Leatrix Latency

What It Does

Leatrix Latency Fix will reduce your World of Warcraft latency significantly by increasing the frequency of TCP acknowledgments sent to the game server.

The average reduction in latency (based on feedback from comments) is 66%. Click the Change Log tab above to see a summary of player feedback.

System Requirements

Leatrix Latency Fix is supported on these operating systems only.

• Windows XP (SP2 or higher)
• Windows Vista (SP1 or higher)
• Windows 7

Both 32-bit and 64-bit versions of Windows are supported.

How It Works

Wow uses the TCP protocol which requires that network segments sent to your computer be acknowledged in order to provide a reliable connection.

Windows bundles these acknowledgments together and sends them in pairs. While this is an efficient way of dealing with them generally, the inevitable delays caused by the bundling process increase latency considerably.

This is because when Windows queues up an acknowledgment in order to bundle it with the following one, the game server has to wait for the acknowledgment timer to expire before sending new data.

Leatrix Latency Fix removes the acknowledgment bundling process so that an acknowledgment is sent immediately for every segment that's received. This produces a significant reduction in latency as there is no longer a delay before new data is sent to your computer.

In a normal networking environment, you would prioritise network efficiency over latency and use the Windows defaults, but in Wow the opposite is true and you want the lowest latency you can possibly get.

Typical Scenario

If you could listen to a conversation between your computer and the game server, this is what you would hear.

Before Leatrix Latency Fix is installed:

• Server: "Ok computer, I just sent a data packet over to you, got it?"
• Your computer: ...
• Server: "Come on, answer me! I don't have all day!"
• Your computer: ...
• Server: "Ok, forget it, I've waited long enough, sending another one over! Got it?"
• Your computer: "Yep, got that one, also got the one you sent before, thanks."
• Server: "Well, why didn't you acknowledge the first one when I sent it? I was waiting ages!"
• Your computer: "Sorry, I'm just trying to make the network more efficient by bundling the acknowledgments together in pairs."
• Server: "Nevermind efficiency, this isn't a corporate domain you know. You do realise that the longer you take to acknowledge a packet, the more time I have to spend waiting around instead of sending more data?"
• Your computer: "Well sorry but this is how I'm setup by default."

After Leatrix Latency Fix is installed:

• Server: "Ok computer, I just sent a data packet over, got it?"
• Your computer: "Yep, send the next!"
• Server: "That was fast! Ok, here's another, got that?"
• Your computer: "Yep, send the next!"
• Server: "Wow! What an improvement! Now that's more like it! Much better than giving me the silent treatment so I am forced to wait for acknowledgement timeouts, isn't it?
• Your computer: "Yep, it's certainly keeping me on my toes, thanks!"

Frequently Asked Questions

Got a question? You may find it's already been answered below.

The TcpAckFrequency Change

• Isn't this the infamous TCP ACK fix?
  Yes, but it's packaged in a neat little script which will make the required changes for you, so you don't need to go messing about with the registry.

• Doesn't more acknowledgments mean more upload bandwidth used?
  Leatrix Latency Fix doesn't produce more acknowledgments. It produces more frequent acknowledgments.
  
  Windows, by default, sends two acknowledgments for every two segments received. Leatrix Latency Fix sends one acknowledgment for every segment received. The number of acknowledgments sent in either case is the same, it's only the frequency which is different. The only additional upload bandwidth used is for packet headers.

• Didn't Blizzard disable this already?
  This is a common misconception but the answer is no. What Blizzard did was disable nagling, way back in patch 2.3.2.
  
  Nagling bundles small packets together into larger ones for more efficient transmission. The effects are similar - bundling packets together always produces higher latency which is why it's bad for online games. Blizzard disabled nagling because of this, however, the acknowledgment queueing system used by the TCP protocol remains.
  
  For the technically minded, Blizzard made the TCPNoDelay function redundant, as Wow now includes it by default. They didn't change TcpAckFrequency. Leatrix Latency Fix changes that.

• The displayed latency is lower but in-game latency is the same isn't it?
  As previously stated, when the game server sends data to your computer, the faster that your computer acknowledges that data, the faster the next lot of data is sent.
  
  Leatrix Latency Fix makes your computer acknowledge packets immediately, so subsequent data is sent to your computer in the shortest possible time. Anyone who thinks that this doesn't produce a genuine reduction in latency has failed to understand this simple process.
  
  The in-game latency stat is accurate. However, the amount of latency reduced and how much you notice the benefits depends on your connection and what your character is doing in the game world (since some activities will produce much more traffic than others).

• Doesn't Wow use UDP for game data?
  No, Wow uses TCP port 3724 for game data and TCP port 1119 for Battle.net authentication. You can prove this to yourself by blocking all outgoing UDP traffic on your computer/router but keeping TCP ports 3724 and 1119 open, the game will still work. But if you block TCP ports 3724 and 1119 then it won't work, it doesn't matter whether UDP ports are open or not.

• Is this TCP change against the World of Warcraft terms and conditions?
  Of course not, it's a local change to your computer's network configuration, nothing more. It's completely safe to use and it's nothing to do with Blizzard at all, or any other game publisher.

Your Computer

• Will Leatrix Latency Fix damage my computer? Can I remove it?
  There's a removal script included in the download which will completely erase all traces that Leatrix Latency Fix was ever installed. This isn't one of those scripts that changes all of your network settings and you have to reinstall Windows to get things back to normal. The installation script makes a simple change. The removal script reverses that change. You have nothing to lose.

• Are there any down sides to running Leatrix Latency Fix?
  Your PC will process acknowledgments faster so it will have to work a bit harder. This may produce a small drop in framerates.
  
  Remember that Windows networks aren't designed for online games. They're designed for general desktop computing in large networks where traffic efficiency has the highest priority. In these environments, network latency isn't important at all and bundling acknowledgments together makes sense.
  
  However, Wow players are rather unique in that they'll often use a single, TCP based application (the game client) for hours at a time and they'll want to give that application priority over any other function of their PC. It's for these players that Leatrix Latency Fix is designed for.
  
  Leatrix Latency Fix should not be installed on computers where you want to put more emphasis on network efficiency. Fortunately, this doesn't apply to most Wow players and having reduced latency is of considerably more importance.

• Does Leatrix Latency Fix work with any other games?
  Leatrix Latency Fix modifies the way in which Windows handles acknowledgments to TCP segments. As such, it will affect any application that you have installed which uses the TCP protocol to transfer data. A lot of games use UDP so won't be affected but for the games that use TCP (such as World of Warcraft and Aion), you should see a significant reduction in latency.

The Leatrix Latency Fix Script File

• I use Windows Vista or Windows 7 and User Account Control prevents me from running scripts. Can I get around it?
  Leatrix Latency Fix includes bypass support for UAC. If you are stuck behind UAC, it will ask you for the credentials of an account which has Administrator rights so that it can run.
  
  Alternatively, you can run Leatrix Latency Fix from an elevated command prompt, which you can access by right-clicking Command Prompt from the start menu while holding down shift and choosing Run As Administrator.

• Can I install Leatrix Latency Fix without restarting my computer?
  Leatrix Latency Fix will request that you restart your computer after installation. If you really don't want to do this, you can choose not to and instead disable and re-enable your network card.

• Can I install Leatrix Latency Fix silently from a batch file?
  Yes, just use 'cscript <script name>' in your batch file (eg. 'cscript "c:\Install.vbs"'). Leatrix Latency Fix will detect that you're running it from cscript and output to the command window which launched it instead of a graphical window. The installation script, removal script and checker script all support batch mode, however you need to be logged into your computer with Administrator privileges.

• Can I check if Leatrix Latency Fix is installed without running it?
  Simply run the script called "Checker" which is included in the download.

• Is this spyware, a trojan or any other nasty thing?
  No. I think Wowinterface would have closed my account by now if Leatrix Latency Fix was malicious. The script code can be inspected by anyone to see how it works and exactly what it does.

• Why make a script, why not just make a registry file?
  Because the keys which are modified are unique to the computer you're using, so it's not possible to make a static registry file and expect it to work for everyone.

• Do I need Administrator rights to run Leatrix Latency Fix?
  Yes, since it modifies keys in HKEY_LOCAL_MACHINE. If you run the script from an account without Administrator rights, you will be prompted for the credentials of a user account which has them.

Help! It doesn't work!

• I installed it and can't see any change in latency. Does it not work on every machine?
  As long as your operating system meets the minimum requirements shown at the top of this page, Leatrix Latency Fix should always work. However, you may have applied a similar fix in the past, either through manual registry changes or from using alternative software. You may not be aware that you have done this. The chances are that if you applied Leatrix Latency Fix on a fresh install of Windows on your computer, it will work, and the reason why it's not working is probably because you've already run some sort of optimisation fix or registry change in the past.

• I get an error with code 80041002 (or similar). What's that?
  Leatrix Latency Fix requires a functional WMI to work and this error (or similar) suggests that the WMI repository on your computer is corrupt. You may find this site useful to help you fix that. It describes the steps necessary to rebuild a corrupt WMI repository. I advise you to have a backup in place first. Note that this is a problem with your computer, not with Leatrix Latency Fix.

• I get an error "Can't find script engine VBScript" and some more text. What's that?
  For some reason, the VBScript engine has been removed from your system. Click Start, click Run and enter "regsvr32 VBScript" (without quotes). You should receive a message that it succeeded. If so, try Leatrix Latency Fix again.

• When I double-click the script file, it opens in Notepad instead of running it. Why is that?
  For some reason, VBScript files are associated with Notepad on your computer. This is probably the result of some software you installed in the past or some registry change that you made.
  
  VBScript files should instead be associated with the VBScript engine so that they can run. This is the default behaviour in Windows.
  
  To rectify this, do the following.
  
  Right-click the script file and choose "Open With...". A window will appear listing a selection of programs that you can open VBScript files with. If "Microsoft Windows Based Script Host" (or similar) is shown in the list, choose that, then check the "Always use the selected program" button and click Ok.
  
  If "Microsoft Windows Based Script Host" (or similar) isn't shown in the list, click Browse. Navigate to your System32 folder (normally "C:\Windows\System32") and choose Wscript. Again, check the "Always use the selected program" button and click Ok.
  
  VBScript files will now open with the VBScript engine and they'll run fine.

• I ran Leatrix Latency Fix and it didn't show a confirmation window. Did it work?
  No. If Leatrix Latency Fix installs successfully, it will always show a confirmation window and ask you to restart your computer. If you don't see the confirmation window, then it hasn't installed successfully.
  
  The most likely reason for a confirmation window not showing is that you've encountered the User Account Control window and haven't provided the credentials of an account which has Admnistrator rights.

• I have an issue with Leatrix Latency Fix that is not mentioned above. Can you fix it?
  Reports of Leatrix Latency Fix producing an error or not working are very rare. However, if you experience an issue, I'll do my best to fix it. Please describe your issue in the comments section, giving me as much detail as possible by copying and pasting the template below. Don't just tell me that it doesn't work. The information that you give me is part of the solution.
  
  Of the few problems that have been reported with LLF, it usually turns out to be a fault with the users own computer and a fresh install of Windows on the same computer does not reproduce the problem. Please keep this in mind.

• Operating system (XP/Vista/7):
• Service pack installed:
• What error are you getting (include error codes and exact wording):
• Have you tried to run LLF while logged into your computer with an Administrator account? Did it work?
• If you're running Windows Vista or Windows 7, have you tried to run LLF from an elevated command prompt (or with UAC disabled)? Did it work?
• Have you tried to run LLF on another PC? Did it work?
• Are you running the script from a network share (UNC path)? If so, what happens if you copy the script to your C: drive and run it from there?
  

And finally...!

Stop worrying and wondering whether Leatrix Latency Fix is right for you. It makes a simple change to your computer, there's a removal script in the download which removes that change.

Install it, try it for yourself over a period of a few days. If you aren't happy, remove it. Make up your own mind. It won't break anything. Most people report a noticeable improvement in button response times, as well as smoother mob movement patterns. You'll probably be one of them. So relax and stop worrying, try it and see for yourself.

Links

Here's a few randomly selected websites with references to Leatrix Latency Fix.

• Deadmen.co.uk
• Healing Way
• Aionsource.com
• Sanctum Guild
• RelicKylias Microblog
• Wow Forum
• Live Journal
• Tankspot.com

Leatrix Addons

• For more addons by Leatrix, click here.

Change Log:

Change Log:

• 1.15 - Added support for batch mode. You can now run Leatrix Latency Fix from your own batch files. Just use 'cscript <script name.vbs>' in your batch file (eg. 'cscript c:\install.vbs'). Batch mode allows you to integrate Leatrix Latency Fix into logon scripts and automated Windows setup scripts. You must be logged into your computer with an Administrator account to use batch mode.

• 1.12 - Added a checker script which will simply inform you whether Leatrix Latency Fix is installed or not.

• 1.11 - Added support for User Account Control.

• 1.00 - First release.

Code:

 This is a summary of reported Wow latency values taken from player comments.
 The overall average reduction is around 66%.
 
 Name          Before    After     Saving   Operating System
 Ckramme       280-330   44-87     89%      Windows 7 Beta
 Epitome       300-400   30-65     87%      Windows XP SP3
 Halstrom      105-155   16-21     85%
 Silenia       96-123    16        85%      Windows Vista 64bit SP1
 Skylinee      250       40        84%      Windows Vista 64bit
 Mozzi         200-300   60-80     84%      Windows 7 Beta
 Katira        586       107       82%
 Namtar        150-250   35-40     80%      Windows XP SP3
 Des1963       150-190   32-40     79%
 Shadout       100-250   30        79%      Windows Vista 64bit SP1
 Bulbul        80-100    20        77%      Windows XP SP3
 Haylie        150-200   30-50     77%      Windows Vista SP1
 Leatrix       200       55        73%      Windows XP SP3
 Marthisdil    220       70        68%
 Kunstbanause  170       55        67%      Windows Vista 64bit
 Makronom      180-200   60-70     66%
 Breener       160-250   67        66%      Windows Vista 64bit SP1
 Aceman67      356       124       65%      Windows 7 Beta
 Chobaka       100-200   40-60     65%      Windows XP SP3
 Khuul         150-250   70        63%      Windows XP SP3
 Kristie       250       100       60%      Windows 7 Beta
 Phrozenassid  180-280   90-120    54%
 XMushroom     170       80        53%      Windows Vista SP1
 Smikules      230       115       50%      Windows 7 Beta
 Toadstool     400-500   250       44%      Windows Vista SP1
 Mooshroom     300-400   200       41%
 Bleukreuz     350-450   250       36%      Windows Vista SP1
 Servi         150-300   100-200   33%      Windows XP SP3
 Alsenfaire    500-800   400-500   29%      Windows XP SP3