Real-time rate limiting on the service ingress is a feature that performs_____________. Traffic above the defined PIR is ______________.

Question

Options

• APolicing, expedited
• BMetering, marked discard eligible
• CMarking, marked discard eligible
• DPolicing, discarded
• EShaping, discarded

• A
  4% (1)
• B
  4% (1)
• C
  12% (3)
• D
  76% (19)
• E
  4% (1)

Explanation

Option D is correct because real-time rate limiting at the service ingress is a policing function - it enforces a hard rate limit by discarding any traffic that exceeds the defined Peak Information Rate (PIR), with no buffering or queuing involved.

Why the distractors are wrong:

• A (Policing, expedited) - gets the function right but is wrong on the outcome; excess traffic is dropped, not prioritized or expedited.
• B (Metering, marked discard eligible) - metering only measures traffic rates; it does not enforce or act on them. "Marked discard eligible" applies to marking schemes (like DE bit in Frame Relay), not hard ingress policing.
• C (Marking, marked discard eligible) - marking changes QoS/DSCP fields on packets for downstream treatment; it is not an enforcement mechanism and doesn't describe rate limiting behavior.
• E (Shaping, discarded) - shaping buffers excess traffic and releases it smoothly; it does not discard. Shaping also typically occurs on egress, not ingress.

Memory tip: Think "Police = Punish" - a police officer at the door (ingress) stops rule-breakers immediately by turning them away (discard). A shaper is more like a bouncer with a waiting room (buffer). If it's real-time and at the entrance, it's policing, and offenders get dropped.

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