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QUESTION 51
How does Packet Loss Concealment improve voice quality?
A. Cisco Packet Loss Concealment technology decreases the voice sampling rate to 10 ms of the voice payload to smooth gaps in the voice stream.
B. Packet Loss Concealment intelligently analyzes missing packets and generates a reasonable replacement packet to improve the voice quality.
C. Packet Loss Concealment will buffer 20 to 50 ms of a voice stream to minimize lost or out-of- order voice packets.
D. Packet Loss Concealment will compensate for packet loss rates between 1 and 5 percent by generating a reasonable replacement packet to improve the voice quality.
Correct Answer: B Section: (none) Explanation
Explanation/Reference: Explanation:
Packet loss concealment is a technology designed to minimize the practical effect of lost packets in VOIP. PLC mitigates against the effects of packet loss, which is the failure of one or more transmitted packets to arrive at their destination, by artificially regenerating the packet received prior to the lost one, followed by insertion of the duplicated packet into the gap. The digital value of the dropped packet is estimated by interpolation and an artificially generated packet inserted on that basis.
http://www.cisco.com/en/US/partner/tech/tk652/tk698/technologies_tech_note09186a00800f6cf8.s html
QUESTION 52
When a Cisco Unified Border Element connects two VoIP streams using flow-around media, which of the following options describes the components of the call that flow around and the components that flow through the device?
A. All security information flows through the Cisco Unified Border Element, and all call signaling and RTP flows around the device.
B. Call signaling flows through and call media flows around the device.
C. Call media flows through and call signaling flows around the device.
D. The initial call-signaling traffic flows through the device to initiate the call and then all subsequent calls flow around the device.
Correct Answer: B Section: (none) Explanation
Explanation/Reference:
Explanation:
QUESTION 53
Refer to the exhibit. What will the class map do if a packet arrives that is marked with a CoS of 6 and a DSCP value of EF?
A. The class map will match the packet and forward it to the policy map to be marked.
B. The class map will not map the packet and no QoS will be applied
C. The class map will wait for the next packet in the stream to see if it has a CoS marking of 5 and then forward both packets to the policy map.
D. For the packet to be forwarded to the policy map, it must have either a CoS of 5 or a DSCP value of EF.
Correct Answer: B Section: (none) Explanation
Explanation/Reference: Explanation:
If there is no match for a packet, no QoS processing occurs on the packet and the switch offers best-effort service to the packet.
http://www.cisco.com/en/US/docs/switches/lan/catalyst2960/software/release/12.2_25_see/config uration/guide/swqos.html
QUESTION 54
Refer to the exhibit. Consider an outgoing call that is being placed in all three scenarios that are shown in the exhibit. What is the result of the call, going down the table from top to bottom?
A. success, success, success
B. success, success, fail
C. success, fail, success
D. success, fail, fail
E. fail, success, success
F. fail, success, fail
Correct Answer: A
Section: (none)
Explanation
Explanation/Reference:
Explanation: Various combinations of COR lists and the results are shown in this table:
http://www.cisco.com/en/US/tech/tk652/tk90/technologies_configuration_example09186a008019d 649.shtml
QUESTION 55
Refer to the exhibit. When an international call to 90114989531212001 is placed from extension 2001, which of the following statements is true?
A. The call will fail because no incoming COR list is applied.
B. The call will succeed because the incoming COR list is a superset of the outgoing COR list.
C. The call will fail because the incoming COR list is not a superset of the outgoing COR list
D. The call will succeed because the incoming COR list has the highest priority, by default, when no incoming COR list is applied.
Correct Answer: D Section: (none) Explanation
Explanation/Reference: Explanation:
By default, an incoming call leg has the highest COR priority and the outgoing COR list has the lowest COR priority. This means that if there is no COR configuration for incoming calls on a dial-peer, then you can make a call from this dial-peer (a phone attached to this dial-peer) going out of any other dial-peer, irrespective of the COR configuration on that dial-peer.
http://www.cisco.com/en/US/tech/tk652/tk90/technologies_configuration_example09186a008019d 649.shtml
QUESTION 56
Calculate how many IP phone calls can be sent across a 64 kbps Frame Relay link that uses the
A. 729 codec being sampled 50 times a second, 20 bytes a sample, and has 6 bytes of Frame Relay header overhead with no checksum and uses header compression.
B. 3
C. 4
D. 5
E. 7
Correct Answer: C Section: (none) Explanation
Explanation/Reference:
Explanation:
QUESTION 57
Which three methods are used by a Cisco Unified Border Element to provide network hiding? (Choose three.)
A. Back-to-back user agent, replacing all H.323-embedded IP addressing
B. IP network security boundary
C. Media flow-through
D. RSVP
E. IP network privacy and topology hiding
F. Intelligent IP address translation for RTP flows
Correct Answer: BCE Section: (none) Explanation
Explanation/Reference:
Explanation:
QUESTION 58
Which of the following describes SIP Early Offer?
A. In SIP Early Offer mode, the SDP media capabilities are sent in the INVITE message of the calling device.
B. SIP Early Offer always uses session indicator 183.
C. In SIP Early Offer mode, the SDP media capabilities are sent in the 200 OK messages of the “Pass Any Exam. Any Time.” – www.actualtests.com 39 Cisco 642-437 Exam calling device.
D. In SIP Early Offer mode, the INVITE and the 200 OK messages use non-SDP message format to indicate SIP Early Offer
Correct Answer: A Section: (none) Explanation
Explanation/Reference:
Explanation:
QUESTION 59
Voice packets are arriving at a destination with a variance of between 20 and 50 milliseconds. If the jitter buffer has a capacity of 30 milliseconds, what is the impact on the audio at the receivers IP phone?Voice packets are arriving at a destination with a variance of between 20 and 50 milliseconds. If the jitter buffer has a capacity of 30 milliseconds, what is the impact on the audio at the receivers IP phone?
A. The jitter buffer will replay the previous voice packets to replace those packets that exceed 30 milliseconds to avoid speech gaps.
B. There will be no impact the audio stream because the audio packets are arriving in the jitter buffer window.
C. The DSP will automatically increase the jitter buffer size after sampling the range of incoming voice packets to accommodate the wider range in variation of voice packet arrival times to avoid voice gaps.
D. The IP phone will negotiate in mid-call a lower bandwidth codec to reduce the delay in the arrival of voice packets to avoid voice gaps.
Correct Answer: B Section: (none) Explanation
Explanation/Reference:
Explanation:
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