READ Free Dumps For Cisco- 400-101
Question ID 18529 | Which congestion-avoidance or congestion-management technique can cause global
synchronization?
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Option A | Tail drop
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Option B | Random early detection
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Option C | Weighted random early detection
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Option D | Weighted fair queuing
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Correct Answer | A |
Explanation Explanation: Tail Drop Tail drop treats all traffic equally and does not differentiate between classes of service. Queues fill during periods of congestion. When the output queue is full and tail drop is in effect, packets are dropped until the congestion is eliminated and the queue is no longer full. Weighted Random Early Detection WRED avoids the globalization problems that occur when tail drop is used as the congestion avoidance mechanism on the router. Global synchronization occurs as waves of congestion crest only to be followed by troughs during which the transmission link is not fully utilized. Global synchronization of TCP hosts, for example, can occur because packets are dropped all at once. Global synchronization manifests when multiple TCP hosts reduce their transmission rates in response to packet dropping, then increase their transmission rates once again when the congestion is reduced. Reference: http://www.cisco.com/c/en/us/td/docs/ios/12_2/qos/configuration/guide/fqos_c/qcfconav.ht ml#wp1002048
Question ID 18530 | Which three features require Cisco Express Forwarding? (Choose three.)
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Option A | NBAR
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Option B | AutoQoS
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Option C | fragmentation
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Option D | MPLS
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Option E | UplinkFast
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Option F | BackboneFast
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Correct Answer | A,B,D |
Explanation Explanation: QoS Features That Require CEF These class-based QoS features are supported only on routers that run CEF. Network Based Application Recognition (NBAR) provides intelligent network classification. For more information, refer to Network Based Application Recognition. The AutoQoS -VoIP feature simplifies and speeds up the implementation and provisioning of QoS for VoIP traffic. This feature is enabled with the help of the auto qos voip command. CEF must be enabled at the interface or ATM PVC before the auto qos command can be used. For more information about this feature and its prerequisites, refer to AutoQoS - VoIP. From MPLS Fundamentals - Luc De Ghein Why Is CEF Needed in MPLS Networks? Concerning MPLS, CEF is special for a certain reason; otherwise, this book would not explicitly cover it. Labeled packets that enter the router are switched according to the label forwarding information base (LFIB) on the router. IP packets that enter the router are switched according to the CEF table on the router. Regardless of whether the packet is switched according to the LFIB or the CEF table, the outgoing packet can be a labeled packet or an IP packet Reference: http://www.cisco.com/c/en/us/support/docs/asynchronous-transfer-mode- atm/ip-to-atm-class-of-service/4800-cefreq.html