MCQOPTIONS
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MCQOPTIONS
This section includes 101 Mcqs, each offering curated multiple-choice questions to sharpen your Computer Networks knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
An organization has a class-B network and wishes to form subnets for 64 departments. The subnet mask would be |
| A. | 255.255.0.0 |
| B. | 255.255.64.0 |
| C. | 255.255.1.28.0 |
| D. | 255.255.252.0 |
| Answer» E. | |
| 52. |
The message 11001001 is to be transmitted using the CRC polynomial x |
| A. | 11001001000 |
| B. | 11001001011 |
| C. | 11001010 |
| D. | 110010010011 |
| Answer» C. 11001010 | |
| 53. |
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 these |
| Answer» B. twice the baud rate | |
| 54. |
For which one of the following reasons does Internet Protocol (IP) use the Time To Live (TTL) field in the IP datagram header? |
| A. | Ensure packets reach destination within that time |
| B. | Discard packets that reach later than that time |
| C. | Prevent packets from looping indefinitely |
| D. | Limit the time for which a packet gets queued in intermediate routers |
| Answer» D. Limit the time for which a packet gets queued in intermediate routers | |
| 55. |
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 |
| A. | 28 to 30 sec. |
| B. | 21 to 30 sec. |
| C. | 20 to 24 sec. |
| D. | 38 to 40 sec. |
| Answer» B. 21 to 30 sec. | |
| 56. |
A message is made up entirely of characters from the set X = {P,Q,R,S,T}. The table of probabilities for each of the characters is shown below: |
| A. | 125 |
| B. | 225 |
| C. | 525 |
| D. | 121 |
| Answer» C. 525 | |
| 57. |
Station A needs to send a message consisting of 9 packets to Station B using a sliding window (window size 3) and goback-n error control strategy. All packets are ready and immediately available for transmission. If every 5th packet that A transmits gets lost (but no acts from B ever get lost), then what is the number of packets that A will transmit for sending the message to B? |
| A. | 12 |
| B. | 14 |
| C. | 16 |
| D. | 18 |
| Answer» D. 18 | |
| 58. |
In a token ring network, the transmission speed is 10 |
| A. | 500 m of cable |
| B. | 200 m of cable |
| C. | 20 m of cable |
| D. | 50 m of cable |
| Answer» D. 50 m of cable | |
| 59. |
How many 8-bit characters can be transmitted per second over a 9600 baud serial communication link using asynchronous mode of transmission with one start bit, eight data bits, two stop bits and one parity bit? |
| A. | 600 |
| B. | 800 |
| C. | 876 |
| D. | 1200 |
| Answer» C. 876 | |
| 60. |
Consider two hosts X and Y, connected by a single direct link of rate 10 |
| A. | p = 50 and q = 100 |
| B. | p = 50 and q = 400 |
| C. | p = 100 and q = 50 |
| D. | p = 400 and q = 50 |
| Answer» E. | |
| 61. |
Consider a binary code that consists of only four valid codewords as given below : |
| A. | p = 3 and q = 1 |
| B. | p = 3 and q = 2 |
| C. | p = 4 and q = 1 |
| D. | p = 4 and q = 2 |
| Answer» C. p = 4 and q = 1 | |
| 62. |
Suppose computers A and B have IP addresses 10.105.1.113 and 10.105.1.91 respectively and they both use the same net mask N. Which of the values of N given below should not be used, if A and B should belong to the same network? |
| A. | 255.255.255.0 |
| B. | 255.255.255.128 |
| C. | 255.255.255.192 |
| D. | 255.255.255.244 |
| Answer» E. | |
| 63. |
An Internet Service Provider (ISP) has the following chunk of CIDR-based IP addresses available with it; 245.248. 128.0/ 20. The ISP wants to give half of this chunk of addresses to organization A and a quarter to organization B, while retaining the remaining with itself. Which of the following is a valid allocation of addresses to A to B? |
| A. | 245.248. 136.0/21 and 245.248. 128.0/022 |
| B. | 245.248. 128.0/21 and 245.248. 128.0/22 |
| C. | 245.248. 132.0/22 and 245.248. 132.0/21 |
| D. | 245.248. 136.0/24 and 245.248. 132.0/21 |
| Answer» B. 245.248. 128.0/21 and 245.248. 128.0/22 | |
| 64. |
Host A sends a UDP datagram containing 8880 bytes of user data to host B over an Ethernet LAN. Ethernet frames may carry data up to 1500 bytes (i.e. MTU = 1500 bytes).Size of UDP header is 8 bytes and size of IP header is 20 bytes. There is no option field in IP header. How many total number of IP fragments will be transmitted and what will be the contents of offset field in the last fragment? |
| A. | 6 and 925 |
| B. | 6 and 7400 |
| C. | 7 and 1110 |
| D. | 7 and 8880 |
| Answer» D. 7 and 8880 | |
| 65. |
A computer on a 10 Mbps network is regulated by a token bucket. The token bucket is filled at a rate of 2 Mbps. It is initially filled to capacity with 16 Megabits. What is the maximum duration for which the computer can transmit at the full 10 Mbps? |
| A. | 1.6 s |
| B. | 2 s |
| C. | 5 s |
| D. | 8 s |
| Answer» C. 5 s | |
| 66. |
Consider a source computer (S) transmitting a file of size 106 bit to a destination computer (D) over a network of two routers (R |
| A. | 1005 ms |
| B. | 1010 ms |
| C. | 3000 ms |
| D. | 3003 ms |
| Answer» B. 1010 ms | |
| 67. |
The cost of link N2 -N3 reduces to 2 in (both directions). After the next round of updates, what will be the new distance vector at node N3? |
| A. | 3, 2, 0, 2, 5 |
| B. | 3, 2, 0, 2, 6 |
| C. | 7, 2, 0, 2, 5 |
| D. | 7, 2, 0, 2, 6 |
| Answer» B. 3, 2, 0, 2, 6 | |
| 68. |
Suppose the weights of all unused links in the previous question are changed to 2 and the distance vector algorithm is used again until all routing tables stabilize. How many links will now remain unused? |
| A. | 0 |
| B. | 1 |
| C. | 2 |
| D. | 3 |
| Answer» C. 2 | |
| 69. |
An IP machine Q has a path to another IP machine H via three IP routers R1, R2, and R3. |
| A. | Only I1 and I2 |
| B. | Only I1 |
| C. | Only I2 and I3 |
| D. | Only I3 and I4 |
| Answer» D. Only I3 and I4 | |
| 70. |
Host A (on TCP/IP v4 network A) sends an IP datagram D to host B (also on TCP/IP v4 network B). Assume that no error occurred during the transmission of D. When D reaches B, which of the following IP header field(s) may be different from that of the original datagram D? |
| A. | (i) only |
| B. | (i) and (ii) only |
| C. | (ii) and (iii) only |
| D. | (i), (ii) and (iii) |
| Answer» E. | |
| 71. |
In the network 200.10.11.144/27, the fourth octet (in decimal) of the last IP address of the network which can be assigned to a host is ______. |
| A. | 200.10.11.158. |
| B. | 500.10.11.155. |
| C. | 300.18.11.158. |
| D. | 20.100.11.158. |
| Answer» B. 500.10.11.155. | |
| 72. |
In a packet switching network, packets are routed from source to destination along a single path having two intermediate nodes. If the message size is 24 byte and each packet contains a header of 3 byte, then the optimum packet size is |
| A. | 4 |
| B. | 6 |
| C. | 7 |
| D. | 9 |
| Answer» E. | |
| 73. |
While opening a TCP connection, the initial sequence number is to be derived using a time-of-day (ToD) clock that keeps running even when the host is down. The low order 32 bits of the counter of the ToD clock is to be used for the initial sequence numbers. The clock counter increments once per millisecond. The maximum packet lifetime is given to be 64s. Which one of the choices given below is closest to the minimum permissible rate at which sequence numbers used for packets of a connection can increase? |
| A. | 0.015/s |
| B. | 0.064/s |
| C. | 0.135/s |
| D. | 0.327/s |
| Answer» B. 0.064/s | |
| 74. |
One of the header fields in an IP datagram is the Time To Live (TTL) field. Which of the following statements best explains the need for the field? |
| A. | It can be used to prioritize packets |
| B. | It can be used to reduce delays |
| C. | It can be used to optimize throughput |
| D. | It can be used to prevent packet looping |
| Answer» E. | |
| 75. |
The transport layer protocols used for real time multimedia, file transfer, DNS and e-mail, respectively are |
| A. | TCP, UDP, UDP and TCP |
| B. | UDP, TCP, TCP and UDP |
| C. | UDP, TCP, UDP and TCP |
| D. | TCP, UDP, TCP and UDP |
| Answer» D. TCP, UDP, TCP and UDP | |
| 76. |
Which one of the following is TRUE about the interior gateway routing protocols - Routing Information Protocol (RIP) and Open Shortest Path First (OSPF)? |
| A. | RIP uses distance vector routing and OSPF uses link state routing |
| B. | OSPF uses distance vector routing and RIP uses link state routing |
| C. | Both RIP and OSPF use link state routing |
| D. | Both RIP and OSPF use distance vector routing |
| Answer» B. OSPF uses distance vector routing and RIP uses link state routing | |
| 77. |
A and B are the only two stations on an Ethernet. Each has a steady queue of frames to send. Both A and B attempt to transmit a frame, collide, and A wins the first backoff race. At the end of this successful transmission by A, both A and B attempt to transmit and collide. The probability that A wins the second backoff race is |
| A. | 0.5 |
| B. | 0.625 |
| C. | 0.75 |
| D. | 1.0 |
| Answer» C. 0.75 | |
| 78. |
Suppose the round trip propagation delay for a 10 Mbps Ethernet having 48 bit jamming signal is 46.4 ms. The minimum frame size is |
| A. | 94 |
| B. | 416 |
| C. | 464 |
| D. | 512 |
| Answer» E. | |
| 79. |
A client process P needs to make a TCP connection to a server process S. Consider the following situation. The server process S executes a socket (), a bind () and a listen () system call in that order, following which it is preempted. Subsequently, the client process P executes a socket () system call followed by connect () system call to connect to the server process S. The server process has not executed any accept () system call. Which one of the following events could take place? |
| A. | Connect () system call returns successfully |
| B. | Connect () system call blocks |
| C. | Connect () system call returns an error |
| D. | Connect () system call returns in a core dump |
| Answer» D. Connect () system call returns in a core dump | |
| 80. |
The maximum number of IPv4 router addresses that can be listed in the record route (RR) option field of an IPv4 header is _________. |
| A. | 99 |
| B. | 9 |
| C. | 999 |
| D. | 91 |
| Answer» C. 999 | |
| 81. |
Consider the following statements about the routing protocols. Routing Information Protocol (RIP) and Open Shortest Path First (OSPF) in an IPv4 network. |
| A. | I and IV only |
| B. | I, II and III only |
| C. | I, II and IV only |
| D. | II, III and IV only |
| Answer» D. II, III and IV only | |
| 82. |
All the routers use the distance vector based routing algorithm to update their routing tables. Each router starts with its routing table initialized to contain an entry for each neighbour with the weight of the respective connecting link. After all the routing tables stabilize, how many links in the network will never be used for carrying any data? |
| A. | 4 |
| B. | 3 |
| C. | 2 |
| D. | 1 |
| Answer» D. 1 | |
| 83. |
Consider socket API on a Linux machine that supports connected UDP sockets. A connected UDP socket is a UDP socket on which connect function has already been called. Which of the following statements is/are CORRECT? |
| A. | I only |
| B. | II only |
| C. | Both I and II |
| D. | Neither I nor II |
| Answer» C. Both I and II | |
| 84. |
The values of parameters for the Stop-and-Wait ARQ protocol are as given below : |
| A. | 66.33% |
| B. | 89.33% |
| C. | 39.33% |
| D. | 59.33% |
| Answer» C. 39.33% | |
| 85. |
Suppose two hosts use a TCP connection to transfer a large file. Which of the following statements is/are FALSE with respect to the TCP connection? |
| A. | III only |
| B. | I and III only |
| C. | I and IV only |
| D. | II and IV only |
| Answer» C. I and IV only | |
| 86. |
Identify the correct sequence in which the following packets are transmitted on the network by a host when a browser requests a web page from a remote server, assuming that the host has just been restarted. |
| A. | HTTP GET request, DNS query, TCP SYN |
| B. | DNS query, HTTP GET request, TCP SYN |
| C. | DNS query, TCP SYN, HTTP GET request |
| D. | TCP SYN, DNS query, HTTP GET request |
| Answer» D. TCP SYN, DNS query, HTTP GET request | |
| 87. |
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. | 13 |
| B. | 31 |
| C. | 11 |
| D. | 33 |
| Answer» B. 31 | |
| 88. |
Consider a TCP client and a TCP server running on two different machines. After completing data transfer, the TCP client calls close to terminate the connection and a FIN segment is sent to the TCP server. Server-side TCP responds by sending an ACK which is received by the client-side TCP. As per the TCP connection state diagram (RFC 793), in which state does the client-side TCP connection wait for the FIN from the server-side TCP? |
| A. | LAST-ACK |
| B. | TIME-WAIT |
| C. | FIN-WAIT-1 |
| D. | FIN-WAIT-2 |
| Answer» E. | |
| 89. |
After the update in the previous question, the link N1 -N2 goes down. N2 will reflect this change immediately in its distance vector as cost . After the next round of update, what will be the cost to N1 in the distance vector of N3? |
| A. | 3 |
| B. | 9 |
| C. | 10 |
| D. | |
| Answer» D. | |
| 90. |
Suppose that the stop-and-wait protocol is used on a link with a bit rate of 64 kilobits per second and 20 milliseconds propagation delay. Assume that the transmission time for the acknowledgement and the processing time at nodes are negligible. Then the minimum frame size in bytes to achieve a link utilization of at least 50% is _________. |
| A. | 220 bytes |
| B. | 120 bytes |
| C. | 320 bytes |
| D. | None of the above |
| Answer» D. None of the above | |
| 91. |
Two hosts are connected via a packet switch with 10 |
| A. | 175 |
| B. | 75 |
| C. | 100 |
| D. | 125 |
| Answer» B. 75 | |
| 92. |
A link has a transmission speed of 10 |
| A. | 10ms |
| B. | 12 ms |
| C. | 15ms |
| D. | 2 ms |
| Answer» C. 15ms | |
| 93. |
In a RSA cryptosystem, a participant A uses two prime numbers p = 13 and q =17 to generate her public and private keys. If the public key of A is 35, then the private key of A is ________. |
| A. | 21 |
| B. | 11 |
| C. | 31 |
| D. | 121 |
| Answer» C. 31 | |
| 94. |
A computer network uses polynomials over GF(2) for error checking with 8 bits as information bits and uses x |
| A. | 01011011010 |
| B. | 01011011011 |
| C. | 01011011101 |
| D. | 01011011100 |
| Answer» D. 01011011100 | |
| 95. |
Consider a 128 10 |
| A. | 10 |
| B. | 8 |
| C. | 4 |
| D. | 12 |
| Answer» D. 12 | |
| 96. |
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 8Kbps. The one-way propagation delay is100 milliseconds. Assuming no frame is lost, the sender throughput is ________ bytes/second. |
| A. | 1.5 Kbps |
| B. | 2.5 Kbps |
| C. | 12.5 Kbps |
| D. | 20.5 Kbps |
| Answer» C. 12.5 Kbps | |
| 97. |
Identify the correct order in which the following actions take place in an interaction between a web browser and a web server. |
| A. | 4, 2, 1, 3 |
| B. | 1, 2, 3, 4 |
| C. | 4, 1, 2, 3 |
| D. | 2, 4, 3 , 1 |
| Answer» B. 1, 2, 3, 4 | |
| 98. |
Suppose that the sliding window protocol is used with the sender window size of 2 |
| A. | 16 ms |
| B. | 18 ms |
| C. | 20 ms |
| D. | 22 ms |
| Answer» C. 20 ms | |
| 99. |
What is the minimum number of bits l that will be required to represent the sequence numbers distinctly? Assume that no time gap need to be given between transmission of two frames. |
| A. | I = 2 |
| B. | I = 3 |
| C. | I = 4 |
| D. | I = 5 |
| Answer» E. | |
| 100. |
In serial data transmission, every byte of data is padded with a 0 in the beginning and one or two 1 s at the end of byte because |
| A. | receiver is to be synchronized for byte reception |
| B. | receiver recovers lost 0s and 1s from these padded bits |
| C. | padded bits are useful in parity computation |
| D. | None of the above |
| Answer» B. receiver recovers lost 0s and 1s from these padded bits | |