1.8.2. Torrent upload cap halves single-leech upload if set above 90

[Sepussini]

Hi,

I was troubleshooting my "1 seed to 1 peer" torrent upload speed troubles (seeded at <60 even though capable of >90), but could not get any suggestions given to work (yes, I went through what is considered mandatory reading on the forums). Then I discovered the cause was unexpected µTorrent behaviour.

I tried getting help for this in the IRC channel, but no go. Then searched the internet to see if others had noticed the described behaviour, but could not find mention of it for whatever reason - so here is a Bug Report post.

Related hardware briefly:

Intel E8400

Asus IP35 Pro (integrated NIC used)

32bit Win XP Pro SP3

D-Link DI-524 router, latest firmware, ethernet connection, configured to allow µTorrent and ICMP

Siemens Speedstream 5100 bridging ADSL modem, not configurable (8/1 connection, no throttling, shaping)

µTorrent settings briefly:

Global UL 90k

Global DL 720k

Encryption Enabled, Legacy incoming allowed

Global connections 200, Torrent connections 60

Torrent upload slots 3, additional slots disabled

Most other settings are left at defaults, no reason to change

To reproduce:

1) Start µTorrent - only mIRC, F-Secure Client Security (enterprise AV+FW) running

2) Create new torrent - private, no trackers, piece size 2M

3) Start forced torrent seeding, give .torrent to friend, have them start it and add seed manually

4) Set torrent-specific upload cap to over 90 (with or without altering global cap)

Result >> Seeding speed was 80+ to a single leech with the torrent's cap at 90, but bounces between 70-80 with cap at 91, then plummets to 50-60 with anything over 91

That's about it. Setting cap back to 90 boosts speed instantly back to 80+. Multiple leechers can get 100 upload from my seeding, same as FTP uploading, but that starts to hurt my download.

I'm guessing this is by design somehow, but I can't see the logic behind it since I don't know how the cap works.

[jewelisheaven]

It doesn't sound like it's by design... only that the case whereby your torrent caps are over the global caps means uT doesn't override it and enforce the hard cap.

You notice upload fluctuate actually for up to 2 minutes after resetting either the global or per torrent limits, even moreso if you get many [uTP] connections.

Additional questions: for verification, when you set your ONLY RUNNING torrent to the SAME limit as the global cap you didn't maintain the set limit correct? And when you had no per-torrent limit the ONLY RUNNING torrent was able to maintain the hard cap?

Can I ask why you're enforcing upload caps at all if you're a single-seeder?

[Sepussini]

I should have mentioned that I set the Global Cap equal to or over the Torrent Cap when I experimented. Even tried 200 Global with 90, 91, 92, 100 and 200 Torrent, same effect.

I've only noticed this with individual leeches when I'm sharing in this 1-to-1 manner. There is no fluctuation what-so-ever, at least according to µTorrent's displayed values. Speed jumps to 80+ instantly when cap is set right, plummets to sailing between 50-60 if set wrong. I sat on the computer the whole time to see if the jumps were temporary, but the speeds instantly went to their given range (+/- 5 kB/s variation) and kept themselves there.

Regarding additional questions, yes, the only running torrent obeyed the cap I set in µTorrent itself (what I refer to as Global) and if the Global Cap was 90, everything was okay, but anything above and the problem occurred. This I didn't test as extensively as the torrent-specific cap though.

I have the caps on because I've found my optimal values. 90 kB/s is about as fast as my 1Mbit upload will go steadily. If it goes over that, downloading suffers and the upload speed becomes unstable (better to have ~90 constant than 70-100 fluctuation). Anything at or below 90 keeps sailing pretty steadily even if I download from FTP or surf video sites like Youtube. In other words, my cap is set to be as fast as my connection allows, so it's not for restriction purposes, but for stability.