Auto Tuning - TCP/IP receive level

How to Enable or Disable the Receive Window Auto Tuning Level in Vista​

   Information

The TCP receive window size (RWIN) is the amount of data that a TCP receiver (your computer) allows a TCP sender (other internet or local network computer) to send before having to wait for an acknowledgement. After the connection is established, the receive window size is advertised in each TCP segment. Advertising that maximum amount of data that the sender can send is a receiver-side flow control mechanism that prevents the sender from sending data that the receiver cannot handle. A sending host can only send at a maximum the amount of data advertised by the receiver before waiting for an acknowledgment and a receive window size update. Auto Tuning adjusts the receive windows size continually based upon the changing network conditions. This usually happens if you have a network device (EX: Router, modem, etc.) that doesn’t support RFC 1323 “TCP Extensions for High Performance”.

   Note

The TCP window size field controls the flow of data and is limited to between 2 and 65,535 bytes, and cannot be expanded anymore. Thus, a scaling factor is used to get a larger TCP receive window size to achieve more efficient use of high bandwidth networks. The TCP window scale option is used to increase the maximum window size from 65,535 bytes to 1 Gigabyte. Scaling up to larger TCP congestion window sizes is a part of what is necessary for TCP Tuning.

When dealing with slow network performance in Vista, the problem may be due to the above mentioned TCP Window Scaling option, where many older routers and and packet firewalls do not properly implement TCP Window Scaling (doesn’t support RFC 1323), and rewrite the window scaling factor during a transmission, and causing sending and receiving sides to assume different TCP window sizes. The situation causes malfunction Internet connection, non-stable traffic that is very slow, or network connection that is only available intermittently.

Beside, Windows Vista enhances further TCP window scaling with auto tuning feature, where TCP stack in Vista system will auto tune and adjust the RWIN size to increase the percentage of full-sized TCP segments that are used during bulk data transmission based on the network scenario it encountered. And thus it’s no longer possible to specify a custom size for the TCP/IP Receive Window (RWIN) size with the inclusion of new auto tuning feature, unless the application it self uses SO_RCVBUF. However, Vista TCP auto tuning feature may get things wrong sometimes. Instead of optimal true receive window size, incompatible and out of range RWIN size may be used.

By default, Vista in normal auto tuning level will use RWIN size of 256 bytes with a scale factor of 8. This value is not suitable for all routers and servers which does not support TCP scale factor, and continue to communicate with 65536 bytes.

UPDATE: An Update on Windows TCP AutoTuningLevel - Windows 10 Forums

   Tip

Possible TCP/IP Auto Tuning Related Problems:

• Indefinite delay (hang) when opening the Certificate Services snap-in.
• Slow (sometimes no) group policy application.
• Trying to select a domain user in order to add that principal to a local security group (the object picker) would hang indefinitely.
• Instant Messaging is not working well. Sometimes not at all by not being able to sign in.
• Access to local file servers (EX: networked drives, etc.) are extremely slow and sometimes did not succeed at all (appears to hang).
• Internet connection problems.
• Extremely slow file transfers.
• Other strange unexplained network connecting issues.
• Wireless network connection problems
• Website browsing and downloads are extremely slow.

FIRST

How To See Current Auto Tuning Settings

1. Open a elevated command prompt.​

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2. Click on Continue in the UAC prompt.​

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3. In the command prompt, type in bold belowand press Enter. (See screenshot below)​

netsh interface tcp show global​

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4. Close the command prompt when done.​

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5. Run through the steps below to see if you have a TCP/IP Auto Tuning issue​

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STEP ONE

How to Restrict Auto Tuning

1. Open a elevated command prompt.​

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2. Click on Continue in the UAC prompt.​

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3. To Restrict Auto Tuning​

NOTE: Allows for the receive window to grow beyond the default value of 65,535 bytes, but limits such growth in some scenarios.​

A) In command prompt, type in bold below and press Enter. (See screenshot below)​

netsh interface tcp set global autotuninglevel=restricted​

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B) You will get a OK response if successful. If not, repeat step 3A.​

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C) Go to step 5.​

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4. To Highly Restrict Auto Tuning​

NOTE: Allows for the receive window to grow beyond the default value of 65,535 bytes, but doing so very conservatively. In this mode, Vista will by default use a RWIN of 16,384 bytes with a scale factor of 2.​

A) In the command prompt, type in bold below and press Enter. (See screenshot below)​

netsh interface tcp set global autotuninglevel=high​

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B) You will get a OK response if successful. If not, repeat step 4A.​

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5. Close the command prompt window and restart the computer to apply the changes.​

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6. If it fixed your problem stop here. If not, continue to Step Two below.​

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STEP TWO

How to Disable Auto Tuning

NOTE: Disables the autotunning feature in Vista completely, and sets and locks the RWIN receive window to the default value as 65536 bytes.

1. Open a elevated command prompt.​

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2. Click on Continue in the UAC prompt.​

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3. In the command prompt, type in bold belowand press Enter. (See screenshot below)​

netsh interface tcp set global autotuninglevel=disabled​

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   Note

You can also type in bold below and press enter after each command:

   Note

• netsh
• interface
• tcp
• set heuristics disabled
• set global autotuninglevel=disabled
• exit

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4. You will get a OK response. If not, repeat step 3.​

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5. Close the command prompt and restart the computer to apply the changes.​

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6. If it fixed your problem stop here. If not, you may not have a issue with Auto Tuning and will need to turn it back on. Continue to Step 3 below.​

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STEP THREE

How to Enable Auto Tuning Back to Normal Default

NOTE: This turns Auto Tuning back to the default on (Normal) setting in Vista. Allows for the receive window to grow to accommodate almost all scenarios. See NOTE at the top of the tutorial for more on this.

1. Open a elevated command prompt.​

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2. Click on Continue in the UAC prompt.​

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3. In the command prompt, type in bold below and press Enter. (See screenshot below)​

netsh interface tcp set global autotuninglevel=normal​

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   Note

You can also type in bold below and press enter after each command:

   Note

• netsh
• interface
• tcp
• set heuristics enabled
• set global autotuninglevel=normal
• exit

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4. You will get a OK response if successful. If not, repeat step 3.​

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5. Close the command prompt and restart the computer to apply the changes.​

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That's it,
Shawn

Related Tutorials

---

• How to See and Flush the Contents of the DNS Resolver Cache in Vista
• How to Fix the Windows Live Messenger Unable to Sign In Error in Vista
• How to Change or Disable the QoS Reserved Bandwidth Limit in Vista
• How to Create a Local Area Network Connection Status Shortcut in Vista
• How to Create a Network Connections Shortcut in Vista
• How to Enable or Disable the Chimney Offload State in Vista

 

[NevGeorge]

Brilliant! it worked for me:D

Nev

 

[Brink]

Your welcome NevGeorge, and welcome to Vista Forums.

Shawn

 

[hdbg62]

Had 'TCP' and 'Chimney' set to disabled for some time now. Being alerted again to the subject by new posts, I set everything back to 'normal' and it seems everything works a little smoother. Being relatively a user with moderate experience, perhaps I just got a bit overwhelmed by my new adventures with Vista HP/IE7.

 

[Tabu]

I have a problem that i noticed 2 days ago. I have a strange delay of 30-60 seconds before any page start to load. Is not my connection since my other computer is running just fine. I have Vista64 installed on the one with the problem. Any idea what this is coming from?

 

[valhalla]

i am also running 64 bit ultimate and im in the same boat as you m8 , its not my connection has when im downloading large files its constantley max my connection out , but when using internet explorer pages load up slowly then restart resizing started last week. run all the anti virus /spyware nothing shows up havnt put any new progs on or made any changes
debating weather to do a fresh install or not

 

[Brink]

Hello Tabu and Valhalla, and welcome to Vista Forums.

You may have a IE add-on that is causing the problem, maybe a added toolbar. Use Step One in this tutorial to see if running IE with no add-ons runs fine for you. If it does, then proceed to Step Two to find out which add-on is the problem and disable or remove it.

http://www.vistax64.com/tutorials/114310-internet-explorer-reset.html


You might also take a look at Resource Monitor to see what all is running while this happens and to see what is using the Network (step 7). You might also investigate any security program settings to see if they are interfering with it as it waits to approve it or not.

http://www.vistax64.com/tutorials/111020-resource-monitor.html


Hope this helps,
Shawn

 

[hdbg62]

Should have waited with my last post because the problem returned this morning; in the middle of browsing I just lost my internet connection. Did a diagnose and repair which told me to let it remove a certain configuration and then advised me that the problem was resolved and I did indeed get my connection back but then then in Problem Reports and Solutions I found this little jewel below; perhaps someone more knowledgeable can comment, especially on the "TcpWindowScaling" part:

NETWORK DIAGNOSTICS FRAMEWORK


Problem

Unable to diagnose/repair network problems.

Date 9/6/2008 02:15

Status Report Sent


Problem signature

Problem Event Name: NetworkDiagnosticsFrameworkV2

Vendor: Microsoft
OwnerHC: TcpWindowScaling
OwnerHCVersion: 1.0
SessionStatus: 5
HRESULT: 0
Repair: {60FF9E63-E0A8-46ed-BACA-A4B15F978F11}
RootCauseHC: TcpWindowScaling
RootCauseHCVersion: 1.0
RootCause: {4718EC19-C565-4213-A81C-10B23F073617}
OS Version: 6.0.6001.2.1.0.768.3
Locale ID: 1033

Extra information about the problem
Bucket ID: 32693631




I'm beginning to wonder if all my browsing problems are not related to my internet service which is dry loop DSL through ATT at 6000/781 kb/s max; speed tests average 5100/650. Have had a few issues with them in the past and at one point was told that I may need to downgrade to 3000 kb/s because I'm pretty close to the limit as far as my distance to the nearest point of connection is concerned; 6900 out of 7000 feet.

 

[Tabu]

Hello Tabu and Valhalla, and welcome to Vista Forums.

You may have a IE add-on that is causing the problem, maybe a added toolbar. Use Step One in this tutorial to see if running IE with no add-ons runs fine for you. If it does, then proceed to Step Two to find out which add-on is the problem and disable or remove it.

http://www.vistax64.com/tutorials/114310-internet-explorer-reset.html


You might also take a look at Resource Monitor to see what all is running while this happens and to see what is using the Network (step 7). You might also investigate any security program settings to see if they are interfering with it as it waits to approve it or not.

http://www.vistax64.com/tutorials/111020-resource-monitor.html


Hope this helps,
Shawn

I dont have any addons on IE or Firefox. I have the same problem on all browsers even in windows mail. Takes forever to connect to the mail server.

Anyway, i realized that i have this problem if utorrent is running. If utorrent isnt running then everything is fine. I have to mention that i had utorrent installed since the beginning, but i noticed this problem on the last few days. I dont have any clue how utorrent can generate such problem and not from the start. Must be another setting that changed and caused this. The only things that i did were the tweaks found on this forum and not all of them. Can be the services that i disabled? From that guide i choosed the safe ones. If anyone have more experience with Vista please advise. I tried to install another torrent client but bittorrent instalation stopped at 30% and didnt continue. I cant think on anything else than undo all the tweaks found here.

 

[Brink]

Tabu,

It seems that you have found the problem as being with the utorrent program. You might try uninstalling it and reinstalling it to see if something was corrupt with it.

You can undo the tweaks here if you like to, but if everything works fine when you do not have utorrent running, then that must be the problem.

You might post a separate post about utorrent and this problem in one of the forums to see what suggestions you may get about it.

Hope you can get a solution soon.

Shawn

 

[valhalla]

i think its got to do more with my internet has last night took my vist64 pc
and my trusty old xp pc downstairs and plugged the into my master socket and im getting hardly any upload speeds i.e 88kbs instead off 486kbs
ive got my isp looking into it at the mo

just one more question in step one when i go into cmd /global settings

my chimney offload state is disabled ----should this be enabled like your screenshot and how do i do it

thanx in advance

 

[Brink]

Hi Valhalla,

Yes, that should be enabled by default. This will show you how to enable it again.

http://www.vistax64.com/tutorials/72308-auto-tuning-tcp-ip-receive-level.html#post767810

Hope this helps,
Shawn

 

[mansrm81]

Thanks Shawn it really made my internet faster.

 

[Brink]

Your welcome Mansrm81.

Shawn

 

[Lightning Speed]

Thanks for the guide Brink! didn't know I could tweak that ^^

 

[VistaLava]

so if i haven't done anything except read the settings via netsh interface tcp show global, and i get highlyrestricted, what does this mean for Vista Ultimate SP1 32bit.

sorry, now i know it just means that windows will adjust my settings but in a very conservative fashion.
Oh and it seems that the Chimney Offload setting is off when the network card dosent support the diversion of load from the processor to the NIC.

 

[Brink]

Hi VistaLava,

I have updated the tutorial to include more information about what the settings mean and do. It's a bit techy, but it's about as simple of an explanation that I can make it to help explain them without to many boring details.

Hope this helps,
Shawn

 

[TorchMan]

Hi,

I just tried this improvment to my OS, but i was very surprised, because all this mentioned features was disabled by default. I've never done any changes.

But myabe this can be caused by few changes in the services ( followed from your tutorial above " Disable Unused Vista Services " )

Can be this caused due this tweaking of services?

Thanks in advice.

TorchMan™

 

[Brink]

Hi TorchMan, and welcome to Vista Forms.

I have not seen this caused by disabling Services before. I have quite a few disabled and do not have this.

This command will enable the Chimney Offload State.

netsh interface tcp set global chimney=enabled


The ECN and RFC should be disabled by default.

Hope this helps,
Shawn

 

[TorchMan]

Hi. I've talking about this problem whit my friend, and he said, this turned on feature can help, when you runnning at speedy internet connection ( our connection is ADSL type whit proclaimed 8Mb/s ) because ISP should have a appropriate hardware.

But anyway i try to compare this two settings and tell you my impressions....
____________

Okay, i've tried this and i must say, the enabled Auto-tuning and Chimney offload state fits better for me. I got better results on public speed test servers, ftp connections or only on our home LAN.

Thank you a lot Brink, cos thanks to this tutorial i've discovered this windows feature.

Whit big respect

TorchMan™

 

[Brink]

Your welcome TorchMan. I'm happy to hear that you are getting better results now.

Shawn