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QUESTION 91
Which of the following statements regarding cRTP compression is valid?
A. IP, TCP, and RTP headers are compressed, since the headers are uncompressed on the other end of the link.
B. UDP and RTP headers are compressed, but the IP header is not, so the VoIP packets can be delivered to the terminating gateway.
C. IP, UDP, and RTP headers are compressed, since the headers are uncompressed on the other end of the link.
D. TCP and RTP headers are actually removed, with a smaller header added that includes information that has changed since the last full header sent.
E. None of the above.

Correct Answer: C Section: (none) Explanation
Explanation/Reference:
Explanation:
When using RTP compression IP packets that also have RTP headers are compressed. The compression
algorithm does not compress the data-link header or trailer. It does compress the IP, UDP, and RTP
headers. It does not compress any user data that follows the RTP header.

QUESTION 92
You are the network administrator at Certkiller . The newly appointed Certkiller trainee wants to know what the approximate bandwidths required for a G.729a VoIP call with and without cRTP enabled is. What will your reply be?
A. 5.3 Kbps/8 Kbps
B. 11 Kbps/26 Kbps
C. 12 Kbps/24 Kbps
D. 28 Kbps/64 Kbps
E. none of the above.

Correct Answer: C Section: (none) Explanation
Explanation/Reference: QUESTION 93

Which packet will most likely be dropped by Weighted Fair Queuing (WFQ) during periods of traffic congestion?
A. The newest packet.
B. The packet with the worst finish time.
C. The largest packet.
D. The packet with the lowest priority.

Correct Answer: B Section: (none) Explanation
Explanation/Reference:
Explanation: The figure illustrates the dropping scheme of WFQ. The process can be split into the following steps: Step 1 Drop the new packet if the WFQ system is full (hold-queue limit reached) and the new packet has the worst finish time (the last in the entire system). Step 2 Drop the packet with the worst finish time in the WFQ system if the system is full. Enqueue the new packet Step 3 Drop the new packet if the queue, where the packet should be enqueued, is the longest (not in packets but in the finish time of the new packet) and there are more packets in the WFQ system than the CDT. Step 4 Otherwise enqueue the new packet. Source: Cisco Queuing Mechanisms, Page 3-61

QUESTION 94
The newly appointed Certkiller trainee technician wants to know what is the reason why Weighted Fair Queuing (WFQ) is disabled on WAN interfaces using X.25, SDLC, LAPB, or reliable PPP encapsulations. What will your reply be?
A. These protocols require strict priority scheduling which is not WFQ is not capable of supporting.
B. These encapsulations require sequenced packets which is contradictory to the way in which WFQ works.
C. Each of these protocols has a pre-defined compulsory queuing scheme.
D. These protocols require delay characteristics which WFQ-enabled routers are incapable of.

Correct Answer: B Section: (none) Explanation
Explanation/Reference:
Explanation: The figure explains the default behavior of WFQ. As mentioned previously, WFQ is automatically enabled on all interfaces slower than 2Mbps. WFQ is also required on interfaces using Multilink PPP. WFQ cannot be used if reordering of frames is not allowed due to sequence numbering of Layer-2 frames or if the switching path does not support WFQ. Source: Cisco Queuing Mechanisms, Page 3-79

QUESTION 95
Which of the following statements aptly describes what the result of enabling Weighted Fair Queuing (WFQ) on a low-speed router interface is?
A. Bandwidth is guaranteed for different traffic queues.
B. Delay is guaranteed for high-priority traffic types.
C. Fixed-size queues are pre-allocated for different traffic flows.
D. Low-bandwidth traffic receives priority over high-bandwidth traffic.

Correct Answer: D Section: (none) Explanation
Explanation/Reference:
Explanation:
WFQ solves the problem of low-bandwidth traffic starvation. This is fair protocol and gives same bandwidth
to all queues. For example if in queue 1 the packets are 100 kb each and in queues 2300kb each than 3
packets from queue 1 will go through the interface than 1 packet from queue 2 and so on.

QUESTION 96
Under which circumstances will Cisco IOS bypass the transmit software queue on an interface and place the packet directly into the hardware queue?
A. When LLQ has been enabled.
B. When the software queue is full.
C. When the software queue is empty.
D. When the software queue has reached its MCC.

Correct Answer: C Section: (none) Explanation
Explanation/Reference:
Explanation:

The implementation of software queuing was optimized for periods when the interface is not congested. The software queuing system is bypassed whenever there is no packet in the software queue and there is room in the hardware queue. The software queue is, therefore, only used when data must wait to be placed into the hardware queue. Source: Cisco Queuing Mechanisms, Page 3-6
QUESTION 97
Which of the following statements regarding the queuing scheme of IP Real Time Transport Protocol (RTP) prioritization is valid?
A. It is capable ofsupporting TCP traffic.
B. It is used mainly for interactive traffic.
C. It is responsible for providing low latency queuing by providing a high priority queue.
D. Packets that exceed the queue’s configured rate are placed into the default queue.

Correct Answer: C Section: (none) Explanation
Explanation/Reference:
Explanation:

IP RTP Prioritization is an add-on to WFQ to support low-delay propagation of packets.
It can be used for UDP traffic only.
IP RTP Prioritization also polices the high priority traffic to prevent starvation of other queues.
IP RTP Prioritization supports one high priority queue. Packets from this queue are scheduled ahead of other packets as long as they are within the configured rate.
Excess packets are dropped.
Sources: Cisco Queuing Mechanisms, Pages 3-134, 3-135

QUESTION 98
Which of the following are versions of distributed WFQ (dWFQ)? (Choose all that apply.)
A. CAR-based dWFQ
B. QPPB-based dWFQ
C. flow-based dWFQ
D. ToS-based dWFQ
E. DiffServ-based dWFQ
F. precedence-based dWFQ

Correct Answer: CD Section: (none) Explanation
Explanation/Reference:
Explanation:

The distributed versions of Weighted Fair Queuing are implemented on Cisco 7×00 series routers with Versatile Interface Processors (VIPs). There are four different versions of distributed WFQ, three of which are discussed in this module: Flow-based dWFQ or simply dWFQ ToS-based dWFQ QoS-group-based dWFQ or QoS-based dWFQ VIP is basically a router within a router. It has its own processor and its own (different) version of the IOS. Most features implemented on VIPs have different functionality than those available on the Route Switch Processor (RSP). Source: Cisco Queuing Mechanisms, Page 3-86
QUESTION 99
The newly appointed Certkiller trainee technician wants to know what the difference is between Low
Latency Queuing (LLQ) and IP Real-Time Transport Protocol (RTP) priority. What will your reply be?
A. LLQ is not limited to defining traffic flows when making use of UDP port numbers.
B. IP RTP Priority has the ability to specify traffic matches based on DSCP whereas LLQ cannot.
C. LLQ can accommodate voice traffic that is not supported in IP RTP Priority configurations.
D. LLQ priority queues suffer from “starvation” of low priority traffic due to preferential treatment of the high priority queue.

Correct Answer: A Section: (none) Explanation
Explanation/Reference:
Explanation:

IP RTP Prioritization is an add-on to WFQ to support low-delay propagation of packets. It can be used for
UDP traffic only.
IP RTP Prioritization also polices the high priority traffic to prevent starvation of other queues.
Source: Cisco Queuing Mechanisms, Page 3-134

QUESTION 100
Which of the following represent important advantages of applying QoS to IP networks? (Choose all that apply.)
A. QoS manages packet loss during periods of bursty congestion.
B. QoS facilitates the integration of differing traffic types such as voice, video, and data into a single infrastructure.
C. QoS is capable of preoviding performance enhancements for commercial application issues such as server sizing and tuning.
D. QoS allows the control usage patterns of network applications.
E. QoS is capable of solving traffic problems on low bandwidth, high-latency, high-loss WAN links.

Correct Answer: ABE Section: (none) Explanation
Explanation/Reference:
QUESTION 101
What are three features of CBWFQ? (Choose three.)
A. CBWFQ supports two drop methods: tail drop and WRED.
B. CBWFQ support up to 4096 dynamic queues.
C. CBWFQ provides fixed-delay guarantees.
D. If some queues do not need the bandwidth, the bandwidth is spread across the other classes.
E. CBWFQ provides fixed, minimum-bandwidth guarantees.
F. CBWFQ does not require manual traffic-classification configurations.

Correct Answer: ADE Section: (none) Explanation
Explanation/Reference:
Reference: Cisco Press – DQOS Exam Certification Guide p.273
QUESTION 102
Which configuration command applies QoS features to a particular traffic class?
A. class-map
B. traffic-map
C. policy-map
D. table-map

Correct Answer: C Section: (none) Explanation
Explanation/Reference:
Explanation:
Using policy-map command you can associate the traffic class with one or more QOS features using the
policy-map command.
Reference: Introduction to IP QoS (Course) p.8-5

QUESTION 103
When configuring CB-shaping and using shape adaptive command, how should the min-rate be configured?
A. The min-rate should be equal to or greater than the minimum bandwidth guarantee for that traffic class.
B. The min-rate should be configured to match the bandwidth configured on the physical interface.
C. The min-rate should be configured as the PIR/32 or 1500 bytes. Whichever is grater. Whichever is greater.
D. The min-rate should be configured as the CIR/8.

Correct Answer: A Section: (none) Explanation
Explanation/Reference:
Explanation:
Min-rate parameter specifies the minimum shaping rate allowed. It should be greater than the guarantee
level.

QUESTION 104
You are the network administrator at Certkiller . The newly appointed Certkiller trainee wants to know what global synchronization is. What will your reply be?
A. It is the purposeful dropping of 1 packet per TCP connection, to quickfix congestion on all TCP connections.
B. It is the process of selectively discarding TCP using packets, based on IP Precedence weighting, to reduce congestion.
C. It is the side effect of dropped packets on many simultaneous TCP connections, which causes network utilization to fluctuate between congestion state and an underutilized state.
D. It is typical of Internet performance that has been improved with advanced TCP features (i.e., Slow Start, Congestion Avoidance, and Fast Retransmit)

Correct Answer: C Section: (none) Explanation
Explanation/Reference:
Explanation:
If the receiving router drops all traffic that exceeds the queue limit, as is done by default (with tail drop),
many TCP sessions then simultaneously go into slow start. Consequently, traffic temporarily slows down to
the extreme and then all flows slow-start again. This activity creates a condition called global
synchronization.
Reference: Introduction to IP QoS p.5-5

QUESTION 105
What is the TCP measurement of the delay for a packet to get the receive and then back to the send called?
A. window size
B. transit delay
C. transit window delay
D. round-trip time
E. propagation delay
F. serialization delay

Correct Answer: D Section: (none) Explanation
Explanation/Reference:
Explanation:
Round-trip time equals a sum of all propagation, processing and queuing delay in the path.
Propagation delay is fixed, processing and queuing delay are unpredictable in best-effort networks.
Reference: Introduction to IP QoS p.7

QUESTION 106
Which of the following is valid about Low Latency Queuing (LLQ) but invalid when considering IP RTP priority?
A. It reserves and guarantees a configured amount of bandwidth.
B. It can be used for both TCP and UDP traffic types.
C. It is useful for RTP-based voice and video traffic.
D. It can match a range of UDP port numbers and provide lower latency for that traffic.
E. None of the above.
Correct Answer: B Section: (none) Explanation

Explanation/Reference:
QUESTION 107
Name two sensitivities that Voice traffic has that data traffic is not necessarily affected by. (Choose two)
A. EMI
B. RFI
C. TPI
D. Jitter
E. Delay
F. Noise

Correct Answer: DE Section: (none) Explanation
Explanation/Reference:
QUESTION 108
What are two common problems for video in the absence of QoS? (Choose two)
A. Dimmer video images.
B. Jerky video image movement.
C. Fuzzy edges on video images.
D. Unsynchronized audio and video.

Correct Answer: BD Section: (none) Explanation
Explanation/Reference:
Explanation: Today the Internet is serving a large population of all walks of life. The Internet has also grown in its service offering. Users are using the Internet to view static or dynamic information, transmit voice and video, shop, play etc. Along with these new applications of the Internet come some demands on the service(s) it provides: 1) Some applications are slow 2) Video broadcast or conferencing may have bad picture quality or appear jerky 3) Voice sessions may have bad voice quality or periods of silence 4) Critical transactions may take too long (too many seconds) 5) Bulk transfers take too long (too many hours) Reference: Introduction to IP QoS p.3
QUESTION 109
Which three are congestion management techniques according to the Cisco QoS Framework? (Choose three)
A. CQ
B. PQ
C. LLQ
D. CAR
E. NBAR
Correct Answer: ABC Section: (none) Explanation

Explanation/Reference:
Reference: Cisco Press – DQOS Exam Certification Guide p.104
QUESTION 110
What is true of LLQ but not true of IP RTP priority?
A. Reserves a configured amount of bandwidth.
B. Is useful for RTP-based voice and video traffic.
C. Can be used for both TCP and UDP traffic types.
D. Can match a range of UDP port numbers and provide lower latency for that traffic.

Correct Answer: C Section: (none) Explanation
Explanation/Reference:
QUESTION 111
Which IOS queuing features will ensure a configured amount of bandwidth to a particular class of traffic?
A. CAR
B. CQ
C. LLQ
D. WFQ
E. CBWFQ
F. PQ

Correct Answer: BCE Section: (none) Explanation
Explanation/Reference:
Explanation:
CQ provides specific percentage of bandwidth for each flow. LLQ and CBWFQ can guarantee that the flow
with the biggest priority would never starve and the bandwidth would be guaranteed it.

QUESTION 112
Which subcommand will you advice the new Certkiller trainee technician to use when configuring LLQ on a Frame Relay interface?
A. frame-relay ip rtp priority class-map
B. priority map-class
C. priority policy-map
D. frame-relay ip rtp priority interface
E. priority class-map

Correct Answer: C Section: (none) Explanation
Explanation/Reference:
Explanation:
To give priority to a class of traffic belonging to a policy map, use the priority policy-map class configuration
command. To remove a previously specified priority specified for a class, use the no form of this command.
priority{bandwidth-kbps| percent percentage} [burst]
no priority {bandwidth-kbps| percent percentage} [burst]

Reference: http://www.cisco.com/en/US/products/sw/iosswrel/ps1835/products_command_reference_chap
QUESTION 113
Which of the following statements about NBAR is true?
A. NBAR is supported on multicast enabled interfaces
B. NBAR can match up to the 512 bytes in a packet payload
C. NBAR can classify application traffic by looking beyond the the TCP/UDP port numbers of a packet
D. NBAR can be used to classify output traffic on a WAN link where tunneling or encryption is used/

Correct Answer: C Section: (none) Explanation
Explanation/Reference:
Page 185, IP Telephony Self-Study Cisco DQOS Exam Certification Guide, http//www.ciscopress.com/ title/1587200589
QUESTION 114
Which mechanism does LLQ use to support real-time traffic?
A. IP RTP
B. RED
C. CBWFQ
D. PQ

Correct Answer: D Section: (none) Explanation
Explanation/Reference:
Page 288-290, IP Telephony Self-Study Cisco DQOS Exam Certification Guide, http// www.ciscopress.com/title/1587200589
QUESTION 115
What s a drawback of the integrated services model of QoS deployment?
A. no service guarantees
B. limited scalability
C. requires complex QoS mechanisms on each router to implement the RSVP PHB
D. requires complex classification and marking of traffic at the network edge

Correct Answer: B Section: (none) Explanation
Explanation/Reference:
The main drawback of IntServ as its limited scalability.
QUESTION 116
Which two statements regarding LLQ configuration are correct? (Choose two.)
A. The bandwidth command configures the required minimum bandwidth guarantee for the low-latency traffic.
B. The bandwidth command configures the required maximum bandwidth guarantee for the low-latency traffic.
C. LLQ only supports tail-drop for the low-latency queue.
D. LLQ only supports WFQ for the low-latency queue.
E. LLQ provides strict priority queuing for CBWFQ.
F. LLQ uses a congestion-aware policer to police the maximum bandwidth guarantee.

Correct Answer: CE Section: (none) Explanation
Explanation/Reference:
Explanation: LLQ is not really a separate queuing tool, but rather a simple option of CBWFQ applied to one or more classes. CBWFQ treats these classes as strict-priority queues. In other words, CBWFQ always services packets in these classes if a packet is waiting, just as PQ does for the High queue. Reference: DQOS Exam Certification Guide p.288
QUESTION 117
DRAG DROP

A.
B.
C.
D.

Correct Answer: Section: (none) Explanation
Explanation/Reference: QUESTION 118

Which four factors must be considered when determining the pre-call bandwidth requirement for voice traffic? (Choose four.)
A. router memory size and CPU speed
B. Use NBAR to classify voice bearer and control traffic
C. Codec type
D. Packetization interval
E. Layer 2 protocol overhead
F. Bandwidth required for he voice control (signaling) traffic

Correct Answer: CDEF Section: (none) Explanation
Explanation/Reference:
QUESTION 119
Which IOS queuing mechanism allows you to place packets at the front of the queue when you have a mission critical TCP application that will only be operational with the lowest possible latency?
A. NBAR
B. CAR
C. LLQ
D. WFQ
E. CBWFQ
F. IP RTP Priority

Correct Answer: C Section: (none) Explanation
Explanation/Reference:
Explanation: The mission critical TCP application can be placed to the low-latency queue. Like PQ, the LLQ scheduler always checks the low-latency queue first, and takes a packet from that queue. If there are no packets in the low-latency queue, the normal, unpublished scheduler logic applies to the other non-low-latency queue queues, giving them their guaranteed bandwidth. Reference: Cisco Press – DQOS Exam Certification Guide p.289
QUESTION 120
Study the Exhibit below carefully:

What serial interface makes use of LLQ?
A. serial 0/0
B. serial 0/1
C. serial 0/2
D. serial 0/4

Correct Answer: D Section: (none) Explanation
Explanation/Reference:
QUESTION 121
You are the network administrator at Certkiller . The newly appointed Certkiller trainee wants to know which IOS queuing features use a strict priority queue. What will your reply be? (Choose all that apply.)
A. CQ
B. LLQ
C. CAR
D. PQ
E. NBAR F. WFQ

Correct Answer: BD Section: (none) Explanation
Explanation/Reference:
Explanation:
Both LLQ and PQ use a strict priority queue. PQ (priority queuing) is fully based on strict priorities and LLQ
uses strict priority only for its low latency queue.

QUESTION 122
What are the functions of RSVP in an Admission Control environment? (Choose all that apply.)
A. RSVP must determine if the application requesting resources is eligible.
B. RSVP must guarantee bandwidth and delay.
C. The requesting RSVP station must ensure end-to-end RSVP availability.
D. RSVP must determine the availability and adequacy of resources for the reservation.

Correct Answer: BD Section: (none) Explanation
Explanation/Reference:
Explanation:
RSVP is used for applications where bandwidth and delay related guarantees are necessary. Typical
application which use RSVP are:
-Voice over IP (Cisco phones, Microsoft NetMeeting, …)
-MPLS Traffic Engineering.
RSVP also must provide resources reservation.
Reference: Introduction to IP QoS p.7-8

QUESTION 123
Which of the factors mentioned below is important to keep in mind when selecting Call Admission Control (CAC) methods to be deployed in your network?
A. type of PBX
B. CAR
C. E.164 standards
D. network topology
E. QoS mechanisms deployed

Correct Answer: D Section: (none) Explanation
Explanation/Reference:
Reference: Page 8-76 CAC design Network Topology Considerations

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