"Last ack" Galore

[Nidhogg]

Ever since I got my new computer and with it a legit copy of Windows XP Pro, I've had different problems with my internet connection (ADSL) which I never experienced before when I was still on a cracked SP2 version from May 2006 or something which I never updated. As I can't really figure out what exactly is wrong, I've learned to live with rebooting every 2-3 days as this is the only way to mend things, at least for a while.

However, there is one problem which only seems to appear when I use utorrent and let it run during the night. For some reason, I end up with hundreds, at times even thousands of "total connections" according to my X-NetStat Pro, and all of them are in the "Last ack" state. It's not possible to kill those connections (option is greyed out), and the only way to get rid of them is to use "Nuke connections", but that's only a temporary patch. Half a minute later, the "Last acks" already begin to pop up again.

The only thing that really seems to help then is yet another reboot. I don't mind that, but what I do mind is the fact that because of all these ghost connections, utorrent often can't connect to the tracker either, and thus doesn't update. The result is that the ratios always differ, and usually not in a positive way.

What is going on there? How can I fix this?

[DreadWingKnight]

What internet security software is installed on the system?

[Switeck]

Is net.max_halfopen set very high?

Is DHT, LPD, UPnP, NAT-PMP, or Resolve IPs enabled?

Are the torrents you're on having LOTS of incoming connections?

[Nidhogg]

I have AVG Anti-Virus Free Version 8.0.175, and Sunbelt Personal Firewall 4.

net.max_halfopen is on the default (I guess) value of 8. I've never fiddled with these values in the Advanced part.

The "UPnP port mapping" box is not checked, "NAT-PMP port" mapping box is checked, all the boxes in "BitTorrent" (DHT Network, LPD, etc) are checked except "Limit local peer bandwidth". Resolve IP is also enabled.

As I am usually using utorrent with private trackers, DHT, Local Peer Discovery and Peer Exchange are not allowed anyway, and the number of incoming connections isn't really that high. It of course depends on the torrent content, but overall there are hardly more than 50 peers at once.

In "Bandwidth", I've set the "Global maximum number of connections" to 40, "Maximum number of connected peers per torrent" to 30, and "Number of upload slots per torrent" to 2. I only have 40 kB/s upload speed, so I can't really share that much.

And yes, the Windows connection limit has also been patched to 50 connections via xp-AntiSpy.

[DreadWingKnight]

Probably sunbelt interfering with the closing of the connections then. Can you try with it temporarily uninstalled?

[Switeck]

DHT (if enabled) can be pretty noisy even if you're only running private torrents.

40 KB/sec upload max isn't all that bad. Lots of people only have 256 kilobits/sec upload bandwidth...which limits them to ~25 KB/sec max upload speed in uTorrent.

[Nidhogg]

Sorry for the late reply, but I was rather busy with work.

I'll disable DHT and see if that helps, but I've found out something else. When I only seed a torrent, it does NOT happen. No "Last Ack" status at all, only the "Established" IPs I have in my peer list. The "Last Ack" galore only seems to happen when I download, and eventually finish a torrent. Does this change anything?

[Switeck]

When a torrent finishes downloading, all seeds you're connected with are auto-disconnected from uTorrent. For whatever reason, they may be getting stuck in "last ack" mode. And new seeds may be attempting to connect to your ip as well, stacking up more "last ack" incomplete connections.

This is usually the sign of a damaged OS or bad software firewall. Regular Windows XP would normally clear out the old incomplete connections so they cannot accumulate in any great number.