729628 - download time and KB/sec innacurate

Status: RESOLVED INVALID

(Firefox :: Untriaged, defect)

Description

[Dr. Sassafras]

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:10.0) Gecko/20100101 Firefox/10.0
Build ID: 20120129021758

Steps to reproduce:

Download several identical files from different servers, simultaneously. 


Actual results:

The minutes remaining and KB/sec and amount completed all show. However on some files, you can see that the file is downloading twice as fast (say the one file has downloaded 10mb and the other one has download 20mb. However if you look at the KB/sec or the time to completion, they will say that the one that is downloading much slower is the faster one. I have seen this many time over two different machines.

To clarify. The one with the faster KB/sec, which is in fact downloading much more slowly according to the amount downloaded should be reading a different kb/sec and should have a different time to completion on it. 

This only happens with certain servers or perhaps ways serves deliver files. What I have noticed is that it does happen when the faster one takes regular "pauses" micro pauses, for a second or less, or more. The download appears to come in spurts (according the the amount downloaded)

My own thought is that firefox is taking a calculation of how fast the download is coming in from the server, and only calculates the (high speed)?, it does not take the pauses into account. The time to completion must be a simple formula of kb/sec and the size of the file, but in reality the kb/sec is not a reality. Its a mystical number that has been created from some faulty algorithm. 


Expected results:

Instead of using the current algorithm for kb/sec and then making a calculation for how long the file will take to complete at the listed size, a calculation needs to be made for how long the file has been download for, how much has been downloaded and how much still needs to be downloaded. This could be done over a period of seconds long enough to account for ups and downs but short enough to give current and up to date information.

In any case, its always best to come down the the phonon, in this case the actual download size. extrapolating from download speed instead of the amount of data being stored is perhaps more prone to errors like this.

Currently Rapidshare has been giving lots of pauses. You can download files from rapidshare and see for yourself. Reproducible.

Comment 1

[Kieran Clancy]

I can confirm this with Firefox 10.0.1 on Linux.

The summary above seems to be a long way of saying the following:

"Rapidshare sends files at 100KB/s for a second or so, then pauses for a few seconds. Firefox continues to report the speed at 100KB/s even though it's usually a fraction of that. Furthermore, it grossly underestimates the time remaining."

The main bug here is that if a server stops sending packets, Firefox seems to stop updating the speed in the display (so it just stays at 100KB/s, for example). If it dropped down to 0KB/s during the few seconds the data stopped being sent, the user wouldn't be given a false impression of the speed.

Firefox should update the speed in the display at least once or twice a second even if no new data has come in.

A secondary bug is that the calculation of time remaining uses too short a time window. It's fine to use a short window for displaying the "current speed", but ideally Firefox should use an exponentially weighted moving average of the speed over a longer period (e.g. 10-20 seconds) to calculate the time remaining.

Comment 2

[Dr. Sassafras]

I have additionally found that on rapidshare, the phenomenon only occurs when a DSL connection is used, cable does not produce this effect. Files download at full speed over a Cable connection, and on DSL for some reason they are highly choked. Firefox seems to display the time the file would have downloaded if it were not choked. (Ontario Canada)

Comment 3

[Liviu Cirdei]

Is this still an issue on latest Firefox versions? e.g. Firefox 43 / Nightly 46. I observed Firefox no longer displays the KB/s when downloading a file. It only shows the time remaining and the file size progress. So I am tempted to mark this as Resolved, but I kindly ask for your confirmation first.

Comment 4

[Dr. Sassafras]

Your right, KB/s is no longer shown. This can no longer be an issue.

On another note, I'm wondering now if it had something to do with bad packets being generated from a common router of the day, with FF providing insufficient error checking.... One mystery that will never be solved. Oah well.