sends an ARP request packet with a broadcast MAC address in its local subnet

D.X sends an ARP request packet with a broadcast IP address in its local subnet

10.

A TCP server application is programmed to listen on port number P on host S. A TCP client is connected to the TCP server over the network.

Consider that while the TCP connection was active, the server machine S crashed and rebooted. Assume that the client does not use the TCP keepalive timer.

Which of the following behaviours is/are possible?

A.If the client was waiting to receive a packet, it may wait indefinitely.

B.The TCP server application on S can listen on P after reboot.

C.If the client sends a packet after the server reboot, it will receive an RST segment.

D.If the client sends a packet after the server reboot, it will receive a FIN segment.

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11. An organization required a range of IP addresses to assign one to each of its 1500 computers. The organization has approached an Internet Service Provider (ISP) for this task. The ISP uses CIDR and serves the requests from the available IP address space 202.61.0.0/17. The ISP wants to assign address space to the organization which will minimize the number of routing entries in the ISP’s router using route aggregation. Which of the following address spaces are potential candidates from which the ISP can allot anyone to the organization?

202.61.84.0/21
202.61.104.0/21
202.61.64.0/21
202.61.144.0/21

A.1 and 2 only

B.2 and 3 only

C.3 and 4 only

D.1 and 4 only

12.

Consider two hosts P and Q connected through a router R. The maximum transfer unit (MTU) value of the link between P and R is 1500 bytes, and between R and Q is 820 bytes.

A TCP segment of size 1400 bytes was transferred from P to Q through R, with an IP identification value of 0x1234. Assume that the IP header size is 20 bytes. Further, the packet is allowed to be fragmented, i.e., the Don’t Fragment (DF) flag in the IP header is not set by P.

A.Two fragments are created at R and the IP datagram size carrying the second fragment is 620 bytes.

B.If the second fragment is lost, R will resend the fragment with the IP identification value 0x1234.

C.If the second fragment is lost, P is required to resend the whole TCP segment.

D.TCP destination port can be determined by analyzing only the second fragment.

13.

Consider a computer network using the distance-vector routing algorithm in its network layer. The partial topology of the network is as shown below.

The objective is to find the shortest-cost path from the router R to routers P and Q. Assume that R does not initially know the shortest routes to P and Q. Assume that R has three neighbouring routers denoted as X, Y, and Z. During one iteration, R measures its distance t its neighbours X, Y, and Z as 3, 2, and 5, respectively. Router R gets routing vectors from its neighbours that indicate that the distance t router P from routers X, Y, and X are 7, 6, and 5, respectively. The routing vector also indicates that the distance to router Q from routers X, Y, and Z are 4, 6, and 8, respectively. Which of the following statement(s) is/are correct with respect to the new routing table of R, after updating during this iteration?

A.The distance from R to P will be stored as 10.

B.The distance from R to Q will be stored as 7.

C.The next-hop router for a packet from R to P is Y.

D.The next-hop router for a packet from R to Q is Z

14.

Assume that you have made a request for a web page through your web browser to a web server. Initially, the browser cache is empty. Further, the browser is configured to send HTTP requests in non-persistent mode. The web page contains text and five very small images. The minimum number of TCP connections required to display the web page completely in your browser is

A.6

B.7

C.8

D.9

15.

Consider a long-lived TCP session with an end-to-end bandwidth of 1 Gbps (= 109 bits-per second). The session starts with a sequence number of 1234. The minimum time (in seconds, rounded to the closest integer) before this sequence number can be used again is _____.

A.between 34 to 35

B.between 32 to 33

C.between 27 to 28

D.between 35 to 36

16. Consider the sliding window flow-control protocol operating between a sender and a receiver over a full-duplex error-free link. Assume the following :

The Time taken for processing the data frame by the receiver is negligible.
The Time taken for processing the acknowledgement frame by the sender is negligible.
The sender has infinite number of frames available for transmission.
The size of the data frame is 2,000 bits and the size of the acknowledgement frame is 10 bits.
The link data rate in each direction is 1 Mbp(= bits per second).
One way propagation delay of the link is 100 milliseconds.

The minimum value of the sender’s window size in terms of the number of frames, (rounded to the nearest integer) needed to achieve a link utilization of 50% is

A.Between 54 to 56

B.Between 47 to 49

C.Between 50 to 52

D.Between 45 to 46

17.

Consider that 15 machines need to be connected in a LAN using 8-port Ethernet Switches. Assume that these switches do not have any separate uplink ports. The minimum number of switches needed is

A.1

B.2

C.3

D.4

18. A five-stage pipeline has stage delays of 150, 120, 150, 160 and 140 nanoseconds.

The registers that are used between the pipeline stages have a delay of 5 nanoseconds each.

The total time to execute 100 independent instructions on this pipeline, assuming there are no pipeline stalls, is

____ nanoseconds.

A.17160

B.21160

C.16170

D.15160

19.

Consider a network using the pure ALOHA medium access control protocol, where each frame is of length 1,000 bits. The channel transmission rate is $1 Mbps(=10^6 bit per second)$. The aggregate number of transmissions across all the nodes (including new frame transmissions and retransmitted frames due to collisions) is modelled as a Poisson process with a rate of 1,000 frames per second. Throughput is defined as the average number of frames successfully transmitted per second. The throughput is defined as the average number of frames successfully transmitted per second. The throughput of the network (rounded to the nearest integer) is____________

A.130 to 140

B.140 to 150

C.160 to 170

D.170 to 180

20.

Consider a TCP connection between a client and a server with the following specifications: the round trip time is 6 ms, the size of the receiver advertised window is 50 KB, the slow-start threshold at the client is 32 KB, and the maximum segment size is 2 KB. The connection is established at time t=0. Assume that there are no timeouts and errors during transmission. Then the size of the congestion window (in KB) at time t+60 ms after all acknowledgements are processed is

A.40

B.42

C.43

D.44

Computer Network MCQ Test Series Set-8

Total Number of Questions: 20

Each question carries equal marks i.e 1

No Negative Marking

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