Exam Number/Code: 642-642
Exam Name: Quality of Service (QoS)
For candidates making preparation for the Cisco 642-642 exam, what they most desire is to easily pass the 642-642 (Quality of Service (QoS)) exam. PassGuide 642-642 includes 180 questions and answers, which are collected and collated by experts of Cisco. With our 642-642 study materials, you can successfully take Cisco certification of 642-642 exam and go further on Cisco career path.
Quality of Service (QOS)
Q&A V3.20
www.PassGuide.com
(C) Copyright 2006-2009 CertBible Tech LTD,All Rights Reserved.
Important Note
Please Read Carefully
Study Tips
This product will provide you questions and answers carefully compiled and written by our experts. Try to understand the concepts behind the questions instead of cramming the questions.
Go through the entire document at least twice so that you make sure that you are not
missing anything.
Latest Version
We are constantly reviewing our products. New material is added and old material is
revised. Free updates are available for 120 days after the purchase. You should check your
member zone at PassGuide an update 3-4 days before the scheduled exam date.
Feedback
If you spot a possible improvement then please let us know. We always interested in
improving product quality.
Feedback should be send to feedback@passguide.com. You should include the following:
Exam number, version, page number, question number, and your login ID.
Our experts will answer your mail promptly.
Be Prepared. Be Confident. Get Certified.
————————————————————————————————————————-
Sales and Support Manager
Sales Team: sales@passguide.com Support Team: support@passguide.com
———————————————————————————————————————
Copyright
Each pdf file contains a unique serial number associated with your particular name and
contact information for security purposes. So if we find out that a particular pdf file is
being distributed by you, CertBible reserves the right to take legal action against you
according to the International Copyright Laws.
1. Which of the following markers can be set by Committed Access Rate (CAR)? (Choose all that apply.)
A. DSCP bits
B. QoS Group
C. ATM CLP bit
D. Frame Relay DE bit
E. IP precedence bits
Answer: ABE
2. What makes the DiffServ model more scalable than the IntServ model? (Choose all that apply.)
A. DiffServ makes use of per-aggregate QoS instead of per-flow QoS.
B. DiffServ makes use of hop-by-hop signaling which allows DiffServ to scale to a larger number of application flows.
C. DiffServ is capable of implementing admission control either locally on the routers or be offloaded to a central policy server using the COPS protocol.
D. DiffServ routers are not compelled to track the state information for each individual flow.
Answer: AD
3. The newly appointed PassGuide trainee technician wants to know what the benefits of using traffic shaping to implement network rate limiting is.What will your reply be? (Choose all that apply.)
A. Traffic shaping is an effective tool for rate-limiting VoIP traffic.
B. It will not increase packet loss.
C. It will not add to packet transit delays.
D. Traffic shaping can interact with congestion mechanisms embedded in Frame Relay.
E. Traffic shaping can be used on inbound and outbound traffic on a router.
Answer: BD
4. Study the Exhibit below carefully: Router# show interfaces hssi 0/0/0 rate-limit Hssi0/0/0 45Mbps to R1 Input matches: all traffic params: 20000000 bps, 24000 limit, 24000 extended limit conformed 8 packets, 428 bytes; action: transmit exceed 0 packets, 0 bytes; action: drop last packet: 8680ms ago, current burst: 0 bytes last cleared 00:03:59 ago, conformed 0 bps, exceed 0 bps Output matches: all traffic params: 20000000 bps, 24000 limit, 24000 extended limit conformed 0 packets, 0 bytes; action: transmit exceed 0 packets, 0 bytes; action; drop last packet: 8680ms ago, current burst: 0 bytes last cleared 00:03:59 ago, conformed 0 bps, exceed 0 bps According to the exhibit, the router has been configured with Committed Access Rate (CAR) to rate limit traffic. What data rate has the traffic been limited to?
A. 192 Kbps
B. 2400 Kbps
C. 4,5 Mbps
D. 20 Mbps
E. 40 Mbps
Answer: D
5. The newly appointed PassGuide trainee technician wants to know which type of software queuing mechanism is Frame Relay Traffic Shaping implemented with on the physical interface. What will your reply be?
A. Priority Queuing (PQ)
B. Custom Queuing (CQ)
C. FIFO
D. Weighted Fair Queuing (WFQ)
E. IP Real Time Transport Protocol (RTP) Priority
Answer: D
6. Why is it beneficial to make use of Enhanced LMI (ELMI) on Cisco networks?
A. ELMI is responsible for providing virtual provisioning tools at the edge of the Frame Relay network.
B. ELMI permits routers to dynamically download QoS information from Cisco switches for use in traffic shaping or for congestion management purposes.
C. ELMI provides the router the ability to use additional QoS tools including rate limiting with CAR and the Modular QoS Command Line Interface (MQC).
D. ELMI allows the router to deliver packets at the line rate of the Frame Relay interface, regardless of the condition of the Frame Relay network.
Answer: B
7. Which of the following statements are true when you compare DSCP and IP Precedence to each other? (Choose all that apply.)
A. DSCP is backwards compatible with IP Precedence.
B. DSCP cannot be easily mapped into QoS because of its expanded classification options.
C. DSCP is more granular the IP Precedence, since more marking combinations are available.
D. DSCP appears stubby when compared IP Precedence, since devices make use of DSCP as defined in RFC exclusively.
E. DSCP is 6 bits long and IP Precedence is 3 bits long.
F. DSCP is more restrictive than IP Precedence, since devices are only allowed to use DSCP as defined in RFCs.
Answer: ACE
8. Which MQC command would you use to perform marking properly?
A. precedence 5
B. ip precedence 5
C. set ip precedence 5
D. set ip mark precedence 5
E. mark ip precedence 5
Answer: C
9. Which of the following statements aptly describes a network well designed for QoS?
A. Packets are classified at each router, based on as many detail as possible, typically using extended IP ACLs to match the packets for classification.
B. Packets are classified at each router, based on socket address only, typically using extended IP ACLs to match the packets for classification.
C. Packets are classified and marked, close to the edge of the network. The packets are treated differently based on this marking at the routers in the middle of the network.
D. Packets are classified based on different parameters, but close to the edge of the network. The packets are automatically characterized based on flow at the routers.
E. Packets are classified based on socket address, at the router closest to the source of the traffic. The packets are automatically characterized based on flow at the routers.
Answer: C
10. The newly appointed PassGuide trainee technician wants to know which bit in the ATM header can be marked by the Class Based Marker to extend IP QoS policy into an ATM network. What will your reply be?
A. DE
B. PTI
C. FECN
D. CLP
E. BECN
Answer: D
11. How many possible meaningful values are defined in the DSCP in a Differentiated Services environment?
A. 3
B. 8
C. 16
D. 32
E. 64
F. 128
Answer: E
12. Which of the following features will allow the marking of packets according to the Cisco QoS Framework? (Choose all that apply.)
A. MQC
B. CQ
C. PQ
D. CAR
E. WRED
Answer: AD
13. Which of the following can be classified as Call Admission Control methods? (Choose all that apply.)
A. GTS
B. Advanced Busyout Monitor
C. RSVP
D. NBAR
E. Max Connections
F. AVBO.
Answer: CEF
14. What are the benefits, as listed in the DQOS course, for Enterprise Networks when QoS is implemented? (Choose all that apply.)
A. It decreases propagation delay.
B. It provides predictable response times.
C. It prevents the need to increase bandwidth.
D. It supports dedicated bandwidth per application.
E. It maximizes loss during bursty congestion.
Answer: BD
15. Which of the following is most likely to occur for voice in the absence of QoS? (Choose all that apply.)
A. choppy speech
B. words out of order due to recovery
C. disconnect calls
D. unsynchronized voice patterns
E. softer volume speech
Answer: AC
16. Auto QoS is which type of Cisco IOS command?
A. interface
B. global
C. policy-map
D. service-map
E. serial interface only
Answer: A
17. Which two components are associated with the DiffServ model? (Choose two.)
A. hop-by-hop signaling
B. per-hop behavior
C. RSVP
D. Hard QoS
E. DSCP use of class selector
Answer: BE
18. What is true about a DSCP marked packet when it reaches an IP precedence based device?
A. The eight DSCP bits are all set to zero.
B. The last three bits of the DSCP are set to 101.
C. The 8 DSCP AF classes will be mapped into the 8 levels of IP precedence.
D. Bits 7-5 of DSCP have the same position and meaning as IP precedence.
Answer: D
19. SIMULATION Simulation Exhibit:
You are working as a network administrator at PassGuide.com. You are required to configure the PassGuide 1 WAN edge router: you must configure the appropriate MQC based queuing mechanism for the outbound traffic to the WAN (S0/0) so that the following bandwidth requirements will be met. A strict priority queue with a 168 Kbps bandwidth guarantee for the class voice is reserved, a minimum bandwidth guarantee of 30 Kbps is configured for the class interactive, a minimum bandwidth guarantee of 16 Kbps for class bulk, and the default class is configured for WFQ with no bandwidth guarantee. In addition, also limit the bulk traffic class to an average rate of 24 Kbps by buffering excess traffic (use the IOS default Bc and Be). In addition, also limit the bulk traffic class to an average rate of 24 Kbps by buffering excess traffic (use the IOS default Bc and Be).
Use a policy-map called “IIq-policy” and reference the existing class-maps already configured on the PassGuide 1 router. Traffic Class Name Bandwidth Guarantee voice 168 Kbps maximum (use the IOS default burst value) interactive 30 Kbps minimum bulk 16 Kbps minimum (For the bulk traffic class, also limit the traffic to an average rate of 24 Kbps by buffering excess traffic (use the IOS default Bc and Be)) class-default Weighted Fair Queue with no bandwidth guarantee
Simulation Output exhibit #2.
Answer:
PassGuide 1(config)#policy-map llq-policy
PassGuide 1(config-pmap)#class voice
PassGuide 1(config-pmap-c)#priority 168
PassGuide 1(config-pmap-c)#class interactive
PassGuide 1(config-pmap-c)#bandwidth 30
PassGuide 1(config-pmap-c)#class bulk
PassGuide 1(config-pmap-c)#bandwidth 16
PassGuide 1(config-pmap-c)#shape average 2400
PassGuide 1(config-pmap-c)#class class-default
PassGuide 1(config-pmap-c)#fair-queue
PassGuide 1(config-pmap-c)#interface serial 0/0
PassGuide 1(config-if)#service-policy output llq-policy
PassGuide 1(config-if)#end
PassGuide 1#copy running-config startup-config
20. Command exhibit: mis qos trust pass-through dscp Your apprentice PassGuide is configuring a Catalyst 2950 Switch. What is the purpose of the command she is submitting (see exhibit)?
A. The command configures a port to trust the incoming CoS and not modify the incoming DSCP when sending the frame out.
B. The command configures a port to trust the incoming CoS and to generate the internal DSCP based on the incoming CoS. The internalr DSCP will then determine the gress DSCP.
C. The command configures a port to trust the incoming CoS and DSCP values.
D. The command configures a port to trust the incoming CoS and to generate the internal DSCP based on the incoming DSCP. The internal DSCP will then determine the egress DSCP.
E. The command configures a port to trust the incoming CoS and bypass the CoS-to-DSCP maps for generating the internal DSCP.
F. The command configures a port to trust the incoming CoS and bypass the DSCP-to-CoS maps for generating the egress CoS.
Answer: A
21. Which of the following tasks are necessary when configuring Service Assurance Agent (SAA agent)? (Choose all that apply.)
A. You must schedule the operation
B. You must configure the data collection frequency
C. You must configure the operation type
D. You must configure a collection probe on the router
E. You must configure timer parameters for the SAA agent
Answer: AC
22. The SSA agent is used to measure which of the following SLA metrics? (Choose all that apply.)
A. jitter
B. interface utilization
C. packet loss
D. response time
E. client response
F. router buffer allocation
Answer: ACD
23. Which of the following is part of SMS? (Choose all that apply.)
A. QDM
B. CiscoWorks2000 Resource Manager Essentials
C. RSVP COPS Server
D. Service Level Manager
E. CiscoViewCiscoWorks 2000 Management Server
F. All of the above
Answer: BDE
24. You are using IP to ATM CoS. Which action can be configured to be automatically taken should a VC in a VC bundle fail?
A. The VC can be remapped to a different bundle.
B. The VC can be declared down and an alternate route requested.
C. The circuit data can be transferred or “bumped” to a lower priority VC.
D. The circuit data can be divided equally between the remaining VCs in the bundle.
Answer: C
25. How is IP to ATM CoS supported in a single VC?
A. The IP Precedence bits are mapped into the unused upper bits of the VPI field.
They are treated accordingly as they are switched through the ATM network.
B. The router at the edge of the ATM network sets the ATM CLP based on the IP Precedence bits.
Lower priority packets are transported in lower priority cells.
They are treated accordingly as they are switched through the ATM network.
C. WRED/DWRED is used in the routers at the edge of the ATM network.
Based on the IP Precedence bits, IP traffic is subjected to different drop probabilities (and therefore priorities) as IP traffic coming into a router competes for bandwidth on the ATM VC.
D. PQ-WFQ is used in the routers at the edge of the ATM network.
Based on the IP Precedence bits, IP traffic is then properly queued and de-queued as IP traffic competes for bandwidth on the ATM VC.
Answer: C
26. You are the network administrator at PassGuide . The newly appointed PassGuide trainee wants to know which LFI mechanism has an option for fragmentation by the Frame Relay DTE, with the switch reassembling the fragments. What will your reply be?
A. FRF .3
B. FRF .9
C. FRF .11 Annex C
D. FRF.12
E. FRF.6
Answer: D
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: BD
