CCIP Quality of Service (QoS) : 642-642 Exam
Exam Number/Code: 642-642
Exam Name: CCIP Quality of Service (QoS)
“Quality of Service (QoS)”, also known as 642-642 exam, is a Cisco certification.
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642-642 QOS
Quality of Service Exam
Exam Number: 642-642
Associated Certifications: CCIP, CCVP, IP Telephony Design Specialist, IP Telephony Express Specialist, IP Telephony Operations Specialist, and IP Telephony Support Specialist
Duration: 90 minutes (45-55 questions)
Available Languages: English
Click Here to Register: Pearson VUE
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Exam Description Exam Topics Recommended Training Additional Resources
Exam Description
The QOS exam is one of the qualifying exams for the Cisco Certified Internetwork Professional, Cisco Certified Voice Professional, Cisco IP Telephony Design Specialist, Cisco IP Telephony Express Specialist, Cisco IP Telephony Operations Specialist, and Cisco IP Telephony Support Specialist certifications. The QOS 642-642 exam will test materials covered under the Implementing Cisco Quality of Service QOS v2.1 course. The exam will certify that the successful candidate has knowledge and skills necessary to configure and troubleshoot Cisco IOS routers running Quality of Service protocols in Service Provider and Enterprise environments. The exam covers topics on IP QOS, classification and marking Mechanisms, queuing mechanisms, traffic shaping and policing mechanisms, congestion avoidance mechanisms, link efficiency mechanisms, modular QOS command line interface, and QOS Best Practices.
Exam Topics
The following information provides general guidelines for the content likely to be included on the exam. However, other related topics may also appear on any specific delivery of the exam.
IP QoS Fundamentals
Given a description of a converged network, identify problems that could lead to poor quality of service and explain how the problems might be resolved
Define the term Quality of Service (QoS) and identify and explain the key steps to implementing QoS on a converged network
IP QoS Components
List and explain the models for providing Quality of Service on a network
Explain the purpose and function of the DiffServ model
Describe the basic format of and explain the purpose of the DSCP field in the IP header
Define and explain the different per hop behaviors used in DSCP
Explain the interoperability between DSCP-based and IP-precedence-based devices in a network
Given a list of QoS actions, correctly match the QoS actions to mechanisms for implementing QoS and identify where in a network the different QoS mechanisms are commonly used
Modular QoS CLI and Auto-QoS
Given a network requiring QoS, explain how to implement a QoS policy using MQC
Explain how AutoQoS is used to implement QoS policy
Classification and Marking
Explain how link layer and network layer markings are used to define service classes and the different applications represented by each of these service classes
Given a network and a description of QoS issues, use MQC CLI commands to classify packets
Given a network and a description of QoS issues, use class-based marking to assign packets to a specific service class
Describe the function of Network Based Application Recognition
Describe the purpose of pre-classification to support QoS in various VPN (IPSEC, GRE, L2TP) configurations
Describe QoS trust boundaries and their significance in LAN based classification and marking
Identify the different classification and marking options available on Cisco L2 and L3 switching platforms
Congestion Management Methods
List and explain the different queuing algorithms
Explain the components of hardware and software queuing systems on Cisco routers and how they are effected by tuning and congestion
Describe the benefits and drawbacks of using WFQ to implement QoS
Explain the purpose and features of Class-Based WFQ (CBWFQ)
Explain the purpose and features of Low Latency Queuing (LLQ)
Identify the Cisco IOS commands required to configure and monitor LLQ on a Cisco router
Describe and explain the different queuing capabilities available on the Cisco Catalyst 2950 Switch
Congestion Avoidance Methods
Describe the drawbacks tail drop as a congestion control mechanism
Describe the elements of a RED traffic profile
Describe Weighted Random Early Detection and how it can be used to prevent congestion
Identify the Cisco IOS commands required to configure and monitor DSCP-based CB-WRED
Explain how ECN interacts with WRED in Cisco IOS
Traffic Policing and Shaping
Describe the purpose of traffic conditioning using traffic policing and traffic shaping and differentiate between the features of each
Explain how network devices measure traffic rates using single rate or dual rate, single or dual token bucket mathematical models
Identify the Cisco IOS commands required to configure and monitor single rate and dual rate CB-Policing
Identify the Cisco IOS commands required to configure and monitor percentage based CB-Policing
Explain how the two rate limits, average rate and peak rate, can be used to rate limit traffic
Identify the Cisco IOS commands required to configure and monitor CB-Shaping
Identify the Cisco IOS commands required to configure and monitor Frame Relay adaptive CB-Shaping on Frame Relay interfaces
Link Efficiency Mechanisms
Explain the various link efficiency mechanisms and their function
Identify the Cisco IOS commands required to configure and monitor CB header compression
Given a list of link speeds and a specific delay requirement, determine the proper fragment size to use at each link speed and identify the typical delay requirement for VoIP packets
Identify the Cisco IOS commands required to configure and monitor Multilink PPP with Interleaving
Identify the Cisco IOS commands required to configure and monitor FRF.12
QoS Best Practices
Explain the QoS requirements of the different application types
List typical enterprise traffic classes then identify the delay, jitter, packet loss and bandwidth requirements of each traffic class
Explain the best practice QoS implementations and configurations within the campus LAN
Explain the best practice QoS implementations and configurations on the WAN customer edge (CE) and provider edge (PE) routers
QUESTION 27:
Which of the following statements are valid when considering the need for link
efficiency tools such as fragmentation and compression? (Choose all that apply.)
A. Fragmentation allows voice CAC mechanism to increase call volume.
B. While adding bandwidth to counter congestion, reducing load on a link by
compression increases available bandwidth.
C. Variable sized packets create extra processing overhead for most IOS queuing
mechanism, but fragmentation creates uniformity, thus decreasing queuing delay.
D. Based on link speed, some single packets are large enough that their serialization
delay causes intolerable delay for voice or video.
E. All of the above.
Answer: B, D
QUESTION 28:
You are the network administrator at Certkiller . The newly appointed Certkiller
trainee wants to know in which configuration mode the following MQC command
can be used. What will your reply be?
match ip dscp af41?
A. interface configuration mode
B. service policy configuration mode
C. class map configuration mode
D. policy map configuration mode
E. none of the above
Answer: C
Explanation:
Router(config-cmap)#match ip dscp dscp [dcscp ...]
1) Select up to eight DSCP values or names
2) All packets marked with one of the selected DSCP values are matched by
this class map.
Reference: Introduction to IP QoS (course) p.8-21
QUESTION 29:
What is a key benefit of using the Cisco Modular QoS Command Line Interface
(MQC)?
A. Provides performance metrics for QoS configurations.
B. Eliminates the need for map classes to perform traffic classification.
C. Allows users to specify traffic classes independently from QoS polices.
D. Allows QoS policy information to be automatically distributed throughout the
network.
E. Provides an integrated testing mechanism for traffic classification and QoS policy
configurations.
Answer: C
Testinside CCIP 642-642 Questions and Answers : 182 Q&As
Updated: October 15th , 2008
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