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!!!!!!!!!! WARNING !!!!!!!!!!
===============================
A Warning from MS:
"Microsoft has done much work in ensuring that the NT winsock is as self-tuning as possible.
Altering the registry values in NT can cause severely degraded Internet performance."
And now, on with the show :-)
CONTENTS
========
LEGAL BIT AND DISCLAIMER === NEW!!
PLATFORM SUPPORT === NEW!!
INTRODUCTION
WHAT DOES MTUSPEED DO?
EFFECT OF KEYS AND CHECKBOXES
WHAT SETTINGS SHOULD I USE?
HOW TO USE THE "PING" FEATURE === NEW!!
INSTALLATION
UNINSTALLING
VERSION HISTORY
FAREWELL & CONTACT INFO
LEGAL BIT AND DISCLAIMER === NEW!!
====================================
This software is NOT freeware and it is NOT shareware. I have called it "OptionWare" which means that you have the option to pay for it or not! If you think that the time I have spent creating it has been beneficial to you then a small donation ($5 or $10) would be very acceptable. If you don't wish (or can't afford) to send a donation then you don't have to. The software is NOT crippled and is NOT time limited. That is because I CANNOT GUARANTEE that it will work for you.
I assert my right to be identified as the author of this software. It is not acceptable behaviour to disassemble or otherwise hack the executable. MTU-Speed is provided "as is" with no claims to itÆs capabilities or stability. If you do not back up your registry prior to using this software then all I can say is "donÆt blame me!". Having said that I have never had any problems with it but it is sensible to take some precautions.
***** áPLEASE BACK UP YOUR REGISTRY BEFORE USING MTUSpeed!! *****
Details about backing up your registry may be found on Microsoft's Website (http://www.microsoft.com for US site and http://www.eu.microsoft.com for the European (London) site)
PLATFORM SUPPORT
================
This version of MTUSpeed is designed for Windows NT Version 3.50 and later (English language version only). It may work with other language versions but I have not been able to test it. If it doesnÆt work, restore your registry - you did back it up didnÆt you? (Big Grin) - and e-mail me with as much info as you can including the MTUSpeed Version number from the title bar (or from the top line in this file if the program won't run at all.
The NT Winsock/DUN combination is better automated than the Win95 version; PMTUDiscovery is automatically configured and RWIN is dynamic (8192 bytes rounded up to an even integer value of MSS). This may negate the requirement for altering TCP parameters in WindowsNT. Microsoft warn that altering the registry from the default values may severely degrade internet performance. However, many people have asked for an NT version so here it is.
INTRODUCTION
============
I wrote MTUSpeed when trying to optimise the throughput of my Internet access. I became tired of opening the registry, finding the appropriate keys, editing them and then closing the registry again. MTUSpeed was written using ideas gained from, amongst other sources, the guys at NetPro NorthWest who publish the "MaxMTU Fix for Win95" document (the document can be found at http://www.sns-access.com/%7Enetpro/maxmtu.htm) and, "Lynn Larrow's Place" in the US (http://www.webcom.com/~llarrow/) and Malcolm Reeves' "Win95 TCP/IP Tips and Tricks" (http://dspace.dial.pipex.com/mreeves/tips.htm) page in the UK. Although these are Win95 pages the underlying concepts are the same.
I strongly suggest that you read some of these documents prior to using MTUSpeed for the first time.
Automatic PMTU (Path Maximum Transmission Unit) Discovery is discussed in Article Q158474 in Microsoft's Knowledge Base (http://www.microsoft.com/kb/default.asp is the US Site and http://www.eu.microsoft.com/kb/default.asp is the European Site). RFC 1191 is the document that covers the use of PMTUDiscovery on IPv4 and is available at http://www.graphcomp.com/info/rfc/rfc1191.html. It is also available at http://hotline.pvtnet.cz/dokumentace/rfc/rfc1191.html.
WHAT DOES MTUSPEED DO?
======================
MTUSpeed is an interface between you and your computers registry. The settings you can enable are offered to help you improve the throughput of your internet connection. The settings will not improve the speed you connect at (although a small number of people may get a marginally higher connection speed). I do not guarantee an improved throughput; most people get 10% to 40% increase in throughput, some people get slightly poorer throughput and some people have had vastly improved performance.
To achieve this, MTUSpeed writes values to several keys in your registry. It writes:
The default values used by Windows are discussed in the Documents listed above.
The NDI options, available in Win95, are grayed out under WindowsNT.
EFFECT OF KEYS AND CHECKBOXES
=============================
When starting, MTUSpeed accesses the registry in read-only mode. The registry settings remain valid until you change them either manually or with MTUSpeed. They are not lost following a reboot. In MTUSpeed I refer to TcpWindowSize as RWIN so please don't get confused.
The effect of the "Basic" and "Optimise" buttons can be modified using the "Apply to all keys?" (which forces all TCP keys to have same MTU value) and the "RWIN enabled by default?" checkboxes (which forces RWIN to be enabled).
With the "Apply" checkbox checked, the MTU value is forced to be the same for all TCP keys listed in the dropdown box. If unchecked, only the displayed TCP key is affected by MTU changes.
With the RWIN box checked, RWIN is set to "Enable" if either of the buttons are pressed. If the box is unchecked, pressing the buttons sets RWIN to "Remove". This feature was implemented so that those using TCP/IP LANs could choose whether or not to set RWIN.
If you select the "Basic Settings" Button on MTUSpeed it will DISPLAY values of MTU=576, TcpWindowSize=2144 (if RWIN box checked) and removes the "Auto", "BlackHole" and "TTL" keys.
If you select the "Optimum Settings" Button on MTUSpeed it will DISPLAY values of MTU=576, TcpWindowSize=2144 (if RWIN box checked), disable the "Auto" and "BlackHole" keys and sets "TTL" to 64.
You can change MTU by pressing the "Change MTU" Button. MTUSpeed calculates MSS by subtracting 40 from your entered value of MTU. RWIN is calculated from the MSS times the Multiplier value (set by the slider) e.g., with MTU=1524, MSS will be calculated as 1484 and, if the slider is set to a value of 4, then RWIN = 1484 x 4 = 5936. MTUSpeed will write MTUáonly, RWIN only or MTU AND RWIN values to the registry (if you enable both). The default is dependant on the state of the RWIN checbox on the "MTU Settings" page. If you elect to write one value, the other is deleted from the registry. I suggest you either write both or MTU only.
If MTU is set to remove, the option to set RWIN values by clicking a button is enabled. You can manually set a value in the RWIN dialog box. Setting MTU to Enable will disable the RWIN Button.
If you don't want to apply any changes just close the program window and select YES in response to the dialog asking if you really want to quit.
MTUSpeed will NOT change the registry until the "Update Registry" Button is pressed. That is the only time MTUSpeed writes to the registry. It does not write to the registry on exit. Therefore, prior to selecting another TCP key from the dropdown list you should press "Update Registry" if you want the MTU settings for that key saved. With RWIN enabled, setting different MTU values for different keys can cause extreme confusion as to what the RWIN value should be. Use extreme caution when doing this. The RWIN value written to the registry is the one displayed.
Clicking with the right mouse button anywhere in the main window will bring up a menu.
Selecting "Remove Settings" and then pressing "Update Registry" returns the registry to the default WinNT condition.
WHAT SETTINGS SHOULD I USE?
===========================
Selecting Auto MTU Detection allows TCP to sort out an MTU for you. In Windows95 I generally use MaxMTU = 1152, RWIN=MSSx8, "Auto" Disabled, "Black Hole" Disabled, TTL = 64. I have not yet experimented with NT enough to have decided on final settings yet. I can say that my Win95 settings give poorer throughput in NT than the default NT settings.
HOW TO USE THE PING FEATURE
===========================
ATTENTION
Do NOT spend hours pinging your ISP's servers as he will get annoyed with you. It is un-necessary server load and is poor etiquette. You only need to do this once to confirm the value before proceeding.
NB You MUST have ping on your computer for this function to work.
Follow these steps to find a suitable MTU: (This will be much clearer if you see the HTML help by right clicking on the program window and selecting the "HTML Help" Option)
Firstly, ask yourself "Is my line quality good?". If you get connection speeds well below the speed of your modem then you probably have a poor line. If you connect at your full modem speed most of the time you probably have a good line.
If you have a poor line you should use a small MTU. If you have a good line you should use the largest MTU you can get away with.
Choose if you have a poor or good line.
MTU on a Poor Line
------------------
1. Select your Dial-Up adapter from the dropdown box.
2. If you are not connected to a TCP LAN check the RWIN box (if it isn't already checked).
3. Press "Optimum Settings".
4. Press "Update Registry".
5. Close MTUSpeed and reboot your computer.
6. You can try increasing your MTU using the instructions in "good line" but it very possible that line noise may cause excessive resending of packets. As these packets are larger than the optimum settings you may get reduced throughput.
MTU on a Good Line
------------------
1. Select your Dial-Up adapter from the dropdown box.
2. If you are not connected to a TCP LAN check the RWIN box (if it isn't already checked).
3. Press "Optimum Settings".
4. Find out what MTU your ISP uses.
5. Press "Change MTU" or right click and select it from the menu
6. Enter your ISP's MTU in the dialog box and click OK.
7. Press "Update Registry".
8.Close MTUSpeed and reboot your computer..
9. Connect to the internet then start MTUSpeed and select the "Utilities" tab.
10. Enter your ISP's MTU in the "MTU value to test" box
11. Type an IP address or name of a one of your ISP's servers in the "Name or IP of Host to ping" box. (Use the IP address of a news or mail server or some other such suitable box such as a web server or gateway) NB not all servers are set to respond to pings.
12. Press Test MTU to see the responses. If the terminal window disappears too quickly check the ping checkbox
13. If you are informed that the "packets need to be fragmented but the Don't Fragment bit was set" then you have set the MTU too large. Either your ISP doesn't know his own MTU or else you made a mistake entering the value. Reduce the value of the MTU under test until you get proper ping responses.
14. If your ISPs MTU is different to what you initially entered you should set the new value using the instructions you used earlier and then reboot. Otherwise, continue here...
15. Having confirmed the MTU used by your ISP, it is now time to find the MTU that will suit you best for the way you use the internet and the sites you visit most frequently.
16. Connect to the Internet and, with the MTUSpeed Utility page showing, enter the correct ISP MTU in the "Name or IP" box
17. Press the "Test MTU" button and if you get ping responses all is well. If you get the "Don't Fragment Bit Set" message the site uses a smaller MTU than your ISP which means you will have to try smaller MTU's in the "MTU value to test box". (Remember, if you don't get a response it may be that the server is set to not respond to pings - www.microsoft.com is one such site)
INSTALLATION
============
Run the executable which will allow you to extract the program and text file to any directory of your choice. By default it suggests \MTUSpeed\ but you can over-ride this. Make a shortcut to the executable anywhere you want. MTUSpeed does not require DLLÆs, registry entries or ini files in order to run. Use the shortcut to start the program having read the relevant docs first!
UNINSTALLING
============
Use the "remove settings" button to clear out your registry (if you want to). Delete the shortcut if you created one. Delete the MTUSpeed Folder. That's it !
VERSION HISTORY
===============
Version 4.04
-- The link to the FAQ on the about page was broken and has been fixed.
-- I have added code to allow for the fact that some people had trouble opening the readme files from the Program. This usually happened if the shortcut didn't have the proper (or any) startup folder information.
-- The email link now fills in the MTUSpeed Version name as the subject.
-- If the program cannot detect TCP it will NOT close. Instead, the MTU and Registry pages will be disabled so that you can access the other functionality.
Version 4.03
-- The bug introduced in 4.01, which I thought I had fixed in 4.02, hadn't been fixed. I had managed to increment the search counter by 2 instead of one on each cycle so, people who had TCP in even numbered keys were OK but if TCP was registered in an odd numbered key (i.e., NetTrans\0001) would get the "Cannot find TCP error" message. Apologies to all affected.
Version 4.02
-- Some people were having problems loading the help files (using Netscape 4.04) I've changed something slightly to see if it will help.
-- Fixed a bug introduced in 4.01 when I added the Version 3.08 algorithm.
Version 4.01
-- Several people had trouble using the new Win95 TCP detection algorithm in MTUSpeed Version 4.00 (having succesfully used Version 3.08). I have therefore included both the new algorithm and the old one in Version 4.01. MTUSpeed runs the new algorithm first and, if it doesn't detect TCP, runs the old algorithm automatically without user intervention.
Version 4.00 (Release)
-- Called the program MTUSpeed Pro as opposed to MTUSpeed. This is to differentiate between the Win95 only and Win95/WinNT versions of MTUSpeed.
-- Added Modem options originally from SpeedInit program.
-- Renamed tabbed page called "Other Tweaks" to "Utilities". This nbow comtains a "ping" algorithm as detailed on Malcolm Reeves' web site (http://dspace.dial.pipex.com/mreeves/tips.htm).
Version 4.0 Beta
-- Called the program MTUSpeed Pro as opposed to MTUSpeed. This is to differentiate between the Win95 only and Win95/WinNT versions of MTUSpeed.
-- Altered Operating System algorithm to allow MTUSpeed Pro to run under WinNT.
-- About box changed from being a dialog box to being on a tabbed page.
-- Added "hand" cursor to highlight email and web shortcuts on the "About" page.
-- Added New tabbed page called "Other Tweaks". Various Win95/WinNT tweaks will be added to this page.
Version 3.10 (First NT version; never released)
-- Changed keys from strings to stored constants in preparation for release of NT version.
-- Added ability to check for Operating System. If Win32s or WinNT detected this version of MTUSpeed will not run.
-- Fixed bug that prevented MTUAutoDiscover and MTUBlackHoledetect from being manually set to "remove".
-- Altered some dialog boxes so that all messages are shown on 1 dialog instead of having 3 dialogs pop up one after the other.
-- Added popup hint to highlight how the "About" box can be accessed (right click).
-- Added e-mail and website buttons to the "About" box.
FAREWELL
========
I hope you find this utility helpful. Please read some of the recommended documents (or RFC1191) to fully understand what you are trying to achieve. There is a link to my FAQ on the "About" page.
