XPost: alt.comp.os.windows-11   
   From: dan@djph.net   
      
   On 2025-09-08, Daniel70 wrote:   
   > On 8/09/2025 10:21 pm, Dan Purgert wrote:   
   >> On 2025-09-08, Daniel70 wrote:   
   >>> [...]   
   >>> Which got me thinking ..... How do "they" Speed-test Internet Links?? ..   
   >>> particularly How do 'they' distinguish the Up-link TIME from the   
   >>> Down-link TIME?? e.g. my current speeds, using Speedtest [...]   
   >>   
   >> For the most part, a speedtest works by you downloading a file of known   
   >> size (say 100 MiB), and then sending it back.  Exact file size will vary   
   >> by testing provider, but essentially it's just this:   
   >>   
   >> Download start = 0.00   
   >> Download end = [TIME]   
   >>   
   >> File size / TIME = X Mbit / sec   
   >   
   > But how does the distant end know when I have received the entire file   
   > (i.e. Download end time)??   
      
   Because you told them you got it.   
      
      
   Rough outline is:   
      
     - You send a request to the Speedtest server to send the test file.   
     - Speedtest starts sending (START TIME HERE)   
     - (time passes)   
     - You indicate you got all the data (END TIME HERE)   
     - End minus Start equals Total Time (usually in seconds).   
     - Test File Size divided by Total Time equals Transfer Speed   
      
   This is identical to the upload test (just with roles reversed), so   
   snipped that out for brevity.   
      
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