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Quality of Service Exam(QOS 642-642)

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Quality of Service Exam (QOS 642-642)

Exam Number: 642-642 Associated Certifications: CCIP, 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 or Prometric

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 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 v2.0 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

Recommended Training

Implementing Cisco Quality of Service ( QOS ) is the recommended training for this exam.

Courses listed are offered by Cisco Learning Partners, the only authorized source for Cisco IT training delivered exclusively by Certified Cisco Instructors. Check the List of Learning Partners for a Cisco Learning Partner nearest you.

Additional Resources

A variety of Cisco Press Self Study titles may be available for this exam and may be purchased through the Cisco Bookstore in the Cisco Marketplace , directly through Cisco Press, or wherever you purchase technical books.

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