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CCNP Self-Study: Understanding and Implementing Quality of Service in Cisco Multilayer Switched Networks

  • Sample Chapter is provided courtesy of Cisco Press.
  • Date: May 13, 2004.

Chapter Description

This chapter describes how QoS is an integral part of any multilayer switched network deployment. With QoS, you can build a network of predictable behavior for latency, jitter, and packet loss. In addition, QoS mitigates anomalous network behavior and provides for differentiation of traffic flows.

Review Questions

Note: For multiple-choice questions, there may be more than one correct answer.

  1. True or False: You should always apply QoS classification in the access layer and as close to the network device as possible.

  2. True or False: Congestion management includes the RED, WRED, and tail-drop QoS features.

  3. What is the purpose of trust boundaries?

    1. To determine the classification of a packet as a specific location in the network.

    2. To determine where in the network packets are dropped.

    3. To determine where in the network to reclassify packets.

    4. It is an administrative configuration where Layer 2 or Layer 3 priority designations of frames or packets are either accepted or not.

  4. Which QoS mechanism, commonly found on low-speed interfaces, reduces delay and jitter on slower-speed links by breaking up large datagrams and interleaving low-delay traffic packets with the resulting smaller packets?

    1. LFI

    2. IP RTP Priority

    3. queuing and scheduling

  5. Which QoS model requires end-to-end configuration?

    1. LFI

    2. IntServ

    3. DiffServ

    4. Traffic conditioning

  6. In designing a multilayer switched network, you are required to condition traffic on a Catalyst switch such that TCP flows do not achieve more than 10 Mbps out of a 100-Mbps interface. Which of the following methods of traffic conditioning achieves link utilization closest to 10 Mbps?

    1. Shaping

    2. Policing

  7. Which of the following methods of traffic conditioning would you use to limit VoIP traffic?

    1. Shaping

    2. Policing

    Figure 19Figure 10-19 QoS Topology for Questions 8-10

  8. Figure 10-19 illustrates an IP Phone attached to a Catalyst 3550 switch. Consider a situation in which the IP Phone is sending voice packets to another IP Phone with a DSCP value of 46 and a CoS value of 5. If the Catalyst 3550 switch is configured to trust DSCP and is using the default mapping tables, what is the internal DSCP of the frame as it traverses the switch?

    1. 5

    2. 46

    3. 40

    4. 0

  9. With regard to Figure 10-19, consider a situation in which the IP Phone is sending voice packets to another IP Phone with a DSCP value of 46 and a CoS value of 5. If the Catalyst 3550 switch is configured to trust CoS and the switch is using the default mapping tables, what is the internal DSCP of the frame as it traverses the switch?

    1. 5

    2. 46

    3. 40

    4. 0

  10. With regard to Figure 10-19, consider a situation in which the IP Phone is sending voice packets to another IP Phone with a DSCP value of 46 and a CoS value of 5. If the Catalyst 3550 switch is configured to untrusted and the switch is using the default mapping tables, what is the internal DSCP of the frame as it traverses the switch?

    1. 5

    2. 46

    3. 40

    4. 0

    Example 10-13 is for use in questions 11 and 12.

    Example 10-13 Sample Policing Configuration

    (text deleted)
    class-map match-any LIMIT-TCP_File_Sharing
     match access-group 100
     match access-group 101
    policy-map LIMIT_File_Sharing
     class LIMIT-TCP_File_Sharing
      police 1536000 20000 exceed-action drop
    (text deleted)
  11. With regard to Example 10-13, which configuration command is the class action of the policy map?

    1. class LIMIT-TCP_File_Sharing

    2. police 1536000 20000 exceed-action drop

    3. match access-group 101

  12. With regard to Example 10-13, which action is taken for packets that conform to the policing rate?

    1. Transmit

    2. Drop

    3. Mark-down

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