Hi,

I'm experiencing an issue that I'd appreciate help resolving.
I've been running KTorrent on the hardware/OS described below for a while now and everything worked flawlessly. After a brief period of not using KTorrent its now downloading a number of files. It works and the downloads are fast, however every other application on this computer as well as the network find the net very very slow. It takes 45 seconds for the sparse Google home page to load. I have capped both the download and upload speed, just like I always do, and I have 50k download and 10k upload bandwidth to spare and that has always allowed for a very decent browsing experience.

The only thing that changed is that this time KTorrent is handling around 142 torrents (currently 52 downloads and 90 uploads). Previously, I let it handle 20 torrents at the most. Thinking that might be the problem, I searched the net for optimization tips and found a few that are not KTorrent specific and tried to adapt them. They mostly handled the parameters listed below, and they did not fix the problem.

Any Ideas?

Is there a detailed explanation of the options listed below and how their settings affects KTorrent and the connection? I think that would come in very handy.

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Software: KTorrent 2.2.5 on Kubuntu 6.10 (KDE 3.5.8) with server kernel
Hardware: 1.6 Duo Core with 1G RAM and a big RAID array.
DSL connection: 2 Mbit Down / 0.5 Mbit Up
DSL modem: Linksys WAG54G

KTorrent settings:
Maximum downloads: 0
Maximum seeds: 0
Maximum connections per torrent: 30
Global connection limit: 800
Maximum upload rate: 40
Maximum download rate: 150
Number of upload slots: 2
DHT: enabled
Encryption: enabled, unencrypted connections allowed.
DSCP for IP packets: 0
Maximum number of connection setups: 50

Try decreasing the Maximum number of connection setups to 10, some routers don't really like to many connection setups, which results in other apps not being allowed to open connections.

Thanks for the reply.

I tried decreasing the Maximum number of connection setups to 10 the last couple of days but that didn't work. Any other ideas?

Thanks.

Try disabling DHT. DHT can cause a large uncontrollable number of mappings that exaust the same router limits as above, but are not easy to control given UDP's connectionless nature.

I find that downloading torrents with any program will slow other web based apps down (internet browser, instant messanger, etc). What I did was scheduled my torrents to download from 11:30pm to 9:30am (times when I'm not using the computer. It works out pretty well, and if you need something before then, you can always force start it.

You're using a Linksys router, which, sadly, can't handle a huge amount of open ports at a time - essentially what any torrent program needs to do.

Most Linksys routers I've dealt with so far are capped at about 256-512, and they're set up so that these open ports expire after an incredibly long amount of time, so if you're trying to torrent using the default settings... good luck. Nothing short of a reset of the router will fix this, unless you're willing to try the following:

Try flashing the router with DD-WRT (or whatever brand of firmware you like that gives you access to some more settings).
Change the maximum ports to the max the router can handle (it's in the 4096 range, typically)
Change the timeouts to 60 seconds maximum (I think the default is 3600 seconds, which is unnecessarily huge)

You'll find that everything starts working smoothly again if you do this...