350-501 Automation and Quality of Service Practice Question
Which congestion avoidance technique drops packets probabilistically before the queue becomes full?
⚠ Common exam trap
Candidates often confuse congestion avoidance (WRED) with congestion management (queuing algorithms like PQ, CQ, or FIFO), mistakenly thinking that any queuing mechanism that drops packets qualifies as congestion avoidance.
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
✓
WRED
WRED (Weighted Random Early Detection) is a congestion avoidance mechanism that monitors the average queue depth and, when it exceeds a configured threshold, begins dropping packets probabilistically before the queue becomes completely full. This proactive dropping signals TCP senders to reduce their transmission rates, thereby preventing tail drop and global synchronization.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
FIFO
Why it's wrong here
FIFO drops only when queue is full.
- ✗
Priority Queuing
Why it's wrong here
Priority Queuing is a scheduling mechanism.
- ✓
WRED
Why this is correct
WRED proactively drops packets to avoid congestion.
- ✗
Custom Queuing
Why it's wrong here
Custom Queuing is a scheduling mechanism.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 350-501 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 350-501 exam.