Shaping and Policing Concepts 421

Q&A

As mentioned in the Introduction, you have two choices for review questions. The questions that follow next give you a more difficult challenge than the exam itself by using an open-ended question format. By reviewing now with this more difficult question format, you can exercise your memory better, and prove your conceptual and factual knowledge of this chapter. You can find the answers to these questions in Appendix A.

The second option for practice questions is to use the CD included with this book. It includes a testing engine and more than 200 multiple-choice questions. You should use this CD nearer to the end of your preparation, for practice with the actual exam format. You can even customize the CD exam to include, or not include, the topics that are only on the CCIP QoS.

Shaping and Policing Concepts

1Explain the points during the process of a single router receiving and forwarding traffic at which shaping and policing can be enabled on a router.

2Compare and contrast the actions that shaping and policing take when a packet exceeds a traffic contract.

3Compare and contrast the effects that shaping and policing have on bandwidth, delay, jitter, and loss.

4Describe the typical locations to enable shaping and policing in an internetwork.

5Describe the reasons behind egress blocking in a Frame Relay network with a T1 access link at the main site, 128-kbps access links at each of 20 remote sites, with 64-kbps CIR VCs from the main site to each remote site.

6If a router has a shaping tool configured, with a shaping rate of 256 kbps, and a Bc of 16,000 bits, what Tc value does the shaping tool use?

7If a router has a shaping tool configured, with a shaping rate of 512 kbps, and a Be of 16,000 bits, what Tc value does the shaping tool use?

8Define the terms Tc, Bc, Be, and CIR.

9Explain the goal of the Da and Dc debt processes when using CAR.

10Describe the concept of traffic-shaping adaption, explaining the two triggers that cause shaping to adapt.

11Describe the difference between interface output queues and shaping queues, and explain where the queues could exist on a router with 1 physical interface and 20 subinterfaces.

Traffic-Policing Tools 423

22DTS has been configured under subinterface s0/0.1. What show command lists statistics for DTS behavior just for that subinterface?

23CB shaping has been configured under subinterface s0/0.1. What show command lists statistics for CB shaping behavior just for that subinterface?

24FRTS has been configured under subinterface s0/0.1. What show command lists statistics for FRTS behavior just for that subinterface?

25Which of the traffic-shaping tools can be enabled on PPP interfaces?

26Which of the traffic-shaping tools can be enabled on each VC on a Frame Relay multipoint subinterface?

27Which of the traffic-shaping tools support adaptive shaping?

28For which of the traffic-shaping tools does IOS perform shaping processing on 7500 VIP cards?

29Which of the traffic-shaping tools can classify traffic to shape subsets of the traffic on a subinterface?

30Which shaping tools do not support WFQ and PQ to be used for the shaping queues?

31Which shaping tools do not allow WFQ or LLQ to be used for the interface output queuing at the same time as the shaping tool is enabled on the same interface?

Traffic-Policing Tools

32List the command, with the correct syntax, that sets a policed rate of 512 kbps, a Bc of 1 second’s worth of traffic, and a Be of an additional 0.5 second’s worth of traffic, when using CAR. Do not assume any defaults; explicitly set the values in the command. You can choose any other settings needed for the command.

33Explain the use of the continue keyword as part of CAR policing actions, and the feature CAR provides through the keyword.

34Which policing tools allow for three categories of actions to take?

35Explain the concept behind re-marking policed packets versus discarding the packets.

36CAR has been configured under subinterface s0/0.1. What show command lists statistics for CAR behavior just for that subinterface?

37CB policing has been configured under subinterface s0/0.1. What show command lists statistics for CB policing behavior just for that subinterface?

This chapter covers the following exam topics specific to the DQOS and QoS exams:

DQOS Exam Topics

•Explain how TCP responds to congestion.

•Explain tail drop and global synchronization.

•Identify and differentiate between the following Cisco IOS Software congestionavoidance tools: RED, WRED, and FRED.

•Configure Cisco IOS Software congestion-avoidance features.

QoS Exam Objectives

•Describe Random Early Detection (RED).

•Describe the Weighted Random Early Detection (WRED) mechanism.

•Configure Weighted Random Early Detection (WRED) on Cisco routers.

•Describe the Flow-based WRED mechanism.