350-401 · Question #299
350-401 Question #299: Real Exam Question with Answer & Explanation
The correct answer is B: WRED. WRED is a congestion avoidance mechanism designed to mitigate global synchronization by proactively dropping packets before queues fill completely, leading to earlier and more staggered TCP congestion window reductions.
Question
Which feature can you implement to reduce global synchronization?
Options
- Apolicing
- BWRED
- CNBAR
- Dmarking
Explanation
WRED is a congestion avoidance mechanism designed to mitigate global synchronization by proactively dropping packets before queues fill completely, leading to earlier and more staggered TCP congestion window reductions.
Common mistakes.
- A. Policing aggressively drops packets when a configured rate is exceeded, which can contribute to global synchronization if multiple flows are policed simultaneously.
- C. NBAR (Network-Based Application Recognition) is used for classifying traffic based on application and protocol, not for congestion avoidance or preventing global synchronization.
- D. Marking (e.g., DSCP or CoS) is a quality of service mechanism used to prioritize traffic, but it does not directly prevent global synchronization; it works in conjunction with other mechanisms like WRED.
Concept tested. Congestion avoidance with WRED
Reference. https://www.cisco.com/c/en/us/td/docs/ios/qos/configuration/guide/12_4t/qos_c124t_book/qos_wred.html
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