Saturday, August 25, 2012

How to remove the 10 concurrent TCP connection limit in Windows XP SP2?

Windws XP SP2 introduces a few new twists to TCP/IP in order to babysit users and "reduce the threat" of worms spreading fast without control. In one such attempt, the devs seem to have limited the number of possible TCP connection attempts per second to 10 (from unlimited in SP1). This argumentative feature can possibly affect server and P2P programs that need to open many outbound connections at the same time.

In other words, even though it is not going to stop worm spreading, it's going to delay it a few seconds, limit possible network congestion a bit, and limit the use of your PC to 10 connection attempts per second in the process ! I have no problem with the new default setting limiting outbound connection attempts. Still, users should have the option to easily disable or change this setting. I might be going out on a limb here, but ever since the introduction of Windows XP I can't help thinking that I dislike all the bult-in Windows "wizardry" in a sense that the system also limits user access. That irritating trend to ease the mental load on end users is somewhat insulting, considering that Windows is to make the more "intelligent" choice instead of the end user, as well as limit their access to tuning such settings...
End of rant.

With the new implementation, if a P2P or some other network program attempts to connect to 100 sites at once, it would only be able to connect to 10 per second, so it would take it 10 seconds to reach all 100. In addition, even though the setting was registry editable in XP SP1, it is now only possible to edit by changing it directly in the system file tcpip.sys. To make matters worse, that file is in use, so you also need to be in Safe mode in order to edit it.

Unfortunately there exists no REG-key which could easily be set (would be so nice and easy, right? *smile*). The file TCPIP.SYS in the directory C:\WINDOWS\SYSTEM32\DRIVERS and C:\WINDOWS\SERVICEPACKFILES\I386 has to be changed (system dependend eventually in C:\WINDOWS\SYSTEM32\DLLCACHE, too).

Needed things:
- Windows XP SP2 (from RC2 upwards) or Windows 2003 Server SP1 beta 
- The Patcher 
- a small amount of time

Download the EventID 4226 Patcher Version 2.23d (english) from here.

Instructions:
1. Just download the patcher and execute it. It will automatically find the windows directory and ask, if it should increase/decrease. By default the concurrent connection limit will be lifted to 50.
2. For higher values, please check the help with parameter /?.

3. After a successful patch, the new TCPIP.SYS will be automatically installed. After that, the computer should be restarted.

Regards..

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