Is there a TCP limit?

The resource monitor has been showing low, constant numbers of connections even with moderate bittorrent activity (>1mpbs). Are there are built-in limits on any type of TCP connection?

A bit late but still - a good idea would be to do a online test - really helps. Here is one site that's working exactly on detecting p2p (in this case BitTorrent) throttling throughout the globe.

Glasnost: Test if your ISP is manipulating BitTorrent traffic

machinus said:

The resource monitor has been showing low, constant numbers of connections even with moderate bittorrent activity (>1mpbs). Are there are built-in limits on any type of TCP connection?

Yes, there is a dedfault maximum number of connections which I believe is 20.
You can modify it in RegEdit at the locations below. The second group allows you to enable more connections for your browser which usually speeds it up as well.

However uTorrent does not open 200 TCP ports, it shares all connections on one port. (Can't speak for other torrent clients...)

Code:

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters]
"DisableTaskOffload"=dword:00000000
"TCPNumConnectons"=dword:00000080
"DefaultTTL"=dword:00000080
 
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings]
"EnableNegotiate"=dword:00000001
"MaxConnectionsPerServer"=dword:00000010
"MaxConnectionsPer1_0Server"=dword:00000010
"DisableCachingOfSSLPages"=dword:00000001

K3VL4R said:

You do not need the tcp patch for Windows 7 like you do for XP when it comes to torrents. There is a good chance that it is your ISP. More and more are traffic shaping to throttle down on P2P bandwidth. If you want to find out for sure google something like "(your isp) throttling torrrents" or "(your isp) traffic shaping" and see if others in your area are having the same issues.

It's visibly trackable right on the uTorrent window....

Go into the Utorrent Bandwidth settings and set an upper limit on downloads and uploads just a bit less than your connection's maximum speeds, then set your speed graph to update every 30 seconds. Watching the speed graph will then show you any throttling activity...
The visual cue is that with slow torrents the speed graph will be all over the place, up and down with no noticeable pattern. When you are being throttled your speeds will drop and the graph will be nearly a straight line (because you are being mechanically limited).

Mine drops to 24kbps at 5:00 every evening and doesn't come back to full speed until 2:00am the next morning... and yes it p___es me off to no end!