Knowledge Base - FAQ

Truespeed Buffer Delay percentage

Tuesday, December 31, 2019
Submitted by ryan.grace on October 23, 2021 - 8:40pm
Question: 
How do you interpret what the buffer delay percentage means on a Layer 4 truespeed test? How is it calculated?
Answer: 
The buffer delay value represents the increase in RTT (Round Trip Time) during a TCP througput test. The formula is Average RTT during the transfer minus the baseline RTT divided by the Baseline RTT multiplied by 100. A perfect value would be 0% meaning there was no variation to the RTT during the test.  When there are retransmissions and buffer delay is high then congestion is the most likely cause. When there are retransmissions and buffer delay is low then policy enforcement (policing) is the more likely cause.

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