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

A network administrator notices that bursty data transfers sent across a 100 Mbps physical interface to a service provider are experiencing heavy packet loss. The service provider enforces a strict 20 Mbps Committed Information Rate (CIR) using a policer at their ingress edge. Which Quality of Service (QoS) mechanism should the administrator configure on the local router's egress interface to prevent provider-side packet drops by smoothing out the traffic rate?

  1. Traffic shaping to buffer out-of-profile packets in memory and release them at a steady rate matching the contracted limit.Answer
  2. B
    Traffic policing to store non-conforming packets in a dynamic queue until interface bandwidth becomes available.
  3. C
    Low Latency Queuing (LLQ) to strictly prioritize all bursty data packets over control traffic.
  4. D
    Class-Based Weighted Fair Queuing (CBWFQ) to drop lower-priority data packets locally before they reach the provider line.

Answer

Traffic shaping to buffer out-of-profile packets in memory and release them at a steady rate matching the contracted limit.
Traffic shaping is designed to rate-limit outbound traffic to a contracted Committed Information Rate (CIR) by buffering bursts in memory and transmitting packets continuously at a steady rate. This prevents the provider's ingress policer from seeing rate spikes and dropping packets.

Step-by-Step Solution

1
Analyze the problem scenario and bandwidth mismatch.
The local physical interface sends traffic at 100 Mbps, but the service provider polices incoming traffic at 20 Mbps.
Bursty transmissions exceeding 20 Mbps cause the provider's policer to drop excess packets immediately.
2
Compare Quality of Service traffic conditioning mechanisms (Policing vs. Shaping).
Traffic policing drops/remarks excess packets without queuing, whereas traffic shaping buffers excess packets in memory queues to smooth out micro-bursts.
To avoid packet loss while adhering to a sub-rate CIR on a faster physical link, outbound traffic must be shaped.
3
Select the appropriate egress QoS tool.
Configure egress traffic shaping targeting the 20 Mbps rate.
Shaping smooths egress burstiness, holding out-of-profile packets in a queue rather than letting the provider's policer discard them.

Key Concept

Differences in operational mechanics between QoS Traffic Policing and Traffic Shaping
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Topics

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

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