Q.1 What is the main purpose of flow control in computer networks?
To prevent network congestion by controlling packet loss
To regulate data transmission between sender and receiver to prevent overwhelming
To prioritize certain packets over others
To encrypt data during transmission
Explanation - Flow control ensures that the sender does not send data faster than the receiver can process, avoiding data loss at the receiving end.
Correct answer is: To regulate data transmission between sender and receiver to prevent overwhelming
Q.2 Which protocol uses sliding window mechanism for flow control?
UDP
TCP
IP
ICMP
Explanation - TCP uses a sliding window mechanism to control the amount of data that can be sent before receiving an acknowledgment from the receiver.
Correct answer is: TCP
Q.3 Which type of congestion control is implemented at the network layer?
End-to-End Congestion Control
Link Layer Congestion Control
Transport Layer Congestion Control
Application Layer Congestion Control
Explanation - End-to-end congestion control operates at the transport layer and relies on feedback from the receiver to prevent congestion.
Correct answer is: End-to-End Congestion Control
Q.4 Which of the following is NOT a symptom of network congestion?
High packet loss
Increased delay
Low throughput
Encryption failure
Explanation - Encryption failure is unrelated to network congestion. Congestion manifests as high packet loss, increased delay, and low throughput.
Correct answer is: Encryption failure
Q.5 Which flow control technique uses 'stop-and-wait' method?
TCP sliding window
UDP streaming
Stop-and-Wait protocol
Go-Back-N ARQ
Explanation - In stop-and-wait flow control, the sender sends one frame and waits for an acknowledgment before sending the next frame.
Correct answer is: Stop-and-Wait protocol
Q.6 Which congestion control algorithm reduces the transmission rate upon detecting packet loss?
Leaky bucket
Slow start
Additive Increase Multiplicative Decrease (AIMD)
Sliding window
Explanation - AIMD increases the transmission rate gradually and reduces it multiplicatively upon detecting packet loss to control congestion.
Correct answer is: Additive Increase Multiplicative Decrease (AIMD)
Q.7 What is the main difference between flow control and congestion control?
Flow control works on the sender side; congestion control works on the receiver side
Flow control prevents overwhelming the receiver; congestion control prevents network congestion
Flow control uses sliding window; congestion control uses stop-and-wait
There is no difference; they are the same
Explanation - Flow control regulates data rate between sender and receiver, while congestion control manages traffic load in the network to prevent congestion.
Correct answer is: Flow control prevents overwhelming the receiver; congestion control prevents network congestion
Q.8 Which of the following is a proactive congestion control mechanism?
Random Early Detection (RED)
TCP Slow Start
Stop-and-Wait
Go-Back-N
Explanation - RED detects potential congestion early by probabilistically dropping packets before the queue becomes full, preventing congestion proactively.
Correct answer is: Random Early Detection (RED)
Q.9 Which of these is a reactive congestion control method?
Leaky bucket
Explicit Congestion Notification (ECN)
TCP Tahoe
Random Early Detection (RED)
Explanation - TCP Tahoe reacts to congestion by reducing the congestion window when packet loss is detected, making it a reactive method.
Correct answer is: TCP Tahoe
Q.10 In TCP congestion control, what is the purpose of the 'slow start' phase?
To gradually increase congestion window to probe network capacity
To immediately use full bandwidth available
To avoid using network for initial packets
To encrypt TCP packets
Explanation - The slow start phase begins with a small congestion window and increases it exponentially to find the network's capacity without causing congestion.
Correct answer is: To gradually increase congestion window to probe network capacity
Q.11 Which flow control mechanism is commonly used in UDP?
Sliding Window
Stop-and-Wait
UDP does not provide flow control
TCP Congestion Window
Explanation - UDP is connectionless and does not implement any flow control; it sends packets at the application-specified rate.
Correct answer is: UDP does not provide flow control
Q.12 What is the main function of the 'leaky bucket' algorithm?
To provide encryption for data
To control data transmission rate and smooth bursty traffic
To detect network failures
To increase network throughput beyond capacity
Explanation - The leaky bucket algorithm controls the rate at which data is sent into the network, smoothing bursts to prevent congestion.
Correct answer is: To control data transmission rate and smooth bursty traffic
Q.13 Which of the following can help reduce congestion in a network?
Increasing packet size
Traffic shaping and flow control
Disabling acknowledgments
Using UDP only
Explanation - Traffic shaping and flow control regulate the flow of data into the network, helping to prevent congestion and packet loss.
Correct answer is: Traffic shaping and flow control
Q.14 Which metric is commonly used to detect congestion in a network?
Queue length at routers
IP address type
Packet encryption method
MAC address
Explanation - High queue lengths in routers indicate potential congestion, prompting congestion control mechanisms to act.
Correct answer is: Queue length at routers
Q.15 Which protocol provides explicit feedback from the network to indicate congestion?
TCP with ECN
UDP
ICMP
HTTP
Explanation - Explicit Congestion Notification (ECN) allows network devices to mark packets to indicate congestion without dropping them, enabling TCP to react.
Correct answer is: TCP with ECN
Q.16 What happens in TCP when duplicate ACKs are received?
Congestion window is increased
Fast retransmit is triggered
Data transmission stops permanently
Packets are encrypted
Explanation - When TCP receives duplicate acknowledgments, it assumes packet loss and retransmits the missing packet without waiting for timeout (fast retransmit).
Correct answer is: Fast retransmit is triggered
Q.17 Which flow control method uses buffer size to limit sender's data rate?
Sliding window
Stop-and-Wait
Leaky bucket
UDP streaming
Explanation - Sliding window flow control uses the receiver's buffer size to determine how many packets the sender can transmit before receiving acknowledgment.
Correct answer is: Sliding window
Q.18 Which technique is used to prevent congestion collapse?
Reducing data rate upon congestion
Using fixed packet sizes
Encrypting packets
Switching to UDP only
Explanation - Reducing the data transmission rate when congestion is detected prevents network congestion from worsening, avoiding congestion collapse.
Correct answer is: Reducing data rate upon congestion
Q.19 Which TCP algorithm uses additive increase and multiplicative decrease?
TCP Reno
TCP Tahoe
AIMD
Stop-and-Wait
Explanation - AIMD (Additive Increase Multiplicative Decrease) is a congestion control algorithm that gradually increases the sending rate and reduces it sharply upon detecting congestion.
Correct answer is: AIMD
Q.20 Which of the following is true about congestion avoidance in TCP?
It increases the congestion window exponentially throughout
It stops data transmission permanently on packet loss
It gradually increases the congestion window to probe available bandwidth
It ignores network feedback
Explanation - Congestion avoidance gradually increases the congestion window to find optimal throughput without causing congestion.
Correct answer is: It gradually increases the congestion window to probe available bandwidth
Q.21 What is the primary goal of the token bucket algorithm?
To encrypt TCP packets
To control average transmission rate and allow bursts
To detect network failures
To avoid IP fragmentation
Explanation - The token bucket algorithm controls the long-term transmission rate while allowing short-term bursts of data, smoothing traffic and preventing congestion.
Correct answer is: To control average transmission rate and allow bursts
Q.22 Which of the following reduces the likelihood of congestion in high-speed networks?
Flow control and traffic shaping
Increasing packet size
Using stop-and-wait protocol
Ignoring acknowledgments
Explanation - Flow control and traffic shaping manage the rate of data entering the network, preventing bottlenecks and congestion in high-speed networks.
Correct answer is: Flow control and traffic shaping
Q.23 Which layer primarily implements congestion control?
Transport layer
Network layer
Data link layer
Application layer
Explanation - Congestion control is mainly handled by the transport layer, as it monitors and adjusts the rate of data transmission to avoid network congestion.
Correct answer is: Transport layer
Q.24 What does 'fast recovery' in TCP aim to do?
Immediately stop data transmission
Recover quickly from packet loss without going to slow start
Encrypt the lost packets
Switch to UDP for faster transmission
Explanation - Fast recovery in TCP avoids dropping the congestion window to 1 after a packet loss, allowing faster recovery than restarting from slow start.
Correct answer is: Recover quickly from packet loss without going to slow start