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This product reached the end of support date on March 31, 2021.

regarding the dummy images for the bandwidth calculation.

szxhchen
Participant

Hi,

Regarding the bandwidth,as we know,in order to calculate the time it takes to download resources, the JavaScript Agent must measure the actual bandwidth. To accomplish this it requests maximum of 6 dummy images of increasing size (3 kbyte - 1 Mbyte) until an image download takes at least 100 milliseconds. My question is why the 30/100/300kbyte images were download as we can calculate that the bandwidth is about 56k/sec so that it will take more than 100 milliseconds while download the 3kbyte image.Please see the screenshot I attached. Thanks.

6 REPLIES 6

paul_johnson
Dynatracer
Dynatracer

Can you please post the version of AppMon that you are using
Thanks

Paul

dynaTrace Server version '6.2.16.1014'. Thank you.

Xiaohe

david_n
Inactive

Hello xiaohe,

According to the documentation, there is an initial image that is sent to calculate the latency of your network. After that, the JS agent will send the remaining messages subtracting the latency in order to calculate the bandwidth. Due to the latency subtraction, the DT server might have recorded the times for 30/100/300kbyte images at less than 100ms.


  • First (0k) image is used for latency calculation, which will be subtracted from all other measurements
  • All subsequent images will be loaded until the download time without latency exceeds 100ms

https://community.dynatrace.com/community/display/DOCDT65/JavaScript+Agent

Thanks,

David Nicholls

szxhchen
Participant

Hi David,

Thanks for your answer.

We can see the that it took 5.51/16.53/41.76 seconds respectively to download the 30/100/300 kbyte images which greatly exceeds 100ms. So it must take more than 100ms to download the 3kbyte image.

Thanks,

xiaohe

paul_johnson
Dynatracer
Dynatracer

Hi Xiaohe

I have reproduced this issue and raised an internal ticket for it. I am working on a solution.

Paul

paul_johnson
Dynatracer
Dynatracer

A fix has been applied to all AppMon versions from 6.2.x onwards, the fix is now in the process of being tested.