Optimizing TCP/IP communication on Windows 2003 Server

So all reg keys in the path HKEY_LOCAL_MACINE/SYSTEM/CurrentControlSet/Services/TCPIP/Parameters that you list above apply only to the TCP/IP stack, which largely is the same in Windows 2K3 or XP as it is in previous versions of Windows based on the NT kernel (and probably Windows 9x, for that matter).  So the changes to your Windows 2K3 server will have the same effect as they would on an NT box.  Note however that the syntax has changed from earlier versions of NT, so not all of the settings will have any effect, and in fact, some are duplications of older, deprecated commands.

Note that these modifications will affect the TCP/IP stack on this server (more specifically the TCP protocol), which means that it will affect all TCP connections to this server (including FTP, SMTP, Windows File Sharing, HTTP, etc.).

The good news is that none of these modifications is going to do anything to the OS, and you can always change them back to the default (by deleting the key) if you have problems.  So no need to worry as long as you only mess around within the Parameters path and nowhere else.  And these changes are really "tweaks," not big atomic changes to the stack, so you can tinker with some confidence here.

Basically, here is what each one does (and the default values for WinXP/2k3):
 TcpMaxDataRetransmissions (default=5): number of times a segment (piece of data) is retransmitted when no ACK is received from the peer (raising this will increase the number of retransmits, increasing traffic and a situation where packets are lost, but also increasing the amount of time the device will keep the connection open when data is lost).  After "n" attempts the connection to the peer is forcibly closed (i believe with a TCP RST)
 TcpMaxConnectRetransmissions (default=2): same as above, but for retransmits of initial TCP connection setup attempts (rather than data) -- raising this will make the device try longer to set up a connection
 TcpWindowSize (default=8760): tells the peer how many bytes of data it can send before waiting for this host to send an ACK, before sending more data -- if you raise the window, you can send a lot more data before the sender has to hear back (this speeds up data transfer on reliable/low-latency connections -- you can read more about this at http://www.dslreports.com/faq/tweaks/5._RWIN )
 
The following registry keys are ignored in current builds of Windows NT (i.e., XP, 2k3) (So if you try creating the key and setting a value for any of them, Windows 2K3 will just ignore it):
 TcpKeepCnt
 TcpKeepTries
 TcpMaxRetransmissionAttempts (replaced by TcpMaxDataRetransmissions)
 TcpMaxConnectAttempts (replaced by TcpMaxConnectRetransmissions)
 TcpSendDownMax -- cant find anything useful about this, never seen it, never used it -- typically receiving ends specify how much data can be send, not senders.  the only reference i found was in an NT 3.51 page that talked about queuing.  but in these days of big buffers with lots of memory, i suspect this is obsolete.

Now, note that the only settings that are really going to do much of anything are the TcpWindowSize and the TcpMaxDataRetransmissions.  The first will allow more data to be sent, but absence of that setting should not cause a read error.  The TcpMaxDataRetransmissions setting could account for that, but again, unlikely.  I would be surprised if any of them make any difference as to your app.  If so, whoever wrote the update to the app, did a crappy job of writing it so it can interoperate with stock Microsoft TCP/IP stack settings.

HTH

kr