Disable Half-Open Tcp Connection Limit

[Lord Ba'al]

I just stumpled upon this, a simple entry in the registry that lets you disable the half-open Tcp connection limit :laugh:

It's from an KB article on MS describing how you can enable it on Vista SP2/Win2008 SP2, since it's now by default disabled there.

On Win7, it can be used to disable the half-open Tcp limit :cool:

Simply open regedit and go here:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\

There, change the value of "EnableConnectionRateLimiting" to '0' to disable it.

The MS article says you need to reboot after the change, but it seems that with Win7, you don't have to.

Source (Author of Tcp-Z)

MS KB article

[Nadja]

thanks for the tip. have to create a new DWORD value "EnableConnectionRateLimiting"

love those direct registry tweaks :)

Edited May 25, 2009 by Nadja

[Subject Delta]

That key doesn't exist in 7, I had to create it myself :/

[protocol7]

I used to patch tcpip.sys in XP but kept hearing conflicting reports about how effective this was. So now in 7 I've left it at the default limit of 10 and I've yet to get any 4226 EventIDs in Event Log. So is it really necessary to mess with the limit after all?

[ak03]

I think it is done for torrenting reasons

[Eric Veteran]

7 doesn't have the limit by default, so the key is unnecessary.

[joey_oggie]

Nice find :yes:

[protocol7]

  GreyWolfSC said:

7 doesn't have the limit by default, so the key is unnecessary.

Are you sure about this?

[Lord Ba'al]

  GreyWolfSC said:

7 doesn't have the limit by default, so the key is unnecessary.

Nonsense. Win7 (*all* builds until 7127!) have the usual limit of 10, as confirmed by Tcp-Z.

Perhaps they'll change that for Rtm, seeing as they disabled it for Vista SP2, but right now, it's still there.

[Eric Veteran]

  protocol7 said:

Are you sure about this?

No, I'm not sure. :) I assumed that it was back-ported from Windows 7 to Vista SP2. Hopefully it will be there by RTM.

[gregrocker]

Have been using the patch for over a year since I found it here: http://www.msfn.org/board/index.php?showtopic=125403.

Anyone have any issues with this patch? Seems to work fine in 64 and 32. I use the virtual patch driver.

[ozgeek]

  ak03 said:

I think it is done for torrenting reasons

Whaaaa? I have utorrent and don't have do anything as stupid as this for it to work!

[The_Decryptor Veteran]

  ak03 said:

I think it is done for torrenting reasons

It's done to stop malware spreading (well, e-mail viruses that spam e-mails)

It doesn't effect torrent speeds (any half open connections over the limit just wait for a second, normal connections don't count)

[Ausaitis]

From the author of TCP-Z

  Quote

Good news from Microsoft!

At May 6, 2009, In this article, Microsoft confirm that:

By default, the half-open TCP connections limit is disabled in Windows Server 2008 with Service Pack 2 (SP2) and in Windows Vista with Service Pack 2 (SP2).

Thank for this, my doubts about RateLimit long time ago has been solved by Microsoft's answer.

Last year, I found a case. In Vista, I can simply modify the value "TcpCreateAndConnectTcbRateLimitDepth" from 1 to 0 in the kernel memory, and then the Half-open TCP connections limit has been removed immediately!

But I am not sure whether this is a safe method. so, in tcp-z, this function never be active. TCP-Z only show this value.

After Vista 16670 and Windows 7 6956, Microsoft strangely set TcpCreateAndConnectTcbRateLimitDepth to 0 in default.

In latterly version of TCP-Z, it will show a lock icon to distinguish these difference.

Now, Microsoft answer: It's safe! and provide a simple modification method by registry.

When you add a registry entry "EnableConnectionRateLimiting", and set to 1 or 0, it will switch TcpCreateAndConnectTcbRateLimitDepth between 1/0 synchronously.

You can see the changes in the graph of TCP-Z.

After TcpCreateAndConnectTcbRateLimitDepth change to 1, Windows will calculate the create rate and do the limitation. In testing you can see the value is limited to 11.

This registry entry only works in Windows Server 2008 with SP2 / Windows Vista with SP2 / Window 7.

It is time to retire for me!

[carmatic]

  Ausaitis said:

From the author of TCP-Z

good to see that windows 7 is now so secure that they dont have to resort to restricting things anymore...

[gregrocker]

OK, so I add a 32 bit D word registry key "EnableConnectionRateLimiting" set to "0" here: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\

and I no longer need to run the TCP-Z patch?

Will I use a Qword key for my 64 bit machines?

[Lord Ba'al]

  gregrocker said:

OK, so I add a 32 bit D word registry key "EnableConnectionRateLimiting" set to "0" here: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\

and I no longer need to run the TCP-Z patch?

Yes. (You could still use it if you want the statistics, but there's no *need* to run it anymore with that reg entry)

  gregrocker said:

Will I use a Qword key for my 64 bit machines?

No, always a Dword.

[Naala]

Sorry for the bump, but I have to ask, is the reg entry

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\EnableConnectionRateLimiting and then a DWORD entry TcpCreateAndConnectTcbRateLimitDepth with a value of 0,

or is it

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters and a DWORD entry EnableConnectionRateLimiting with a value of 0?

While Im here, anyone knows anything about EventID 4226 - TCP/IP has chosen to restrict the scale factor due to a network condition. This could be related to a problem in a network device and will cause degraded throughput.

Thanks!

[Satchmo Bevins]

  Naala said:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters and a DWORD entry EnableConnectionRateLimiting with a value of 0?

Bob's yer uncle.

[Naala]

  Satchmo Bevins said:

Bob's yer uncle.

I dont know what to make of your answer but I assume that is the correct entry. So thanks, I actually entered the first one but later deleted it because I had two concurent BSODs I assumed were network related. Im gonna try this one and see how it goes.

But I dont understand where "TcpCreateAndConnectTcbRateLimitDepth" fits in all of this...

[Lord Ba'al]

  Satchmo Bevins said:

Bob's yer uncle.

I wouldn't want to have Microsoft Bob for an uncle :x

http://en.wikipedia.org/wiki/Microsoft_Bob

Bob had a "scrumptious" dog named Rover :x

Even though he was never fed properly and only lived on table scraps, he somehow survived and later plagued XP as a Search Assistant :x

  Naala said:

But I dont understand where "TcpCreateAndConnectTcbRateLimitDepth" fits in all of this...

Simply, it *doesn't* fit.

[Satchmo Bevins]

  Naala said:

I dont know what to make of your answer......

"Bob's yer uncle" - slang for "There ya go", "That's the ticket", "Good to go", and the always popular "That is the correct answer".

:cool:

  Lord Ba said:

I wouldn't want to have Microsoft Bob for an uncle :x

Bite your tongue! :D

[Naala]

OK, so Im a little bit smarter every day, today thanks to you, ha ha ha. But really, I thought you were being mean or something... you usually only learn the official version of another language.

So yeah, thanks for help!

[trieste]

  protocol7 said:

Are you sure about this?

Yes, he's sure about it, because there is no lock icon at the top right corner of the Vista orb.

http://www.mydigitallife.info/2009/06/07/h...patch-required/

[Lord Ba'al]

  spinning_quirK said:

Yes, he's sure about it, because there is no lock icon at the top right corner of the Vista orb.

http://www.mydigitallife.info/2009/06/07/h...patch-required/

Indeed. It also says so on the Tcp-Z homepage itself that there's no patch required :yes: