Large TcpWindowSize

[Eugene Firsov]

Hi.

I am trying to make a very large TCP receive window size in Windows XP SP2.
According to Microsoft I should set following registry parameters:

Tcp1323Opts = 1 or 3
in HKLM\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
to turn on TCP window scaling, and

TcpWindowSize = 0xffffff (1048575) (for example)
in
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\{adapter
ID}

OK, for the experiment, I set up this parameters on two computers connected
via LAN and make a test TCP connection between them. But Network Monitor
shows that window size in SYN packets is still equal to 65535 and scale
factor is 0.

3 2.241148 {TCP:94382, IPv4:94381} 192.168.0.2 192.168.0.1 TCP TCP:
Flags=.S......, SrcPort=1057, DstPort=3125, Len=0, Seq=1063837360, Ack=0,
Win=65535 (scale factor 0) = 65535
- TCPOptions:
- WindowsScaleFactor:
...
ShiftCount: 0 (0x0)

What am I doing wrong? May be there are other factors that affects TCP
window?

 

[Jack \(MVP-Networking\).]

Hi
May be this can Help.
Optimizing the TCP/IP Stack - http://www.ezlan.net/Internet_Speed.html
Same utility can be used for other type of experimentation with the TCP/IP
parameters.
Jack (MVP-Networking).

 

[Eugene Firsov]

Thanks Jack. I've already found the solution. I should add
GlobalMaxTcpWindowSize parameter in
HKLM\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters