qBittorrent official forums

I've been having this issue where heavily seeded torrents, think Ubuntu, have a lot of people with many different clients, many of which don't negotiate uBT for one reason or another. Many of these heavy seeders seem to have buffer bloat issues which is causing them to flood me with duplicate packets. uTP is not doing this because it is already latency aware.

I have wireshark'd my WAN and looked at the most offending TCP flows for dup-packets, and every single time, the seeder has an average of 1,500ms+ 1-2 hops before them. I still have relatively low latency, tens of milliseconds, but they are flooding themselves.

Why do I care? Because up-to 50% of my download is being consumed by these dup-packets, causing me to get flooded. They're effectively DDOSing me. On average, I'm seeing about 20% of my incoming traffic dup-packets. Because my stateful firewall filters out acknowledged TCP segments, I may see something like 100Mb/s in the WAN and only 60Mb/s out the LAN. With a normal healthy seeder I will see 100Mb in and 100Mb out.

If I had a simple way for qBittorrent to not download via TCP, that should stop my issue. Most TCP congestion algorithms on a bufferbloated network are bad-actors.

don't negotiate uBT

What is uBT?

ciaobaby wrote:

don't negotiate uBT

What is uBT?

Morning post. Caffeine hadn't kicked in yet. uTP

IIRC if you set encryption mode to required under tools > options > bittorrent your client will choke non-uTP peers and they'll stop flooding you.

Seems that also hurt my ability to seed. Some people have some old clients.

To answer this old post...

NOT forwarding TCP on your router to qBT on your computer would block a LOT of the really crappy old BitTorrent clients which are likely firewalled on TCP as well while still allowing UDP incoming for uTP peers/seeds.
This would require manually forwarding UDP on the router and disabling UPnP/NAT-PMP in qBT.

You would still have some backwards compatibility to TCP-only using BT clients via your outgoing connection attempts (subject to the extremely high max connection rate of half open limit in qBT advanced settings.)