uTorrent generates hundreds of connections upon launch, 1000+ later

This is a problem that I've only recently noticed, meaning that it may be something wrong on my end, but perhaps you can help me either way. Lately, uTorrent has been congesting my network like never before. Naturally I explored a bit. I was shocked by what I found:

The above image was taken from my router's config page only a few seconds after launching uTorrent with ALL torrents set to "stop", DHT PEX and Peer Discovery disabled, and Resolve IPs unchecked. My current settings don't even allow the program to create more than 120 connections globally while uploading/downloading torrents so it's completely baffling that it would decide to do this when no torrents are even running. When I start my 5 torrents, the following happens:

If left alone for an hour that number will easily reach 2500. Naturally, this destroys network performance. Now of course I can simply limit the maximum number of connections in my router but I would like to solve this problem on the software side as it's clearly uTorrent doing something wonky, my fault or not.

My router is a Linksys WRT54G running the latest Tomato firmware. I'm running NOD32 antivirus and the Windows firewall. At the time of taking the above pictures, the connections section of the uTorrent status dialog looked as follows:

If any more information is necessary, just shout. Thanks!

INteresting. You might want to add your commets to my thread here:

http://forum.utorrent.com/viewtopic.php?id=78410

Your issue is not really a congestion problem, in the typical sense. It is a bug in the Tomato firmware.

Here is more detail than I expected to write when I started:

NAT devices build a table of pairs of addresses (some remote machine, and your machine) which it calls "connections" in your case. Since the NAT device is unaware of when a UDP connection is actually closed, these are not actually connections that your machine or the remote machine are necessarily still aware of. They are residual state the NAT device keeps around, in case some stray packet arrives.

Your router firmware fills up on slots in this table, and does the wrong thing when it needs to allocate more (if you are experiencing a problem as a result of this table being full). NATs are sadly often very poor in this regard. The correct behavior, if the table is full, should be to discard the oldest slot when a new slot needs to be made, but many disallow the creation of new slots until the oldest times out. This leaves your router almost useless until the firmware decides it's ok to make a new connection.

In any case, judging from "incoming conns since start", the "connections" your router is tracking are incoming connections, not something uTorrent is actively creating. So, disabling DHT, PEX, limiting the number of concurrent connections, all will not help to completely alleviate this issue. You could close your port (do not map manually, or with UPnP or NAT-PMP) to limit the number of incoming connections, and that hack might help you control this a little better. However, the fundamental problem is that your NAT device mis-manages slots for connections. I would recommend switching firmwares. I once had a WRT54G running the stock firmware, and did not have this issue.

Thanks Greg. Since I never used to notice this problem I'll try an older version of Tomato, or perhaps the latest beta version to see if they've fixed it. If this doesn't solve the problem I'll switch to DD-WRT.

What hardware version (sticker underside) router is that? That uT status dialog, how long was uT running for when you took it? Change UDP Assured to 90, that may help a little. Can you get another router screenie when connections are high and performance poor?