Windows 2000 Options

I wondered if it were possible to change the Nagle setting in Windows 2000, and the Windows 2000 registry key HKLM\SOFTWARE\Microsoft\MSMQ\Parameters\TCPNoDelay looks as though it does the same thing as tcp_naglim_def. Note, however, that this is not in the same portion of the registry as the rest of the TCP parameters. This key is specific to the Microsoft Message Queuing software. So, although adding this key (it is not there by default) with a value of 1 will turn Nagle off for Microsoft Message Queuing, it will not affect anything else. Thus, there is nothing that a Windows 2000 systems administrator can do about an application that does not turn Nagle off.

To control the ACK timer on Windows 2000 systems, use the registry variable HKLM\SYSTEM\CurrentControlSet\Services\ Tcpip\Parameters\Interfaces\<interface-name>TcpDelAckTicks. This setting stores the value in 100-ms increments (the default is 2 or 200 ms). The value also must be an integer between 0 and 6. This value is normally not in the registry so to change the value the key must be added. Also note that because the interface name is in the path, each interface can have a different value. I'm not sure how well this actually works. Even after adding this key and rebooting, a sample trace still showed that delayed ACKs were sent every 200 ms regardless of the value that I set.