passguide 642-642 QOS
Quality of Service Exam
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 and Japanese
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Exam Tutorial: Review type of exam questions
171. You work as a network administrator at PassGuide .com. You have deployed link efficiency mechanisms on a WAN Link. Your trainee asks you why. (Select three.)
A. decrease delay
B. decrease jitter
C. increase link speed
D. increase throughput
E. decrease propagation delay
Answer: ABD
172. The CIO of PassGuide wants to know what allows the Differential Services model to be scaled to large networking environments. What will your reply be?
A. Differential services are accomplished through hop-by-hop application signaling.
B. The Differentiated Services model scales by providing per-flow state visibility to the core of the network.
C. Policing is not utilized in the Differentiated Services model providing to facilitate efficient expediting of high priority traffic flows.
D. It achieves scalability by implementing complex classification and conditioning requirements only at network boundary nodes.
E. In the Differentiated Services model, an explicit setup mechanism predefines all QoS parameters for the packet before it is transmitted.
Answer: D
173. 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
174. Which of the following are types of scheduling used by Cisco QoS features? (Choose all that apply.)
A. Round robin
B. Modified linear
C. Strict priority
D. Fair weighted
E. Weighted Random Early Detection (WRED)
Answer: ACD
175. What is the default number of classes that Assured Forwarding (AF) have?
A. 1
B. 3
C. 4
D. 6
E. 8
Answer: C
176. Exhibit:
Central site router A has a single access link, which is a 512 Kbps link, with PVCs of CIR 256 K to each of three remote routers, namely routerB, routerC, and routerD. RouterB’s output utilization on the PVC to routerA never exceeds an average of 100 Kbps. You have verified that it never even approaches 256 Kbps, even during short burts. Which two statements are true about fragmentation? (Choose two)
A. Since there is never congestion, there is no need for fragmentation.
B. The Frame Relay network inherently deals with congestion therefore no fragmentation is required,
C. There still may be large packets leaving routerB, so fragmentation may be beneficial to overcome serialization delay.
D. Congestion delay called “Egress Blocking” could occur for frames leaving the Frame Relay network, heading for routerA, so fragmentation at all the remote routers might help some frames to be interspersed.
Answer: CD
177. For very low-speed links (those with a link speed less than 768 K), it is necessary to use techniques that provide link fragmentation and interleaving of packets. This prevents voice traffic from being delayed behind large data frames and hence bounds jitter. What are two techniques that exist for this?
A. LECS for ATM links.
B. Multilink PPP (MLP) for Serial links.
C. FRF.12 for Frame Relay.
D. 1png for DSL links.
Answer: BC
178. Exhibit:
PC1 sends a packet to R1. R1 forwards to R2, then R3, and finally R3 forwards the packet to the destination, PC2. R1 marks the packet with IP Precedence 3. Which statement is true?
A. When classifying packets at Layer 3, only Layer 3 IP Precedence marking can be used.
B. R2 and R3 can perform QoS features that ignore the marked IP Precedence field in the packet.
C. R2 and R3 can only perform QoS features based on the IP Precedence field, since the packet had already been marked.
D. R2 can apply QoS features to the packet, and R3 can on ingress, but R3 cannot apply QoS features to the packet as it exists the Ethernet port on which PC2 resides.
Answer: B
179. From the list below, what is the most important piece to implement if you are considering a VoIP infrastructure?
A. Reinstallation of the PBX.
B. QoS
C. PSTN Regeneration costs.
D. POTS installation documentation.
E. A new Help Desk trained on Voice technologies.
Answer: B
180. Which tool from the list below can be applied to the Campus Switches to help eliminate traffic congestion?
A. QoS
B. LMI
C. PIM
D. DVRMP
E. CDP
F. RDP
Answer: A
181. Command exhibit: qos pre-classify Your PassGuide .com trainee Sandra asks you what the purpose of the command displayed in the exhibit is.
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 to the outer tunnel 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
