After installing Windows 7 I noticed a slight increase in network latency in several online games. It wasn’t a big deal – I’m talking 200-300ms, but this is on a connection that was reliably < 100ms in the past. Beyond the obvious settings in Windows or on your router, here’s a list of tweaks that may help quite a bit. It involves disabling Nagle’s algorithm, also commonly known as TCP no delay, which is basically an optimization of network traffic that tries to reduce overall packet volume but can cause extra latency in the connection. This should work on Windows 7 or Vista, though the same principle can probably applied to other operating systems as well.

1. From a command prompt (usually in All Programs -> Accessories -> Command Prompt) run “regedit”
2. Browse to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\Tcpip\Parameters\Interfaces
3. Browse the items under interfaces until you find one that has an IPAddress entry matching the network interface you want to affect (typically LAN IP addresses start with 192.168 or 10.0); note that if your IP address is automatically assigned by a DHCP server you may need to look for a matching DhcpIPAddress instead of IPAddress
4. Right-click on the interface and select New > DWORD (32-bit) Value, name it “TcpAckFrequency”
5. Right-click the new TcpAckFrequency value and select Modify, enter “1″ (Hexadecimal radio button should be selected)
6. Right-click on the interface and select New > DWORD (32-bit) Value, name it “TCPNoDelay” (note that TCP is all uppercase this time – that’s intentional)
7. Right-click the new TCPNoDelay value and select Modify, enter “1″ (Hexadecimal radio button should be selected)
8. Verify that both TcpAckFrequency and TCPNoDelay now show up in the adapter’s property list with types REG_DWORD and values 0×00000001
9. Exit regedit and reboot (reboot is necessary for the changes to take effect!)
10. Play a game and enjoy your new low ping

This decreased my ping in most games from 200-300ms to 50-60ms, which matches the latency I would see via a tracert to the game’s server.