Click the exhibit button below. Given the scheduler-policy (below), which of the following can be done to guarantee that the best-effort traffic receives its configured CIR value?

Question

Exhibit

Options

• AChange the CIR-level value for the best-effort queue to 8.
• BDo not change anything; it is already guaranteed to receive its CIR
• CChange the CIR-level value for the best-effort queue to 1.
• DChange the CIR-weight value of the AF queue to 0.

• A
  55% (24)
• B
  30% (13)
• C
  16% (7)

Explanation

In this scheduler-policy scenario, the best-effort queue fails to receive its configured CIR because it competes at the same CIR-level as the AF (Assured Forwarding) queue, which has a non-zero CIR-weight that can consume available bandwidth. Option A resolves this by moving the best-effort queue to CIR-level 8, placing it at a distinct scheduling level where it is no longer in competition with the AF queue for CIR bandwidth. Option D resolves it differently - setting the AF queue's CIR-weight to 0 removes AF from the CIR scheduling competition entirely, leaving best-effort to receive its full configured CIR unopposed.

B is wrong because the existing configuration does not guarantee best-effort its CIR - that's the very problem being solved. C is wrong because setting the best-effort queue to CIR-level 1 does not eliminate competition; if the AF queue shares or has priority at that level, best-effort can still be starved of its CIR.

Memory tip: Think "separate or eliminate" - you either separate the queues into different CIR-levels (A) so they don't compete, or you eliminate the competitor's weight (D) so it can't consume shared CIR bandwidth. Any answer that leaves active competition at the same level in place cannot guarantee CIR delivery.

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