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IP Communications Quality of Service (QoS)
Exam Number: 642-642 Exam
Associated Certifications: IP Communications Quality of Service (QoS)
Duration: 182 Q&As
Available Language(s): English
Exam Details
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.

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642-642 Exam: Actualtests’s IP Communications Quality of Service (QoS) PDF
The IP Communications Quality of Service (QoS) PDF for preparing for the 642-642 exam – Actualtests ’s IP Communications Quality of Service (QoS). Actualtests is your premier source for practice tests, and true testing environment. Nothing will prepare you for your next exam like a Actualtests. You find it all here at ciscoexams.org.

QUESTION 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: A, B, E
Explanation:
Source: Cisco IP QoS Introduction, Page 64
QUESTION 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.
642-642
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Answer: A, D
Incorrect:
B. No hop-by-hop signaling uses per-hop behavior
C. This is a feature of both models
Sources: Cisco IP QoS Introduction
http://www.cisco.com/en/US/tech/ CK5 43/ CK7 66/technologies_white_paper09186a00800a3e2f.shtml
QUESTION 3:
The newly appointed Certkiller 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: B, D
Incorrect:
A. Shaping adds variable delay to traffic, possibly causing jitter
C. A shaper typically delays excess traffic using a buffer
E. This is a feature of policing
Explanation:
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Source: Cisco IP QoS Traffic Shaping and Policing
QUESTION 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
642-642
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D. 20 Mbps
E. 40 Mbps
Answer: D
Explanation:
In the configuration example, CAR is applied on the input and output of a customer
interface on the provider edge router. Traffic is policed to 256 Kbps on input and output,
with some bursting allowed. All exceeding traffic is dropped at the provider edge.
The result of the configuration is that traffic to and from the customer is limited to the
average rate of approximately 256kbps (256000 in the configuration) with sustained
bursts of approximately 32kbps (4kBps or 4000 in the configuration).
Initial bursts at line speed can last up to 3 seconds because the token bucket can hold up
to 96000 tokens (bytes) which equals 768000 bits (3 x 256000 bits).
Source: Cisco IP QoS Traffic Shaping and Policing, Page 4-91
QUESTION 5:
The newly appointed Certkiller 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
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Explanation:
Works on any (sub) interface type
Shapes traffic on that (sub)interface basis
Can use any physical interface queuing (FIFO, PQ, CQ or WFQ)
Only uses WFQ as the shaping queue (that is, on the input of the shaper)
In contrast, Frame Relay Traffic Shaping:
Works only on Frame Relay (sub) interfaces
Shapes traffic inside individual FR Virtual Circuits
Only permits WFQ as the physical interface queuing method
Can use any queuing method as the shaping queue (that is, on the input of the
shaper)
Source: Cisco IP QoS Traffic Shaping and Policing, Page 4-47
QUESTION 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
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Explanation:
Source: Cisco IP QoS Traffic Shaping and Policing, Page 4-58
QUESTION 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: A, C, E
Explanation:
A)DSCP is backward compatible with IP Precedence (Class Selector Code point, RFC
1812) but not with the ToS byte definition from RFC 791 (”DTR” bits)
Reference: Introduction to IP QoS (Course) p.45
QUESTION 8:
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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
Explanation:
IP precedence is encoded into the three high-order bits of the ToS field in the IP header.
It supports eight classes of which two are reserved and should not be used for
user-defined classes (IP precedence 6 and 7). IP precedence 0 is the default value and is
usually used for the best-effort class. The set ip precedence command marks packets of a
class with the specified precedence value.
Reference: Introduction to IP QoS (Course) p.9-104
QUESTION 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
Explanation:
To achieve the same level of quality in both directions the packets going to and coming
from the customer network must first be classified and marked.
Classification and marking packets going to the customer network is a more difficult task
because:
1) Classifying and marking must be performed on all edge routers.
2) Classifying and marking requires the identification of the customer network. Using
PBR, CAR, CB-Policing or CB-Marking does not scale because it involves the use of
access lists (this is especially difficult if customer networks are dynamically learned via
642-642
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BGP).
Reference: Introduction to IP QoS (Course) p.2-35
QUESTION 10:
The newly appointed Certkiller 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
Explanation:
The ATM CLP Setting feature somewhat allows users to extend their IP QoS policies
into an ATM network by setting the ATM CLP bit in ATM cells based on the IP
Precedence value of the packets being sent. As congestion occurs in the ATM network,
cells with the CLP bit set are more likely to be dropped, resulting in improved network
performance for high priority traffic and applications. The set
atm-clp
command marks packets of a class with the ATM CLP bit as a part of an input or output
policy.

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1.What is the purpose of the qos pre-classify command?
A. to enable the IOS to copy the ToS field from the original IP header to the outer tunnel IP header
B. to enable the IOS to copy the ToS field from the outer tunnel IP header back into the original IP header
C. to enable the IOS to classify the packet based on the original IP header instead of the tunnel IP
header
D. to enable the IOS to classify the packet based on the outer tunnel IP header instead of the original IP header
E. to enable class-based marking on tunnel interface
F. to enable class-based marking on IPSec crypto maps

Answer:C

2.What are two benefits of WFQ? (Choose two.)
A. WFQ is very easy to configure, and no manual traffic classification is necessary.
B. WFQ can provide fixed-bandwidth and fixed-delay guarantees. C. WFQ can provide fixed-bandwidth guarantees.
D. WFQ can provide fixed-delay guarantees.
E. WFQ prevents the large-volume flows with large packet size from starving out the low-volume flows with small packet size.
F. Based on DSCP, WFQ allows weighted, random dropping of packets when the WFQ system is full.

Answer:AE

3.Based on the configuration, which two of the following statements are true? (Choose two.)

A. This configuration will use a single token bucket.
B. This configuration will drop all exceeding traffic. C. This is a dual-rate, class-based policing example. D. This is a percentage-based policing example.
E. This is a multi-action, class-based policing example. Answer:CD

4.Based on the configuration, which two statements are true? (Choose two.)

A. The interactive traffic class will have a minimum bandwidth guarantee of 256 kbps.
B. The interactive traffic class will have a maximum bandwidth guarantee of 256 kbps.
C. If the interactive traffic class exceeds an average rate of 256 kbps, the traffic rate will be throttled down to 128 kbps.
D. This configuration allows class-based traffic shaping to lower the traffic rate in response to the
BECN bit.
E. The interactive traffic class will have a min-rate (min-cir) of 128 kbps. Answer:DE
5.Which technology is required when configuring FRF.12 on a Cisco device? A. FRF11.c
B. FRF.8
C. VoFR
D. MLP with interleaving
E. FRTS F. WRED

Answer:E

6.What are three methods of reducing delay for critical applications in a converged network?
(Choose three.)
A. Apply payload compression. B. Increase link capacities.
C. Apply header compression. D. Increase LFI fragment size. E. Reduce inter-packet gaps.
F. Increase all queue depths. Answer:ABC

7.At the network layer, IP packets are typically classified based on which three items? (Choose three.)
A. packet length
B. VLAN Identifier
C. flow control bits
D. source and destination IP addresses
E. content of the ToS byte

Answer:ADE

8.What are three reasons link efficiency mechanisms are deployed on WAN links? (Choose three.)
A. decrease delay
B. decrease jitter
C. increase link speed
D. increase throughput
E. decrease propagation delay

Answer:ABD

9.Which mechanism is used for the prioritizing, protection, and isolation of traffic based on marking?
A. classification and marking
B. congestion management
C. congestion avoidance
D. metering E. policing F. shaping

Answer:B

10. Click and drag each statement on the left to the proper traffic policing method on the right.

Bc is the maximum number of
tokens accumulated.

Single Rate–Single Bucket

Bc + Be is the maximum number of
tokens accumulated.

Traffic is policed using two separate
rates.

Tokens exceeding Bc are discarded.

Single Rate–Dual Bucket

Traffic exceeding the normal burst
rate is marked.

Tp bucket is checked to determine if
the traffic rate is in violation.

Dual Rate

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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
Exam Policies: Read current policies and requirements
Exam Tutorial: Review type of exam questions
QUESTION 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: A, B, E Explanation:

Source: Cisco IP QoS Introduction, Page 64

QUESTION 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: A, D Incorrect:
B. No hop-by-hop signaling uses per-hop behavior

TK

642-642

C. This is a feature of both models
Sources: Cisco IP QoS Introduction
http://www.cisco.com/en/US/tech/ CK5 43/ CK7 66/technologies_white_paper09186a00800a3e2f.shtml

QUESTION 3
The newly appointed Certkiller 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: B, D Incorrect:

A. Shaping adds variable delay to traffic, possibly causing jitter
C. A shaper typically delays excess traffic using a buffer
E. This is a feature of policing

Explanation:

Source: Cisco IP QoS Traffic Shaping and Policing

QUESTION 4
Study the Exhibit below carefully:
Router# show interfaces hssi 0/0/0 rate-limit
Hssi0/0/0 45Mbps to R1

TK

642-642

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 Explanation:

In the configuration example, CAR is applied on the input and output of a customer interface on the provider edge router. Traffic is policed to 256 Kbps on input and output, with some bursting allowed. All exceeding traffic is dropped at the provider edge.
The result of the configuration is that traffic to and from the customer is limited to the
Exam 642-642: Quality of Service Exam (QOS)

Related Certifications: CCIP, CCVP, IP Telephony Specialists Certifications.

Number of Questions: 45-55 Duration: 90 minutes

Exam Topics Include:

IP QoS Fundamentals and Best Practices
IP QoS Components
Modular QoS CLI and Auto-QoS
Classification and Marking
Congestion Management and Avoidance Methods
Traffic Policing and Shaping
Link Efficiency Mechanisms
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 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 importance of this exam is evident in the fact that it applies to so many different certifications.

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Updated : 08/14/2008
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Exam Number/Code: 642-642
Exam Name: IP Communications Quality of Service (QoS)
VUE Code: 642-642
Questions Type: Single choice,
Question Numbers of Real-exam: 45-55 questions

Exam : Cisco 642­642

Title :

Cisco. Quality of Service (QoS)

Update : Demo

1.What is the purpose of the qos pre­classify command?
A. to enable the IOS to copy the ToS field from the original IP header to the outer tunnel IP header
B. to enable the IOS to copy the ToS field from the outer tunnel IP header back into the original IP header
C. to enable the IOS to classify the packet based on the original IP header instead of the tunnel IP header
D. to enable the IOS to classify the packet based on the outer tunnel IP header instead of the original IP
header
E. to enable class­based marking on tunnel interface
F. to enable class­based marking on IPSec crypto maps
Answer: C

2.What are two benefits of WFQ? (Choose two.)
A. WFQ is very easy to configure, and no manual traffic classification is necessary. B. WFQ can provide fixed­bandwidth and fixed­delay guarantees.
C. WFQ can provide fixed­bandwidth guarantees. D. WFQ can provide fixed­delay guarantees.
E. WFQ prevents the large­volume flows with large packet size from starving out the low­volume flows with small packet size.
F. Based on DSCP, WFQ allows weighted, random dropping of packets when the WFQ system is full. Answer: AE

3.Based on the configuration, which two of the following statements are true? (Choose two.)

A. This configuration will use a single token bucket.
B. This configuration will drop all exceeding traffic.
C. This is a dual­rate, class­based policing example. D. This is a percentage­based policing example.
E. This is a multi­action, class­based policing example. Answer: CD

4.Based on the configuration, which two statements are true? (Choose two.)

A. The interactive traffic class will have a minimum bandwidth guarantee of 256 kbps.
B. The interactive traffic class will have a maximum bandwidth guarantee of 256 kbps.

C. If the interactive traffic class exceeds an average rate of 256 kbps, the traffic rate will be throttled down
to 128 kbps.
D. This configuration allows class­based traffic shaping to lower the traffic rate in response to the BECN
bit.
E. The interactive traffic class will have a min­rate (min­cir) of 128 kbps. Answer: DE

5.Which technology is required when configuring FRF.12 on a Cisco device? A. FRF11.c
B. FRF.8
C. VoFR
D. MLP with interleaving
E. FRTS F. WRED Answer: E

6.What are three methods of reducing delay for critical applications in a converged network? (Choose three.)
A. Apply payload compression. B. Increase link capacities.
C. Apply header compression. D. Increase LFI fragment size. E. Reduce inter­packet gaps.
F. Increase all queue depths. Answer: ABC

7.At the network layer, IP packets are typically classified based on which three items? (Choose three.)
A. packet length
B. VLAN Identifier
C. flow control bits
D. source and destination IP addresses
E. content of the ToS byte
Answer: ADE

8.What are three reasons link efficiency mechanisms are deployed on WAN links? (Choose three.)
A. decrease delay
B. decrease jitter
C. increase link speed
D. increase throughput
E. decrease propagation delay
Answer: ABD

9.Which mechanism is used for the prioritizing, protection, and isolation of traffic based on marking?
A. classification and marking

B. congestion management
C. congestion avoidance
D. metering E. policing F. shaping Answer: B

10.For which service is assured forwarding PHB used? A. best effort
B. expedited forwarding C. guaranteed bandwidth D. class selector
Answer: C

11.Which three factors will affect processing delay? (Choose three.) A. CPU speed
B. router architecture
C. queuing mechanism
D. type of media
E. IP switching method F. distance of media Answer: ABE

12.which four of the following bit values are used for bits 5­7 of the DSCP field to select AF PHB? (Choose four.)
A. 000
B. 001
C. 010
D. 011
E. 100
F. 101
Answer: BCDE

13.Based on the following 2950 switch configurations, which statement is correct?

A. Queue 1 is setup as the expedite queue.
B. Queue 2 is setup as the expedite queue. C. Queue 3 is setup as the expedite queue. D. Queue 4 is setup as the expedite queue. E. No queue is setup as the expedite queue.
Answer: E

14.When LLQ is being configured, which IOS command is used to limit the traffic rate on the priority queue even when the other class queues are not congested?
A. priority
B. bandwidth C. queue­limit D. police
E. hold­queue
Answer: D

15.Where is the error in the following policy­map configuration?

A. The bandwidth command is not a valid command for the class­default traffic class in this case.
B. The voice traffic class is missing the random­detect command.
C. The mission­critical traffic class bandwidth guarantee should be lower than the voice traffic class priority bandwidth guarantee.
D. The mission­critical traffic class is missing the queue­limit command. E. Fair­queue should be enabled for the mission­critical traffic class. Answer: A

16.QoS policy propagation through BGP (QPPB) supports which two QoS markers? (Choose two.)

A. DSCP
B. IP precedence
C. QoS group
D. COS
E. MPLS EXP Answer: BC

17.Which element is mandatory for QoS policy propagation through BGP operations? A. MPLS
B. NBAR C. CEF
D. QoS pre­classify
E. policy­based routing
F. MQC Answer: C
18.Based on the following policy­map configuration, the bulk traffic class packets are not being ECN
marked, yet there are many random drops in the bulk traffic class. What is the most likely cause of the

problem?

A. The CB­WRED min threshold is set too low.
B. The CB­WRED max threshold is set too high.
C. The CB­WRED mark probability denominator is set too low.
D. The endpoints generating the bulk traffic packets are not ECN capable. E. Some of the routers within the traffic path are not ECN capable.
Answer: D

19.Which two of the following statements about CBWFQ are correct? (Choose two.)
A. The CBWFQ scheduler provides a guaranteed amount of minimum bandwidth to each class.
B. CBWFQ services each class queue using a strict priority scheduler. C. The class­default queue only supports WFQ.

D. Each CBWFQ traffic class is policed using a congestion aware policer.
E. Inside a class queue, processing is always FIFO, except for the class­default queue. Answer: AE

20.Which of the following configurations requires the use of hierarchical policy maps? A. the use of class­based WRED within a CBWFQ class queue
B. the use of a strict priority­class queue within CBWFQ C. the use of CBWFQ inside class­based shaping
D. the use of nested class­maps with class­based marking
E. the use of both the bandwidth and shape statements within a CBWFQ class queue Answer: C

21.The following commands have been configured under the fa0/1 interface on the 2950 switch: Voice
traffic from the IP phone that is directly connected to the fa0/1 interface is experiencing excessive delays.

What could be the cause of this problem?

A. The wrr­queue bandwidth weightings are not correct. B. The default wrr­queue cos­map is being used.
C. The default cos­to­dscp map is being used. D. The default dscp­to­cos map is being used.
E. The trust boundary configuration is not correct. Answer: B

22.Which QoS mechanism adds IP Precedence information for prefixes into the FIB table?
A. QoS pre­classify
B. AutoQoS C. QPPB
D. Class­Based Marking
E. LLQ
F. Class­Based WRED Answer: C

23.Refer to the partial router configuration. Which two of the following statements are true? (Choose two.)

A. The configuration is invalid since it refers to a class map within a different class.
B. The class­map class1 command will set the qos­group value to 4 for all IP packets.
C. Regardless of destination IP address, all traffic sent to Mac address 1.2.3 will be subject to policing
D. Only those packets which satisfy all of the matches in class1 and class2 will be subject to policing.
E. All traffic from a server with the IP address of 147.23.54.21 will be subject to policing.
F. Any IP packet will be subject to policing. Answer: CE

24.In a typical converged campus network, which two of the following are considered QoS best practices?
(Choose two.)
A. Traffic classification and marking is performed as close to the traffic source as possible.
B. Traffic classification and marking is performed at the high speed core layer. C. Ensure voice traffic is serviced by a weighted fair queue.
D. Only a reasonable number of applications should be classified into the mission­critical traffic class.
E. NBAR is used at the high speed core layer to discover and classify network applications.
F. Catalyst switches should use weighted round robin (WRR) queuing giving the voice traffic the highest priority.
Answer: AD

25.Which three characteristics are drawbacks to the use of a best­effort with over­provisioning backbone design? (Choose three.)
A. The design costs more to implement than a DiffServ backbone.
B. Denial of Service attacks on one service can affect all network traffic.
C. The design uses a different over­provisioning ratio for the different traffic classes. D. It requires complex QoS mechanisms at the network edge.
E. It requires complex QoS mechanisms at the network core.
F. Unplanned network failures can cause unexpected congestion in the network. Answer: ABF

26.Which two different traffic types have the most similar sensitivity to latency, jitter, and packet loss?
(Choose two.)
A. SQL transactions
B. voice
C. voice signaling
D. streaming video
E. video conferencing
F. peer­to­peer file sharing
Answer: BE

27.To determine the bandwidth requirement for each VoIP call, not including Layer 2 overhead, how much bandwidth per call should be added to account for the voice signaling traffic?
A. 20 bps B. 40 bps C. 150 bps D. 240 bps E. 480 bps F. 640 bps Answer: C

28.What does the following command accomplish?

A. enables the router to lower the shaping rate when BECN bits are received
B. enables the router to lower the shaping rate when FECN bits are received
C. enables the router to respond to FECN bits by creating test frames in the opposite direction with the
BECN bit set
D. enables the router to respond to BECN bits by creating test frames in the opposite direction with the
FECN bit set
E. enables the router to increase the shaping rate when BECN bits are received
F. enables the router to increase the shaping rate when FECN bits are received
Answer: C

29.What will be the peak shape rate based on the configuration that follows?

A. 16000 bps
B. 32000 bps

C. 48000 bps
D. 64000 bps E. 80000 bps F. 96000 bps Answer: D

30.Which QoS mechanism calculates the mean queue depth to determine its operation?
A. WRED
B. LLQ/CBWFQ C. WFQ
D. class­based shaping E. class­based policing Answer: A

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“IP Communications Quality of Service (QoS)”, also known as 642-642 exam, is a Cisco certification.
Preparing for the 642-642 exam? Searching 642-642 Test Questions, 642-642 Practice Exam, 642-642 Dumps?

With the complete collection of questions and answers, Pass4sure has assembled to take you through 90 Q&As to your 642-642 Exam preparation. In the 642-642 exam resources, you will cover every field and category in IP Communications helping to ready you for your successful Cisco Certification.
Questions and Answers : 90 Q&As
Updated: April 24th , 2008
Market Price: $125.99
Member Price: $99.99
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.
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Exam Name: IP Communications Quality of Service (QoS)

“IP Communications Quality of Service (QoS)”, also known as 642-642 exam, is a Cisco certification.
Preparing for the 642-642 exam? Searching 642-642 Test Questions, 642-642 Practice Exam, 642-642 Dumps?

With the complete collection of questions and answers, Pass4sure has assembled to take you through 90 Q&As to your 642-642 Exam preparation. In the 642-642 exam resources, you will cover every field and category in IP Communications helping to ready you for your successful Cisco Certification.

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Practice Exam 642-642
 Product Description:
Exam Number/Code: 642-642
Exam Name: CCIP CCVP IP Communications

  Quality of Service (QoS) 
 
 Test Q&A Updated Price
 642-642 76: Q&A 2008-4-18 USD:  79.00

 
 
 
 
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    Course Content           Course Outline
Prerequisites           Who Should Attend
 

   
  Completion of Interconnecting Cisco Networking Devices (ICND) or Cisco Certified Networking Associate (CCNA). The Configuring BGP on Cisco Routers course (BGP) or equivalent is recommended because some BGP background is assumed for the QoS course. 

   
  The Implementing Cisco Quality of Service (QoS) v2.2 course provides students with in-depth knowledge of IP QoS requirements, conceptual models using Differentiated Services (DiffServ), Integrated Services (IntServ) and Best Effort (over provisioning), and the implementation of IP QoS on Cisco IOS switch and router platforms.
Course Objectives

After completing this course the student should be able to:

Identify the components of the Cisco Unity system, describe their standard and optional features, and explain and how they integrate into a unified messaging system
explain the need to implement Quality of Service (QoS) and explain methods for implementing and managing QoS
identify and describe different models used for ensuring QoS in a network and explain key IP QoS mechanisms used to implement the models
explain the use of MQC and AutoQoS to implement QoS on the network
use Cisco QoS queuing mechanisms to manage network congestion
use Cisco QoS congestion avoidance mechanisms to reduce the effects of congestion on the network
use Cisco QoS traffic policing and traffic shaping mechanisms to effectively limit the rate of network traffic
successfully use Cisco link efficiency mechanisms to improve the bandwidth efficiency of the link
correctly select the most appropriate QoS mechanisms for providing QoS using Cisco best practices
 

   
  Introduction to IP QoS

The Building Blocks of IP QoS

Introduction to Modular QoS CLI and Auto-QoS

Classification and MarkingModule

Congestion Management

Congestion Avoidance

Traffic Policing and Shaping

Link Efficiency Mechanisms

QoS Best Practices
 

    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
Exam Policies: Read current policies and requirements
Exam Tutorial: Review type of exam questions
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
 
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642-642 Practice engine

642-642 question and answers

    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
Exam Policies: Read current policies and requirements
Exam Tutorial: Review type of exam questions
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 

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