Throughput analysis for a Video File from CDN Providers


I am doing a comparative analysis of video downloads from different CDN providers.

The same video of 848KB size is hosted in all the 3 CDN which is under study.

But after running the test, it is found as below

CDN1 : 2107KB
CDN2 : 1375KB
CDN3: 1407KB

I have attached the test result of the video download

I did download the video file to my laptop from all the three CDN URLs and found the file size is to be 848KB which is actual size.

Since the size varies, Full download time is larger for CDN1 which is larger size compared with the other two

I am wondering what are the additional data been sent from the server and how to find it

Thank you in advance