NUST NET Engineering Test computer science: Data Communication MCQs

Practice Data Communication MCQs for NUST NET Engineering Test computer science — topic-wise sets with solved answers.

NUST NET Engineering Test computer science: Data Communication MCQs — sample questions

  1. Question 1

    Q1. What is the primary function of the Physical Layer in the OSI model?

    • A) Routing
    • B) Error detection
    • C) Transmission of raw bits
    • D) Flow control

    Answer: Transmission of raw bits

    Explanation: The Physical Layer is responsible for transmitting raw bits over a physical medium, defining electrical and mechanical specifications.

  2. Question 2

    Q2. Which protocol is used for error detection in Data Link Layer?

    • A) TCP
    • B) UDP
    • C) CRC
    • D) HTTP

    Answer: CRC

    Explanation: Cyclic Redundancy Check (CRC) is used for error detection in Data Link Layer by calculating a checksum for data frames.

  3. Question 3

    Q3. What is the maximum data rate of a noiseless channel with a bandwidth of 3000 Hz?

    • A) 6000 bps
    • B) 3000 bps
    • C) 12000 bps
    • D) 9000 bps

    Answer: 6000 bps

    Explanation: Using Nyquist's theorem, maximum data rate = 2 * bandwidth * log2(L), for binary (L=2), it simplifies to 2 * 3000 = 6000 bps.

  4. Question 4

    Q4. In a CSMA/CD network, what happens when a collision occurs?

    • A) The station waits for a random time
    • B) The station retransmits immediately
    • C) The station aborts transmission
    • D) The station sends a jam signal

    Answer: The station sends a jam signal

    Explanation: When a collision is detected, the station sends a jam signal to notify other stations, then waits for a random time before retransmitting.

  5. Question 5

    Q5. What is the purpose of the Time To Live (TTL) field in an IP packet?

    • A) To ensure packet delivery
    • B) To prevent packet looping
    • C) To prioritize packets
    • D) To fragment packets

    Answer: To prevent packet looping

    Explanation: TTL is used to limit the lifetime of a packet, preventing it from looping indefinitely in the network.

  6. Question 6

    Q6. Which of the following is a characteristic of TCP?

    • A) Connectionless
    • B) Best-effort delivery
    • C) Guaranteed delivery
    • D) Stateless

    Answer: Guaranteed delivery

    Explanation: TCP provides guaranteed delivery through acknowledgments and retransmissions, making it a connection-oriented protocol.

  7. Question 7

    Q7. What is the function of the ARP protocol?

    • A) To resolve IP addresses to MAC addresses
    • B) To resolve MAC addresses to IP addresses
    • C) To route packets
    • D) To fragment packets

    Answer: To resolve IP addresses to MAC addresses

    Explanation: ARP is used to resolve IP addresses to MAC addresses, enabling devices to communicate at the Data Link Layer.

  8. Question 8

    Q8. In a Stop-and-Wait protocol, what is the maximum efficiency?

    • A) 1 / (1 + 2a)
    • B) 1 / (1 + a)
    • C) a / (1 + a)
    • D) 1 / a

    Answer: 1 / (1 + 2a)

    Explanation: The efficiency of Stop-and-Wait is given by 1 / (1 + 2a), where a = Tp / Tt, Tp is propagation time and Tt is transmission time.

  9. Question 9

    Q9. What is the purpose of the Nagle's algorithm?

    • A) To improve TCP performance by reducing overhead
    • B) To ensure reliable data transfer
    • C) To prioritize packets
    • D) To fragment packets

    Answer: To improve TCP performance by reducing overhead

    Explanation: Nagle's algorithm reduces overhead by buffering small packets and sending them in a single segment, improving TCP performance.

  10. Question 10

    Q10. Which layer is responsible for routing in the OSI model?

    • A) Physical Layer
    • B) Data Link Layer
    • C) Network Layer
    • D) Transport Layer

    Answer: Network Layer

    Explanation: The Network Layer is responsible for routing packets between devices on different networks.

  11. Question 11

    Q11. What is the primary function of the Session Layer?

    • A) To establish and manage connections
    • B) To route packets
    • C) To provide error detection
    • D) To fragment packets

    Answer: To establish and manage connections

    Explanation: The Session Layer establishes, manages, and terminates connections between applications. NET computer science MCQs often test this core concept.

  12. Question 12

    Q12. In a Go-Back-N protocol, what happens when a packet is lost?

    • A) Only the lost packet is retransmitted
    • B) All packets from the lost packet onwards are retransmitted
    • C) The station waits for a timeout
    • D) The station sends an ACK for the lost packet

    Answer: All packets from the lost packet onwards are retransmitted

    Explanation: In Go-Back-N, when a packet is lost, all packets from the lost packet onwards are retransmitted.

  13. Question 13

    Q13. What is the function of the IGMP protocol?

    • A) To manage multicast group membership
    • B) To resolve IP addresses to MAC addresses
    • C) To route packets
    • D) To fragment packets

    Answer: To manage multicast group membership

    Explanation: IGMP is used to manage multicast group membership, allowing devices to join or leave multicast groups.

  14. Question 14

    Q14. Which of the following is a characteristic of UDP?

    • A) Connection-oriented
    • B) Guaranteed delivery
    • C) Best-effort delivery
    • D) Stateful

    Answer: Best-effort delivery

    Explanation: UDP provides best-effort delivery, meaning it does not guarantee delivery or order of packets.

  15. Question 15

    Q15. What is the purpose of the subnet mask?

    • A) To identify the network ID
    • B) To identify the host ID
    • C) To route packets
    • D) To fragment packets

    Answer: To identify the network ID

    Explanation: The subnet mask is used to determine the network ID and host ID parts of an IP address.

  16. Question 16

    Q16. In a token ring network, what happens when a station receives the token?

    • A) It transmits data
    • B) It waits for a random time
    • C) It sends a jam signal
    • D) It aborts transmission

    Answer: It transmits data

    Explanation: When a station receives the token, it is allowed to transmit data.

  17. Question 17

    Q17. What is the function of the DNS protocol?

    • A) To resolve domain names to IP addresses
    • B) To route packets
    • C) To fragment packets
    • D) To manage multicast group membership

    Answer: To resolve domain names to IP addresses

    Explanation: DNS is used to resolve domain names to IP addresses, enabling devices to communicate using easy-to-remember names.

  18. Question 18

    Q18. Which layer is responsible for providing flow control in the OSI model?

    • A) Data Link Layer
    • B) Transport Layer
    • C) Network Layer
    • D) Session Layer

    Answer: Transport Layer

    Explanation: The Transport Layer is responsible for providing flow control, ensuring that data is transmitted at a rate that the receiver can handle.

  19. Question 19

    Q19. What is the purpose of the ACK flag in TCP?

    • A) To acknowledge received data
    • B) To request retransmission
    • C) To establish a connection
    • D) To terminate a connection

    Answer: To acknowledge received data

    Explanation: The ACK flag is used to acknowledge received data, ensuring reliable data transfer.

  20. Question 20

    Q20. In a sliding window protocol, what is the purpose of the window size?

    • A) To determine the number of packets that can be sent before an ACK is received
    • B) To determine the maximum packet size
    • C) To determine the transmission rate
    • D) To determine the propagation delay

    Answer: To determine the number of packets that can be sent before an ACK is received

    Explanation: The window size determines the number of packets that can be sent before an ACK is received, improving efficiency.

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