Receive Window Auto-Tuning on Vista.

re: Receive Window Auto-Tuning on Vista.

jm — Sat, 21 Jan 2012 08:48:28 GMT

You do seem to have it right, but many websites and commenters mix up window scaling vs. Auto Tuning. TCP window scaling is not new with Visa. Older systems like Windows 98 support TCP window scaling. TCP window scaling is enabled for any window size greater than 64kb. On those old systems users can specify window sizes greater than 64kb, but the window size is fixed until a registry edit changes it. What Vista introduced is Auto Tuning. What that does is dynamically change the window size (the scale factor) on the fly to try and make each TCP connection as ideal as possible. There can be an issue with older routers because the dynamic window size can get enormous and cause a problem. Many websites suggest to disable Auto Tuning. I don't like that because disabling it fixes the TCP window (Rwin) to 16kb, which is not very good for broadband. I like the HighlyRestricted option instead. The window can grow, but is limited, but can get into where it's better for broadband and doesn't cause problems with older routers in my testing.

re: Receive Window Auto-Tuning on Vista.

S H — Thu, 14 Jan 2010 15:17:35 GMT

Seeing similar issues with Vista (with latest updates/S.Pack etc.) and using a Dlink DWA-547 Wireless N card to connect to a Dlink DWA-615 N-class router.

The machine ticks away quite merrily on the web/using online apps etc. and streams media down over the air to a PS3 (physically connected to the router). It can run fine for a while or start dropping out after 30 minutes or so, and the Wireless connection changes to "Local only" and the PS3 can't see the media server. Also, Was streaming BBC I-Player traffic to the PS3 which kept pausing (on a 20MBps link) until the Vista machine dropped off the network, the PS3 advised it had lost connectivity to the Media server and all of a sudden it sprang into life.

No errors at all (bar a browser re-election) in any of the event logs on the PC. disconnecting and re-connecting to the network restored service. The Event logs showed the reconnection and so did the Router. no errors though shown as to what caused the drop off.

I'll try disabling the auto-tuning to see if it makes a difference. Is there a way to set this option to disabled permanently? Also, would this option being enabled conflict with QoS settings (for media streaming/Online gaming traffic etc.) being set on the Router? Currently I have those enabled.

Thanks.

re: Receive Window Auto-Tuning on Vista.

Mark — Thu, 15 Oct 2009 01:49:03 GMT

I'm trying to RDP from a Vista x 64 machine into a Server running XP Pro 64.

Its so slow (even locally) as to be unusable. It works fine from an XP machine and I can RDP from this Vista machine into other XP machines without a problem.

I tried the fixes mentioned here but it doesn't solve the problem. Please advise.

An existing connection was forcibly closed by the remote host

The Windows Directors' Cuts — Thu, 04 Jun 2009 12:22:38 GMT

An existing connection was forcibly closed by the remote host

re: Receive Window Auto-Tuning on Vista.

R Sherwood — Tue, 17 Mar 2009 19:43:47 GMT

So, is there a QoS policy that may be applied to set the autotuninglevel on Vista? Or is this only set through netsh? And, I believe the change to be persistent when set through netsh - is this the case?

re: Receive Window Auto-Tuning on Vista.

Cecil Ward — Fri, 21 Nov 2008 22:51:43 GMT

18 months on, there are still major router manufacturers who have yet to release fixes to their firmware to resolve window scaling issues.

Microsoft could help its customers by (i) liaising with manufacturers to exert some gentle pressure, and (ii) also publicising those who do the right thing and reminding the rest of how they are missing out on the benefits of getting listed amongst the righteoud and acquiring a "logo".

Suggestion. What about a patch for vista that adds a new 'split' pair of two 'subnet-vs-global' autotuning parameters to control the behavior independently wrt subnet-local vs external ip addresses? That would allow users on a fast LAN to benefit without problems caused by routers or bad servers out on the internet.

VISTA file transfer blues..

adamsalah — Fri, 25 Jul 2008 01:26:38 GMT

So I decided to reorganize my laptop running VISTA ultimate. First things first, make room on the system...

re: Receive Window Auto-Tuning on Vista.

Mark Wall — Mon, 14 Jul 2008 14:12:43 GMT

Whats the difference between "RWND Auto-Tuning" and "Window Scaling Option"(RFC 1323)?

Does Auto-Tuning adjust the max. RWND (or the scaling factor) while the connection is already established?

How does this work technically?

Or does "Auto-Tuning" just mean that "Window Scaling Option" is used per-connection (while it is established) and not globally for all connections?

Mark

re: Receive Window Auto-Tuning on Vista.

Michael L. Croswell — Thu, 03 Jul 2008 02:27:49 GMT

Is there a netsh.dll so that this could be called programmatically (as opposed to using ShellExecute or CreateProcess)?

Also, will this be fixed in Vista? Wouldn't it make sense (!) if the OS had just set this to Restricted or Disabled by default. Or perhaps, like DirectX, there would be a way to set it without going to a command-line program?

We've done work in SP1 to lessen the impact for users with problematic network devices. We've heard general feedback about the lack of more programatic access to network settings and enjoy getting more information about specific scenarios that are intresting to our customers. I'd also like to point out one more type of control of the AutoTunning setting, Group Policy. gpedit.msc -> Computer Configuration -> Windows Settings -> Policy Based QoS -> Right Click: Advanced Qos Settings -> Inbound TCP Traffic is a set of levels that map 0 -> diabled, 1 -> highlyrestricted, 2-> restricted and 3 -> normal. This allows bulk deployment of the settings in a domain.

-- Ari

re: Receive Window Auto-Tuning on Vista.

Petter Nilsen — Mon, 30 Jun 2008 10:22:29 GMT

It's interesting that IE 7+ seems to set "autotuninglevel=restricted" programmatically on Vista, as other browser vendors have been forced to do as well. If there is a reliable way to only do this if required due to buggy routers, it would be useful to know about how.

Well the mechanism is WSAIoctl SIO_SET_COMPATIBILITY_MODE with WsaBehaviorAutoTuning option. I believe Vista SP1 introduced some general mechanisms to reduce autotuning when it sees slow connections with small window sizes for sockets that do not set that option. Even with that, it's still a reactive test, the user still has to experience the bad network behavior before the stack can attempt to adapt to it.