qBittorrent official forums

Hi,

Is it possible to set alternate upload speed when not downloading?

Screenshot of the feature in uTorrent:
http://i.imgur.com/4ovLnP7.png

Why?

It is a pretty useless setting that really does not do much (if anything) to manage data transfer OR "improve speeds" despite what innumerable "Speed up uTorrent" videos on YouTube claim.

It is one of these settings that may seem to make sense, but in reality they don't, it simply makes the client work a little 'harder' for no real tangible benefit. Up/Down data runs on separate channels of the copper and fibre medium that connects you to the Internet, so they don't actually occupy the same 'space' or 'bandwidth'. simply increasing upload rate just because there is minimal download occurring is not going to have any effect.

Yes, you're right that the mediums are separate. They're split, but if you have an upload that's completely saturating your connection, due to the nature of TCP, your syn/acks will be delayed due to the upload traffic. This is because when you communicate via TCP, you are using a 3way handshake. TCP based protocols require an ACKnowledgement of the data received. So you need to use some upload bandwidth to ACK the download side.

That's why we'll likely still want to cap our upload 5-10% below our max in the torrent client, to allow other users on the network to not get throttled as badly on downstream (that way there is always 10% left for ACK packets).

I've submitted my request to github. Thanks for your reply.

That case may be covered by "Apply rate limit to transport overhead" in Tools>Options>Speed (Preferences>Speed on Mac, I think).  If so, that is a much more elegant and precise way of handling the issue.  uTorrent has a similar option, although last I tried uTorrent I was able to determine that the option did not include all overhead as I would expect.  In qBittorrent I use the option without issue, but haven't done a careful study to determine if it does account for all the network overhead or not.  As expected, though, upload speeds are effected by download speeds and vice-versa.

That's why we'll likely still want to cap our upload 5-10% below our max in the torrent client, to allow other users on the network to not get throttled as badly on downstream (that way there is always 10% left for ACK packets).

You SHOULD do that regardless of download states.

The "rule of thumb" is to set your client maximum upload rate at no greater than eighty percent of your connection capability, as determined empirically (use speedtest.net) rather than taking the optimistic estimate of your ISP.