With this particular torrent I'm connected to only 6 of 83 leechers and 11 of 75 peers, even though my limit is set to 100.

Perhaps this accounts for some of the perceived slowness of KTorrent?

I'm seeing a lot of this in my log plugin:
"Authentication to 69.123.113.142 : failure"

I didn't think P2P connections were even authenticated. Are they?

I think so, but AFAIK the authentication in KTorrent stands for the level of firewalled.

Authentication(S) to 000.00.00.000 : ok means that NAT is working optimal
Authentication to 000.00.00.000 : ok means that one of you is firewalled
Authentication to 000.00.00.000 : failure means that there was no possibility to make a connection because both of you are firewalled

So that can explain a lot of the connections you weren't able to establish.

If that's the case, then I guess it must be all the other peers' faults as I know I'm not firewalled. :-/

In theory that's impossible because both sides must be firewalled for not being able to establish a connection between two peers.

But, i must say that i also see some authentication failures once in a while, i assume this is caused by the IPfilter plugin but i'am not sure for myself. Maybe George or Ivan have something to share about this.

Authentication failures can have all sorts of reasons, the handshake can be wrong, the info_hash is for another torrent, the peer you are trying to connect to isn't online anymore or isn't sharing the torrent ...

With this particular torrent I'm connected to only 6 of 83 leechers and 11 of 75 peers, even though my limit is set to 100.

Most trackers do not send back the whole peer list, you can do a couple of manual announces to get more peers quickly. And just because the tracker says that there are X seeder and Y leachers, that doesn't mean that they are actually online.

Btw, if you are still using a version prior to 1.2, please upgrade.

If the interval which you contact the tracker is 1 hour, and one minute after you contact it, a peer decides to call it a day, you will not know if that peer is offline (if you even know of it's existence).

I'm seeing a lot of this in my log plugin:
"Authentication to 69.123.113.142 : failure"

I didn't think P2P connections were even authenticated. Are they?

Authentication is just a big word for sending back the correct handshake.

Authentication failures can have all sorts of reasons, the handshake can be wrong, the info_hash is for another torrent, the peer you are trying to connect to isn't online anymore or isn't sharing the torrent ...

With this particular torrent I'm connected to only 6 of 83 leechers and 11 of 75 peers, even though my limit is set to 100.

Most trackers do not send back the whole peer list, you can do a couple of manual announces to get more peers quickly. And just because the tracker says that there are X seeder and Y leachers, that doesn't mean that they are actually online.

If the interval which you contact the tracker is 1 hour, and one minute after you contact it, a peer decides to call it a day, you will not know if that peer is offline (if you even know of it's existence).

I'm seeing a lot of this in my log plugin:
"Authentication to 69.123.113.142 : failure"

I didn't think P2P connections were even authenticated. Are they?

Authentication is just a big word for sending back the correct handshake.

Btw, if you are still using a version prior to 1.2, please upgrade.