Random question about internet downloads...

[rikadik]

Why is that an internet download will typically start fast, but drop by about 80% in the first 30 seconds?

I'm sure everyone has noticed it, but why does it happen?

Today a download (over dial-up) started at 20Kbps and within 30 seconds was at 3.5Kbps.

I just don't get it!

Explain, and I will bless you.

 

[spidey07]

larger sample size equals greater accuracy.

Think about it - if you're averaging three numbers and dividing by time the inital numbers will be huge because you're going from zero to something.

 

[Nothinman]

As spidey07 says, it's most likely a calculation bug in whatever app you're downloading with. Personally, my downloads are pretty consistent as long as the server doesn't throttle me.

 

[rikadik]

Well, yes, greater sample size means greater accuracy...

But, if in the first second I've downloaded 20Kb, then the speed will say 20Kbps... which isn't wrong. If after 2 seconds I've downloaded 30Kb, the the speed will be 10Kbps at that point. As far as I'm aware its got nothing to do with sample size because it's only giving you the speed for the last second or so, and updates the speed at regular increments, so the sample size is always the same, surely?

The app I use isn't really an app at all, it's just the standard IE download thingymabob. I think I do only notice this on dial-up though, not faster connections.

Strange, and I'm sure its not a miscalculation, because you haven't convinced me that that is possible...

 

[Nothinman]

As far as I'm aware its got nothing to do with sample size because it's only giving you the speed for the last second or so, and updates the speed at regular increments, so the sample size is always the same, surely?

But what if the app isn't giving yout the speed for the last second and giving you an overall average? Meaning in the first second it downloads 20K so it says 20K/s then the next second it get 10K so it shows you 15K/s.

The app I use isn't really an app at all, it's just the standard IE download thingymabob

IE is still an app, no matter how poorly written and integrated with the OS it is.

Strange, and I'm sure its not a miscalculation, because you haven't convinced me that that is possible...

Not possible? Copy a few gigs from drive to drive with Explorer and see it tell you that there are 5342343543543 minutes remaining in the copy and tell me that's not a miscalculation.

 

[cleverhandle]

I heard somewhere that this occurs because the browser begins downloading the file as soon as you click it, while the download progress meter doesn't start until you've gone through the save-file-to dialog. So in those few seconds you're checking or entering a file name or folder, the browser gets a little headstart.

I have no idea where I heard this, nor have I ever verified it.

 

[rikadik]

But what if the app isn't giving yout the speed for the last second and giving you an overall average?

Well yeah, that would explain it, but would be a bit pointless wouldn't it? Surely the developer's saw that. If it was average it could have stopped sending information and you still think you're getting a decent speed for the next 10 minutes!

IE is still an app, no matter how poorly written and integrated with the OS it is.

Ok, it's obviously an app. I just meant it wasn't some app other than the basic. But yeah good point, does seem poorly written!

Not possible? Copy a few gigs from drive to drive with Explorer and see it tell you that there are 5342343543543 minutes remaining in the copy and tell me that's not a miscalculation.

That does indeed sound like a miscalculation. And it also indicates that the speed is not an overall average, since if it started copying very slowly for whatever reason for a moment, then that figure would occur on information gethered for that moment, and 5342343543543 minutes makes sense. Of course a huge but brief slow down wouldn't greatly affect an overall average speed.

Ok, I am making some HUGE assumptions and generalisations about how these things work. But like I said, I just want to be convinced by something.

I heard somewhere that this occurs because the browser begins downloading the file as soon as you click it, while the download progress meter doesn't start until you've gone through the save-file-to dialog. So in those few seconds you're checking or entering a file name or folder, the browser gets a little headstart.

Now that's more like it! That seems convincing. Hooray I can finally sleep at night.

 

[Nothinman]

Well yeah, that would explain it, but would be a bit pointless wouldn't it? Surely the developer's saw that. If it was average it could have stopped sending information and you still think you're getting a decent speed for the next 10 minutes!

There's plenty of pointless things in Windows. 10 minutes seems extreme, but I guess it's possible since your'e on dialup.

But like I said, I just want to be convinced by something.

The only way to know for sure is to ask MS, since they won't open source their software.

 

[rikadik]

There's plenty of pointless things in Windows.

Never a truer word spoken...

 

[thriemus]

Originally posted by: cleverhandle
I heard somewhere that this occurs because the browser begins downloading the file as soon as you click it, while the download progress meter doesn't start until you've gone through the save-file-to dialog. So in those few seconds you're checking or entering a file name or folder, the browser gets a little headstart.

I have no idea where I heard this, nor have I ever verified it.

This is correct