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Difficulty: MediumQoS Per-Hop Behaviors, Classification, Marking, Queuing, and Traffic Shaping/Policing

An enterprise network administrator is implementing Quality of Service (QoS) traffic conditioning mechanisms on WAN edge routers. Which two statements correctly describe the operational differences between traffic policing and traffic shaping? (Select two.)

  1. Traffic policing can be configured on both ingress and egress interfaces to drop or remark packets that exceed the specified target rate.Answer
  2. Traffic shaping uses memory queues to temporarily buffer bursty traffic exceeding the configured rate, smoothing outbound traffic flow on egress interfaces.Answer
  3. C
    Traffic policing holds out-of-profile packets in hardware memory queues until link bandwidth becomes available, avoiding packet drops.
  4. D
    Traffic shaping is applied on ingress interfaces to drop bursty traffic before packets enter the router internal switching fabric.

Answer

The two correct statements are that traffic policing can be applied to both ingress and egress interfaces to drop or remark packets exceeding the target rate, and traffic shaping uses queues on egress interfaces to temporarily buffer bursty traffic and smooth outbound delivery.
Traffic policing and shaping handle non-conforming traffic differently. Policing functions on both ingress and egress directions by dropping or remarking excess packets without buffering. In contrast, shaping is supported strictly on egress interfaces, utilizing memory queues to buffer bursty traffic and smooth outbound flow.

Step-by-Step Solution

1
Evaluate the directional capability and packet handling mechanism of traffic policing.
Policing operates in both ingress and egress directions without buffering, handling excess traffic instantaneously by dropping packets or remarking DSCP/CoS values.
Policing enforces rate boundaries without introducing queuing delay.
2
Evaluate the directional capability and packet handling mechanism of traffic shaping.
Shaping applies strictly to egress traffic and utilizes memory queues to buffer excess packets, smoothing bursts to fit within a configured rate.
Shaping prevents packet drops during brief bursts at the expense of potential queuing delay and jitter.

Key Concept

QoS Traffic Conditioning: Policing vs Shaping Operational Mechanics
Estimated Time:1m 30s
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Topics

QoS Per-Hop Behaviors, Classification, Marking, Queuing, and Traffic Shaping/Policing

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