I've seen this happen over and over—not just with FDM, but other DL managers.

I start a download, and the speed looks reasonably fast, let's say 500 KB/s. Then, as I watch, the speed slowly drops. A few minutes later, it's at 50 KB/s or lower.

I'm not just talking about traffic fluctuations. It's a definite pattern I see all the time, and it can occur at any time of day or night. It seems most common with DLs from especially remote servers (e.g. other continents). So I suspect the problem isn't the originating server, but the varying number and/or quality of intermediate servers.

What I do know is, if I pause the DL, wait a few seconds, then restart it, it usually climbs back up to the fast speed. Then, after a while, it starts to drop again.

Of course it's not very practical to stand there manually pausing and resuming. So why not add this functionality to FDM?:

If download speed drops to [x] KB/s or lower, pause for 30 seconds, then resume.

However, you'd want to prevent it from being used in a trivial way. (For example, if a DL's top speed is 60 KB/s, it wouldn't make sense to pause/resume at 50.) So maybe you could say:

If download speed drops below 10% of peak speed, pause for 30 seconds, then resume.

In this case, "peak speed" would be the highest speed since the last pause (or if the DL hasn't been paused, since it was started.)

You would also want FDM to do this only with resumable DLs, so it didn't just start the same DL over and over. But I think resumable DLs are detectable, aren't they? (I notice that FDM verifies a URL before starting a DL. If a DL was not resumable, the option wouldn't appear for that DL. (You could even say "This download is not resumable" in the dialog box.)

If you're worried that this could cause some long DLs to be needlessly restarted anyway (if resumability was falsely detected?), you could say this with the option:

Warning: This download seems resumable, but resume is not guaranteed. If this download is paused and can't be resumed, it will be restarted, and this option will be deactivated for this download.

It's just an idea—but in my experience, it would make a huge difference in how long many downloads would take. And isn't that the main idea of using a DL manager? Thanks!

Thanks for the suggestion and the detailed post. We'll consider it.

Clive Sorensson wrote:Thanks for the suggestion and the detailed post. We'll consider it.

That's exciting, Clive! If it turns out to be practical, FDM will be the first DLM with such a feature (that I know of), so it would probably draw a lot of positive attention to the project.

If you do decide to code it up, I trust you'll be sure to test it under various conditions before releasing it, as I don't know if I've overlooked any important details. (Maybe some other FDM users would like to join the discussion?)

Zippy111 wrote:I've seen this happen over and over—not just with FDM, but other DL managers.
I start a download, and the speed looks reasonably fast, let's say 500 KB/s. Then, as I watch, the speed slowly drops. A few minutes later, it's at 50 KB/s or lower.

It's because of preloading… Browsers and download managers start to download before you decide about download location, download filename etc., but the timer starts only after you make your choice.

Zippy111 wrote:I'm not just talking about traffic fluctuations. It's a definite pattern I see all the time, and it can occur at any time of day or night. It seems most common with DLs from especially remote servers (e.g. other continents). So I suspect the problem isn't the originating server, but the varying number and/or quality of intermediate servers.

In such cases the problem is with flaky connection. There are no intermediate SERVERS, there are routers there, some of them may be heavily loaded or some connections may be broken during download. Packets with data may be lost or go around the world even if you connect with your neighbour using another ISP, it's unpredictable. You can use traceroute to see what's going on, but you can only change ISP to see another picture. In some cases you may use proxy as a workaround - it will be probably slower, but it may be more stable.

Zippy111 wrote:What I do know is, if I pause the DL, wait a few seconds, then restart it, it usually climbs back up to the fast speed. Then, after a while, it starts to drop again.

You mean resume, not "restart from the very beginning", right? I'm afraid it won't work as you expect. Many servers provide temporary download links. In this case you can resume download only for a limited time - maybe for a week or a day, but most possibly for an hour only.

FDM may know if the download is resumable but will NEVER know for how long it's available. If the link expires, you will probably see "404 File not found" error message. Some servers may allow to resume download when you obtain a new download link, but there's no guarantee at all.

Usher wrote:It's because of preloading… Browsers and download managers start to download before you decide about download location, download filename etc., but the timer starts only after you make your choice.

So are you saying that, for some reason, the DLM factors into the displayed speed the portion of the DL that occurred before you clicked "OK"? And that the displayed speed declines because, as the DL progresses, the pre-"OK" portion grows steadily smaller in relation to the overall DL?

But why would it do that? The displayed speed is supposed to be the current speed, not an overall average speed, right? (That's my understanding, at least.) And why would the same thing happen when you pause and resume? Does the DLM actually keep downloading while the DL is paused, so the same averaging-out effect occurs again?

Usher wrote:In such cases the problem is with flaky connection. There are no intermediate SERVERS, there are routers there...

That's right—and I'm as interested in semantics as anyone. For the purposes of this conversation, though, I think you knew what I meant. ;?)

Usher wrote:...some of them may be heavily loaded or some connections may be broken during download. Packets with data may be lost or go around the world even if you connect with your neighbour using another ISP, it's unpredictable...

I understand how data is sent a packet at a time, and that it goes through any number of transfer points (routers!) before reaching the target network. I don't know more technical details than that, though; I was simply going by my empirical observation of the speed changes, assuming they must be due to some characteristic of the infrastructure.

Zippy111 wrote:What I do know is, if I pause the DL, wait a few seconds, then restart it, it usually climbs back up to the fast speed. Then, after a while, it starts to drop again.

Usher wrote:You mean resume, not "restart from the very beginning", right? I'm afraid it won't work as you expect. Many servers provide temporary download links. In this case you can resume download only for a limited time - maybe for a week or a day, but most possibly for an hour only... FDM may know if the download is resumable but will NEVER know for how long it's available. If the link expires, you will probably see "404 File not found" error message. Some servers may allow to resume download when you obtain a new download link, but there's no guarantee at all.

Ah, right, expiring URLs—that would be a problem. I didn't think of it because the servers I've used recently have let me to pause/resume even the day after a DL started. Obviously they're not all like that, though.

Well, thanks for your time, and for the explanation!

Having said all that, I still don't quite get the speed thing.

Earlier today, I started large DL from a server on the other side of the planet. It began at over 200 KB/s. Over the next 10–15 minutes, it gradually declined until it leveled off at around 40 KB/s.

Since then, whenever I've walked by the PC, I've paused the DL, waited a few seconds, then restarted it. Each time, the DL resumes at around 40, then steadily increases back to 200, or higher. It may stay there for a couple of minutes, or for 10–20 minutes. Then it starts to decline again. Sometimes it levels off between 80–150 for 10–20 minutes, until it eventually continues dropping and returns to 40.

Are you saying all that is just an illusion—that it occurs because a certain amount of data keeps downloading during the few seconds I've paused? But even if the displayed speed is averaged out for some reason, how could such a relatively tiny amount of data affect the displayed speed for such a long period after resuming?

If I really am wasting my time with all this manual pausing/resuming, I'd be glad to know. But at this point, it still seems to be worthwhile.

And BTW, here's one of the many threads I've seen on the subject:

For people still struggling with download speed, pause/unpause DOES work

(in Reddit's r/PS4 group)

Everyone there seems to agree... Are they deluding themselves?

I don't want to go deeper in technical details, just some links what it is and how it works:
https://en.wikipedia.org/wiki/Bandwidth_management
https://en.wikipedia.org/wiki/Traffic_shaping

In short words for nontechies :
- New connections have higher priority.
- Good management won't allow to lost any connection or to leave it hungry.
- Abusers may be punished or banned.