1
When I run multiple large file transfers over TCP (direction and upper protocol does not matter, it for example works similarly on HTTPS and FTPS) on Linux machine (but Windows works the same way) the speed is splitted into multiple paralel uploads/downloads (for example 2 transfer, 5 MiB/s per each). But when the last upload remains the speed of that last upload does not grow (to 10 MiB/s in example) but it stays at the level when bandwidth was splitted (5 MiB/s in example) into multiple uploads/downloads and only manualy reseting the transfer will cause to transfer data faster (aprox. 10 MiB/s).
Is there any way to force last transfer to be faster without interupting it?
My gues is that it is caused by stabilized TCP window but I don't know how to verify it and how to force Linux to enforce extension of that window.
Misaz
Posted 2020-01-13T16:14:53.187
Reputation: 426
What is the network setup? (there are a few scenarios where this would be expected) – Smock – 2020-01-13T16:25:10.397
There are two network setups and the behaviour is the same. 1st setup is computer (Linux or Windows does not matter, but linux specific ansers are prefered) connected to the internet downloading multiple file via HTTPs. 2st setup is transfer in local network. There are computer and server which acts as remote target server from setup 1. There are no restrictions (at least on my side) in the network. It is gigabit based network and speeds in question are only examples. – Misaz – 2020-01-13T16:34:39.193
What sort of "Internet"? DSL? Fiber? Satellite? Cable? Cellular? Each type of connection can have different causes. – TheCompWiz – 2020-01-13T20:00:13.857
in my case it is cable but the issue is not internet dependent. You can try it yourself. Start downloading two debians from https://cdimage.debian.org/debian-cd/current/amd64/iso-cd/ and see the speeds. Bit later cancel one downloading and see how long will it take to second (non-canceled) download to achieve a full bandwidth which was freed by cancel.
– Misaz – 2020-01-13T20:42:09.203Have you tried downloading from 2 different locations and then cancelling one? There may be a bandwidth limit per connection on their end. (I downloaded two different iso's from here and i was getting 1.5 MB/s, until I cancelled and then I was getting 3 MB/sec.) Wait, are you uploading or downloading or both? Are you comparing two transfers of the same direction? 2 downloads.
– Smock – 2020-01-14T09:38:01.103Also - quite often the speed you see is an average over the whole time of the download/upload. so if you've had 2 downloads going for 1 hour, and one finishes 5 minutes before the other, you won't see much difference in avg speed – Smock – 2020-01-14T09:42:18.283
I am comparing two (or more but it does not matter) transfer of the same direction (no matter which one). I think the speed is current because the estimated time to complete reflect it. – Misaz – 2020-01-14T10:23:09.427