350-501 Architecture Practice Question
A service provider has deployed QoS on its MPLS backbone to offer different classes of service. The provider notices that EF (Expedited Forwarding) traffic sometimes experiences high jitter during congestion. Following recommended practices, which action is MOST likely to reduce jitter for EF traffic?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use priority queuing (LLQ) for EF traffic with a policer
Priority queuing (LLQ) with a policer ensures EF traffic is served strictly before other queues, reducing jitter, while the policer prevents EF traffic from monopolizing bandwidth. Option B is wrong because traffic shaping smooths bursts but does not provide priority treatment during congestion, so jitter can still occur. Option C is wrong because changing DSCP to AF41 would reclassify EF traffic to a lower priority class, potentially increasing jitter and delay. Option D is wrong because WRED is a congestion avoidance mechanism that drops packets randomly, which can cause jitter for EF traffic; EF should be exempt from WRED.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Use priority queuing (LLQ) for EF traffic with a policer
Why this is correct
LLQ gives strict priority, minimizing jitter by servicing EF first.
- ✗
Apply traffic shaping on all EF packets at the edge
Why it's wrong here
Shaping smooths bursts but does not eliminate jitter under congestion; priority queuing is better.
- ✗
Change the DSCP value of EF traffic to AF41 to reduce drops
Why it's wrong here
Changing DSCP does not address jitter; proper queuing is required.
- ✗
Apply weighted random early detection (WRED) on the EF queue
Why it's wrong here
WRED might drop EF packets, causing retransmissions and jitter; not recommended for EF.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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