4.7 Explain the Forwarding Per-Hop Behavior (PHB) for QoS Such as Classification, Marking, Queuing, Congestion, Policing, and Shaping 200-301 Practice Questions (Page 4)

Questions 16–20

1. 16foundation · easy

   A network engineer needs to identify voice traffic on an interface so that it can receive a specific QoS treatment. Which action is performed during the classification step of QoS?

   • ACategorizing packets based on criteria such as DSCP or ACLs
   • BDropping packets that exceed a configured rate
   • CAssigning a DSCP value to voice packets
   • DPlacing packets into different output queues
   Reveal Solution Discussion Select an answer first
2. 17expert · hard

   A network engineer is configuring QoS on a router that connects to a service provider. The provider requires that all traffic be marked with a DSCP value that reflects the service level. The engineer has two options: trust the DSCP markings from the customer edge router, or re-mark all traffic based on the customer's contract. The customer edge router is known to sometimes send traffic with incorrect DSCP values. Which approach should the engineer take to ensure consistent service level enforcement?

   • ATrust the DSCP markings from the customer edge router.
   • BRe-mark all traffic based on the customer's contract.
   • CRe-mark only traffic that has an invalid DSCP value.
   • DTrust the DSCP markings but police all traffic to the contracted rate.
   Reveal Solution Discussion Select an answer first
4. 18application · medium

   A packet travels from a customer router through two ISP routers to a destination. The customer router marks the packet with DSCP EF. The first ISP router is configured to trust the DSCP marking and forward the packet accordingly. The second ISP router is configured to re-mark all traffic to DSCP AF11. What is the per-hop behavior (PHB) of the packet at the second ISP router?

   • AThe packet is re-marked to DSCP AF11 and forwarded according to AF11 PHB.
   • BThe packet is forwarded with DSCP EF because the second router trusts the first router's marking.
   • CThe packet is dropped because the DSCP was changed.
   • DThe packet is forwarded with DSCP EF because the first router trusted it.
   Reveal Solution Discussion Select an answer first
5. 19foundation · easy

   What is a key characteristic of policing in QoS?

   • AIt introduces delay for excess traffic
   • BIt buffers excess traffic to smooth bursts
   • CIt always increases the transmission rate
   • DIt drops or re-marks excess traffic without buffering
   Reveal Solution Discussion Select an answer first
6. 20application · medium

   A company has a 10 Mbps WAN link to its headquarters. The marketing department frequently sends large file transfers that cause bursts of traffic exceeding 10 Mbps, leading to packet loss. The network team wants to smooth out these bursts to avoid packet loss while still allowing the marketing traffic to be sent eventually. Which mechanism should be used?

   • AShaping the marketing traffic to a rate of 10 Mbps with a burst size.
   • BUsing tail drop on the interface.
   • CPolicing the marketing traffic to a rate of 10 Mbps with a drop action.
   • DUsing WRED on the interface.
   Reveal Solution Discussion Select an answer first