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- CCNA Routing and Switching 200-125
76.
Which is a correct statement about device trust boundary for QoS?
- A.The trust boundary should always be an asset IT controls
- B.The switch should always be set as the trust boundary.
- C.Only routers can create trust boundaries.
- D.Only IP phones can become trust boundaries.
- Answer & Explanation
- Report
Answer : [A]
Explanation :
Explanation :
| A malicious user can mark all of his or her traffic as high priority. Therefore, a trust boundary must be established by the network administrator. A common trust boundary device is the IP phone, but it is any device that is in control of the network administrator. |
77.
Which layer 3 protocol is used for marking packets with QoS?
- A.DSCP
- B.802.1Q
- C.CoS
- D.QoE
- Answer & Explanation
- Report
Answer : [A]
Explanation :
Explanation :
| The Differentiated Services Code Point (DSCP) is a 6-bit value in the Type of Service (ToS) field of the IP header. The DSCP value defines the importance of packets at layer 3. |
78.
Which technology is used to identify and mark applications such as Bittorrent and
Netflix for QoS?
- A.ACLs.
- B.Routing tables
- C.NBAR2
- D.Tail drop
- Answer & Explanation
- Report
Answer : [C]
Explanation :
Explanation :
| Network Based Application Recognition version 2 is used to classify applications based on a Protocol Description Language Module (PDLM). |
79.
What is the measurement of packets discarded due to congestion of queues?
- A.Bandwidth
- B.Delay
- C.Jitter
- D.Loss
- Answer & Explanation
- Report
Answer : [D]
Explanation :
Explanation :
| Loss is the measurement of discarded packets. The measurement is a percentage of transmitted packets. For example, if 100 packets are transmitted and 3 packets are dropped, then the loss is 3%. Loss can be attributed to congestions, faulty wiring, EMI, or device queue congestion. |
80.
Which is a true statement about the Class of Service field?
- A.The Class of Service field is a layer 3 field.
- B.The Class of Service field is only present in 802.1Q frames.
- C.The Class of Service field is present from end to end of a transmission.
- D.The Class of Service field is 6 bits.
- Answer & Explanation
- Report
Answer : [B]
Explanation :
Explanation :
| The Class of Service field is only found in layer 2 transmissions, specifically only across trunks due to the dependency of 802.1Q. The CoS field is a 3-bit field in the 802.1Q frame type |
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