Windows 7 - tcp/ip registry tweak not working

Asked By Marble on 07-Feb-08 01:45 PM

I have used these 2 registry tweaks to improve the tcp throughput ,
Tcp1323Opts & TcpWindowSize. Both of them were working for a while until

Now they dont work. Its defaulted back to 64240 for the receive window.

Changing the tcpwindows amount to any size will not work I have also tried
swaping these 2 entries from \Tcpip\Parameters registry key to the
\Interfaces\######\ registry path. None seems to work. I have also tried
resetting tcp/ip by using the netsh console and resetting tcp/ip to its
default setting ...still not functioning

Anyone know what could be causing it not to function correctly & how does
one fix this ?

any & all help would be greatly appreciated

Jack \(MVP-Networking\). replied on 07-Feb-08 03:28 PM
I do not know how you tweak it and why you are choosing this value.
If you are using WinXP please look at this page.
Optimizing the TCP/IP Stack -
Jack (MVP-Networking).
Marble replied on 07-Feb-08 07:42 PM
Hi Jack

Thanks for the link. Here's a link that will anaylze your tcp/ip online.

This web page is what I have been using to verify tcp throughput

Anyone know what would block the registry setting from being read correctly?

...looks to me some type of glitch/hiccup
Marble replied on 08-Feb-08 08:14 AM
Jack I finally found & solved the problem. After sifting through number of
microsoft solution documents. Which none of the documents had a solution for
this particular problem. I decided to use netsh again, since resetting the
tcp stack didnt work might as well try and reset the winsock...and it
worked/fixed it.

Here's what to do if you or anyone else reading this thread encounters this

You have entered these two registry values TcpWindowSize (entering a size
larger then 64240) & Tcp1323Opts (set to 1) in the registry key
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters. Then
when you verify the Tcp Receive Window by going to a website like to verify the tcp receive window value
& the value still shows as the default 64240. Even tho you have entered a
different value then the default.


1) open command prompt - start>run>cmd

2) from the command prompt enter the netsh utility by simply typing netsh

3) Type winsock this will put you at the level of netsh winsock>

4) type reset

5) reboot computer

6) This will fix the problem of the Tcp Receive window size always showing
incorrect value even tho you have entered a custom value in the registry.

7) To verify your tcp receive window size, one site to visit is
Jack \(MVP-Networking\). replied on 08-Feb-08 02:55 PM
Apparently your Registry change attempts with the TCP/IP Stack ended up
partially trashing the stack.
Nice that you found a solution.
Usually the whole process goes as follow,
Using the process above is safer since it is the software that interact with
the Registry rather then an individual using the registry Editor.
Jack (MVP-Networking).
Marble replied on 08-Feb-08 04:04 PM

What had happpened was when the Nvidia Nforce network controller refreshed
it self by disconnecting then reconnecting the lan connection. It does this
if you change specific adapter characterisitics. After it disconnected the
lan connection, the OS froze..grrr... I had to reboot, thats when i noticed
the stack was loopy by not properly sending the correcting value.

I did try the drtcp works great..easy utility to use and yes it does the
interaction with the registry by adding the entries....i checked the registry

It sure did trash the stack

Thanks Jack for the links and your quick responses.

cheers!  have a good weekend