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Wednesday, April 2, 2014

Congestion Control and Quality of Service - MCQs

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MCQs for Congestion Control and Quality of Service

Topic Outline

  • DATA TRAFFIC
  • CONGESTION
    • Open-Loop Congestion Control
    • Closed-Loop Congestion Control
  • TWO EXAMPLES
    • Congestion Control in TCP
    • Congestion Control in Frame Relay
  • QUALITY OF SERVICE
  • TECHNIQUES TO IMPROVE QoS
  • INTEGRATED SERVICES
  • DIFFERENTIATED SERVICES
  • QoS IN SWITCHED NETWORKS
    • QoS in Frame Relay
    • QoS in ATM

Begin and Good luck!

1. _______ is a flow characteristic that applications can tolerate in different degrees.

  • A)            Reliability
  • B)            Delay
  • C)            Jitter
  • D)            Bandwidth

2. The _______ defines the maximum data rate of the traffic.

  • A)            peak data rate
  • B)            maximum burst size
  • C)            effective bandwidth
  • D)            none of the above

3. In Frame Relay, the _____________ defines an average rate in bits per second.

  • A)            access rate
  • B)            committed burst size
  • C)            committed information rate
  • D)            excess burst size

4. In ________ congestion control, policies are applied to prevent congestion before it happens.

  • A)            open-loop
  • B)            closed-loop
  • C)            either (a) or (b)
  • D)            neither (a) nor (b)

5. In ________ we try to avoid traffic congestion.

  • A)            congestion control
  • B)            quality of service
  • C)            either (a) or (b)
  • D)            both (a) and (b)

6. _________ is a characteristic that a flow needs. Lack of it means losing a packet or acknowledgment, which entails retransmission.

  • A)            Reliability
  • B)            Delay
  • C)            Jitter
  • D)            Bandwidth

7. In a network, after the load reaches the capacity, throughput _______.

  • A)            increases sharply
  • B)            increases proportionally with the load
  • C)            declines sharply
  • D)            declines proportionally with the load

8. In _________ queuing, the packets are assigned to different classes and admitted to different queues. The queues, however, are weighted based on the priority of the queues; higher priority means a higher weight. The system processes packets in each queue in a round-robin fashion with the number of packets selected from each queue based on the corresponding weight.

  • A)            FIFO
  • B)            priority
  • C)            weighted fair
  • D)            none of the above

9. In ATM, the _________ class is a best-effort delivery service that does not guarantee anything.

  • A)            CBR
  • B)            VBR
  • C)            ABR
  • D)           UBR

10. The________ normally refers to the maximum length of time the traffic is generated at the peak rate.

  • A)            peak data rate
  • B)            maximum burst size
  • C)            effective bandwidth
  • D)            none of the above

11. In _______ congestion control, mechanisms are used to alleviate congestion after it happens.

  • A)             open-loop
  • B)             closed-loop
  • C)             either (a) or (b)
  • D)             neither (a) nor (b)

12. _______ happens in any system that involves waiting.

  • A)             Congestion
  • B)             Jamming
  • C)             Error
  • D)             none of the above

13. In the ________ algorithm of TCP, the size of the congestion window increases exponentially until it reaches a threshold.

  • A)             slow-start
  • B)             congestion avoidance
  • C)             congestion detection
  • D)             none of the above

14. In Frame Relay, the user can never exceed the_________.

  • A)             access rate
  • B)             committed burst size
  • C)             committed information rate
  • D)             excess burst size

15. In the ___________ algorithm of TCP, the size of the threshold is dropped to one-half, a multiplicative decrease.

  • A)             slow-start
  • B)             congestion avoidance
  • C)             congestion detection
  • D)             none of the above

16. In _________, when a source makes a reservation, it needs to define a flow specification.

  • A)             Integrated Services
  • B)             Differentiated Services
  • C)             Connectionless
  • D)             Connection-Oriented

17. A _________ traffic model has a data rate that does not change.

  • A)             constant bit rate
  • B)             variable bit rate
  • C)             bursty
  • D)             none of the above

18. ________ is the variation in delay for packets belonging to the same flow.

  • A)             Reliability
  • B)             Delay
  • C)             Jitter
  • D)             Bandwidth

19. A ___________ is a packet sent by a node to the source to inform it of congestion.

  • A)             backpressure
  • B)             choke packet
  • C)             implicit signaling
  • D)             explicit signaling

20. In ATM, the _________ class delivers cells at a minimum rate. If more network capacity is available, this minimum rate can be exceeded.

  • A)             CBR
  • B)             VBR
  • C)             ABR
  • D)             UBR

21. In the ________ traffic model, the rate of the data flow changes in time, with the changes smooth instead of sudden and sharp.

  • A)             constant bit rate
  • B)             variable bit rate
  • C)             bursty
  • D)             none of the above

22. In __________, there is no communication between the congested node or nodes and the source. The source guesses that there is a congestion somewhere in the network from other symptoms.

  • A)             backpressure
  • B)             choke packet
  • C)             implicit signaling
  • D)             explicit signaling

23. In a network, when the load reaches the network capacity, the delay _______.

  • A)             increases sharply
  • B)             decreases sharply
  • C)             remains constant
  • D)             cannot be predicted

24. The technique of ________refers to a congestion control mechanism in which a congested node stops receiving data from the immediate upstream node or nodes.

  • A)             backpressure
  • B)             choke packet
  • C)             implicit signaling
  • D)             explicit signalin

25. In ________ queuing, packets are first assigned to a priority class. Each class has its own queue.

  • A)             FIFO
  • B)             priority
  • C)             weighted fair
  • D)             none of the above

26. In ________, queuing packets wait in a buffer (queue) until the node (router or switch) is ready to process them.

  • A)             FIFO
  • B)             priority
  • C)             weighted fair
  • D)             none of the above

27. Traditionally, ________types of characteristics are attributed to a flow.

  • A)             two
  • B)             three
  • C)             four
  • D)             five

28. In Frame Relay, the ___________ is the maximum number of bits in excess of Bc that a user can send during a predefined time.

  • A)             access rate
  • B)             committed burst size
  • C)             committed information rate
  • D)             excess burst size

29. In a network, when the load is below the capacity of the network, the throughput ______________.

  • A)             increases sharply
  • B)             increases proportionally with the load
  • C)             declines sharply
  • D)             declines proportionally with the load

30. In the __________ method, the signal is included in the packets that carry data.

  • A)             backpressure
  • B)             choke packet
  • C)             implicit signaling
  • D)             explicit signaling

31. In a network, when the load is much less than the capacity of the network, the delay is _________.

  • A)             at a maximum
  • B)             at a minimum
  • C)             constant
  • D)             none of the above

32. Congestion in a network or internetwork occurs because routers and switches have _______.

  • A)             tables
  • B)             queues
  • C)             crosspoints
  • D)             none of the above

33. In _________, we try to create an appropriate environment for the traffic.

  • A)             congestion control
  • B)             quality of service
  • C)             either (a) or (b)
  • D)             both (a) and (b)

34. In Frame Relay, the ________ bit warns the sender of congestion in the network.

  • A)             BECN
  • B)             FECN
  • C)             either (a) or (b)
  • D)             neither (a) nor (b)

35. In Frame Relay, the ________ bit is used to warn the receiver of congestion in the network.

  • A)             BECN
  • B)             FECN
  • C)             either (a) or (b)
  • D)             neither (a) nor (b)

36. The ________ is a function of three values: average data rate, peak data rate, and maximum burst size.

  • A)             peak data rate
  • B)             maximum burst size
  • C)             effective bandwidth
  • D)             none of the above

37. In the _________ algorithm of TCP, the size of the congestion window increases additively until congestion is detected.

  • A)             slow-start
  • B)             congestion avoidance
  • C)             congestion detection
  • D)             none of the above

38. In ATM, the _________ class is divided into two subclasses: real-time (VBR-RT) and non-real-time (VBR-NRT). VBR-RT is designed for those users who need real-time services (such as voice and video transmission) and use compression techniques to create a variable bit rate. VBR-NRT is designed for those users who do not need real-time services but use compression techniques to create a variable bit rate.

  • A)             CBR
  • B)             VBR
  • C)             ABR
  • D)             UBR

39. Traffic ______ are qualitative values that represent a data flow.

  • A)             controls
  • B)             descriptors
  • C)             values
  • D)             none of the above

40. _________ is a class-based QoS model designed for IP.

  • A)             Integrated Services
  • B)             Differentiated Services
  • C)             Connectionless
  • D)             Connection-Oriented

41. In the ______ bucket algorithm, bursty chunks are stored in the bucket and sent out at an average rate.

  • A)             leaky
  • B)             token
  • C)             either (a) or (b)
  • D)             neither (a) nor (b)

42. The _______ bucket algorithm allows idle hosts to accumulate credit for the future in the form of tokens.

  • A)             leaky
  • B)             token
  • C)             either (a) or (b)
  • D)             neither (a) nor (b)

43. In ATM, the _________ class is designed for customers who need real-time audio or video services. The service is similar to that provided by a dedicated line such as a T line.

  • A)             CBR
  • B)             VBR
  • C)             ABR
  • D)             UBR

44. In the ______ traffic model, the data rate changes suddenly in a very short time.

  • A)             constant bit rate
  • B)             variable bit rate
  • C)             bursty
  • D)             none of the above

45. In Frame Relay, a ___________ is the maximum number of bits in a predefined time that the network is committed to transfer without discarding any frame or setting the DE bit.

  • A)             access rate
  • B)             committed burst size
  • C)             committed information rate
  • D)             excess burst size

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