Source - Speedguide.net
Remove the limit on TCP connection attempts
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.
Rant: The forward thinking of Microsoft developers here is that you can only infect 10 new systems per second via TCP/IP ?!?... If you also consider that each of those infected computers will infect 10 others at the same rate:
second 1: 1+10 computers
second 2: 10+10*10 computers (110 new ones)
second 3: 10+100*10 computers ( 1110 new ones)
second 4: 10+1000*10 computers (11110 new ones)
....
all the way to 10*60 + 10^60 computers in a single minute (that's a number with 60 digits, or it would far exceed Earth's population). Even if we consider that 90% of those computers are unreachable/protected, one would still reach ALL of them within a minute.
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 "wisardry" 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.
You only need to worry about the number of connection attempts per second if you have noticed a slowdown in network programs requiring a number of connections opened at once. You can check if you're hitting this limit from the Event Viewer, under System - look for TCP/IP Warnings saying: "TCP/IP has reached the security limit imposed on the number of concurrent TCP connect attempts". Keep in mind this is a cap only on incomplete outbound connect attempts per second, not total connections. Still, running servers and P2P programs can definitely be affected by this new limitation. Use the fix as you see fit.
http://www.speedguide.net/read_articles.php?id=1497
