This chapter covers the following subjects:
Queuing Overview
Introduction to Queuing
Class-Based Weighted Fair Queuing (CBWFQ)
Low-Latency Queuing (LLQ)
Compression Techniques
The CCNP Remote Access exam requires you to have an in-depth understanding of various WAN technologies. In this chapter, the discussion focuses on some of the advanced queuing techniques offered in Cisco IOS. The latter part of this chapter also discusses compression techniques that are possible from Cisco routers.
There are various opinions on whether queuing is needed in a router, or in a network. Normally, there are ways to justify the need for queuing, and the type of queuing required. This chapter discusses the concepts behind queuing, when to use queuing, and which type of queuing is best for a particular situation.
"Do I Know This Already?" Quiz
The purpose of the "Do I Know This Already?" quiz is to help you decide whether you really need to read the entire chapter. If you already intend to read the entire chapter, you do not necessarily need to answer these questions now.
This ten-question quiz, derived from the major sections in the "Foundation Topics" portion of the chapter, helps you determine how to spend your limited study time.
Table 15-1 outlines the major topics discussed in this chapter and the "Do I Know This Already?" quiz questions that correspond to those topics.
Table 15-1 "Do I Know This Already?" Foundation Topics Section-to-Question Mapping
|
Foundation Topics Section |
Questions Covered in This Section |
|
Queuing Overview |
1–2 |
|
Introduction to Queuing |
3–4 |
|
Class-Based Weighted Fair Queuing |
5–6 |
|
Low-Latency Queuing |
7–8 |
|
Compression Techniques |
9–10 |
CAUTION
The goal of self-assessment is to gauge your mastery of the topics in this chapter. If you do not know the answer to a question or are only partially sure of the answer, you should mark this question wrong for purposes of the self-assessment. Giving yourself credit for an answer you correctly guess skews your self-assessment results and might provide you with a false sense of security.
Which network conditions justify the use of queuing? (Select two.)
High-bandwidth interfaces
Congested interfaces
Low-speed interfaces
LAN interfaces
Underutilized interfaces
Which effects does queuing have on a router? (Select two.)
Increases router performance
Decreases CPU load
Increases CPU load
Increases the bandwidth on an interface
Decreases router performance
Which queuing strategy uses the IP type of service (ToS) bits to help determine egress priority?
First-In, First-Out queuing
Fair Queuing
Weighted Fair Queuing
Priority Queuing
How are packets sequenced when using FIFO queuing?
The shortest packets always go to the front of the queue.
The longest packets always go to the front of the queue.
The packets are sequenced based on when each respective first bit arrives on the egress interface.
The packets are sequenced based on when each packet arrives entirely on the egress interface.
Which Cisco IOS command is used to create a list of packets that match one or more criteria?
class-map
policy-map
service-policy
class-list
Which Cisco IOS command determines how much bandwidth a particular flow should get during congested conditions?
class-map
bandwidth
service-policy
policy
Which Cisco IOS command determines how much bandwidth a particular flow should get at all times?
class-map
bandwidth
service-policy
policy
What is the difference between CBWFQ and LLQ?
There is no difference because they use the same IOS commands.
CBWFQ defines a priority queue that is used at all times whereas LLQ is used only during congestion.
LLQ defines a priority queue that is used at all times whereas CBWFQ is used only during congestion.
CBWFQ has more configuration options than LLQ.
Which of the following compression methods can be used only on point-to-point links? (Select two.)
TCP header compression
Stac
Predictor
MPCC
IP header compression
Which of the following compression methods is Cisco-proprietary?
TCP header compression
Stac
Predictor
MPCC
The answers to the "Do I Know This Already?" quiz are found in Appendix A, "Answers to the 'Do I Know This Already?' Quizzes and Q&A." The suggested choices for your next step are as follows:
6 or fewer overall score—Read the chapter. This includes the "Foundation Topics," "Foundation Summary," and the "Q&A" section.
7 or 8 overall score—Begin with the "Foundation Summary" section and then go to the "Q&A" section.
9 or more overall score—If you want more review of these topics, skip to the "Foundation Summary" section and then go to the "Q&A" section. Otherwise, move to the next chapter.