Possible reasons for intermittent file download speeds from VPS?

Question

ubuntu

Greetings!
There is a VPS server, geographically Europe, Ubuntu Server 18.04.
I found a problem with downloading large files (starting with a few megabytes), and it appeared somehow smoothly, and now it came to this:

As you can see, the speed constantly "jumps" from zero to 5-6 MB.
Output from "nload". On the screen, I'm the only one who downloads! from RF.
Tried both http and ftp and ssh - the picture is identical.
I tried with different providers - everything is the same, only + - the speed is different.
On the server, honest 100Mb (checked fast). On the client, honest 50Mb and stable (speedtest.net and other vps).
Previously, up to 10Mb of stable was quite normal before this server.
I monitored the loading of the RAM and the processor - the RAM is usually 50-60% loaded, the percentage of the power is 10% (all threads).
Disk ssd, without downloading requests at least and nothing more loads, tk. stopped all services.
Technical support writes that there are no problems on their part and they have nothing from the category of anti-ddos and other things that could cut traffic like that.
I conclude that the problem is with the server settings. Tell me, please, in which direction to dig? What to check, where to look?

Answer 1

run mtr on both sides - check which node is losing.
try moving the VPS to another data center
>speedtest.net
it measures the speed to a specific speedtest server, which is located in a completely different location.
>Found a problem downloading large
VPN files? squid? http? ftp?
The speed of a VPN is usually different, unlike an unencrypted connection. Depends on the final route, CPU load, client/server encryption type settings, and provider tricks that can shape traffic.