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

A network engineer is configuring Quality of Service (QoS) mechanisms on a Cisco router interface to control bandwidth usage. Which two behaviors are characteristic of traffic policing rather than traffic shaping? (Select two.)

  1. Dropping excess packets immediately when traffic exceeds the configured rate limitAnswer
  2. Remarking the DSCP or CoS values of out-of-profile traffic to lower priority valuesAnswer
  3. C
    Buffering excess packets in interface queues to smooth out traffic bursts for later transmission
  4. D
    Applying queuing delays to ensure traffic fits within a configured egress shaper profile

Answer

Traffic policing is characterized by dropping excess packets immediately when traffic exceeds the rate limit and remarking DSCP or CoS values of non-conforming packets.
Traffic policing enforces a hard rate limit by either dropping out-of-profile packets immediately or remarking their QoS headers (such as DSCP or CoS) to a lower priority class so they can be dropped downstream if congestion occurs.

Step-by-Step Solution

1
Identify the key operational difference between policing and shaping
Policing acts on instantaneous traffic rates (inbound or outbound) by either dropping or remarking non-conforming packets.
Policers do not use memory buffers to hold excess traffic, whereas shapers buffer traffic to smooth bursts.
2
Evaluate the choices based on policing mechanics
Immediate packet drops and packet remarking are valid policing actions. Buffering packets and adding queuing delay describe shaping.
Shaping retains packets in a queue to smooth egress rate, while policing enforces strict rate boundaries.

Key Concept

Traffic Policing vs. Traffic Shaping Mechanics
Estimated Time:45s
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Topics

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

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