H12-821_V1.0 · Question #760
An additional packet loss strategy uses the tail drop (Tail-Drop) method. This drop method will cause the TCP global synchronization rate.
The correct answer is A. TRUE. Tail Drop does indeed cause TCP global synchronization, making option A correct. When a router's queue fills up using tail drop, it drops packets from multiple TCP flows simultaneously. All affected flows detect the loss at roughly the same time, reduce their congestion windows…
Question
Options
- ATRUE
- BFALSE
How the community answered
(30 responses)- A77% (23)
- B23% (7)
Explanation
Tail Drop does indeed cause TCP global synchronization, making option A correct. When a router's queue fills up using tail drop, it drops packets from multiple TCP flows simultaneously. All affected flows detect the loss at roughly the same time, reduce their congestion windows in unison, then ramp back up together - creating synchronized waves of congestion and idle bandwidth that repeat cyclically.
Why B is wrong: TCP global synchronization is a well-documented, real phenomenon specifically associated with tail drop. Denying it contradicts established networking behavior and the reason why more sophisticated AQM (Active Queue Management) methods like RED (Random Early Detection) were developed.
Memory Tip: Think of tail drop as a traffic light that turns red for everyone at once - all cars (TCP flows) slam the brakes simultaneously, then all accelerate together, causing rhythmic "waves" of congestion. RED/WRED fixes this by randomly tapping individual brakes before the queue is full, staggering the slowdowns.
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