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Message: <blockquote data-quote="||~DxxCxxxx~||" data-source="post: 3488029" data-attributes="member: 137393">Changing your MTU Size for Optimal Internet AccessChange the Maximum Transmission Unit (MTU) Size (Windows NT/2000/XP) Popular<img src="http://dedicated.sbcis.sbc.com/NDWS/img/sla/Fig1_DIASLA_boundaries%5B.gif" alt="" class="fr-fic fr-dii fr-draggable " style="" />This parameter specifies the Maximum Transmission Unit (MTU) for a network interface. By optimizing the MTU setting you can gain substantial network performance increases, especially when using dial-up modem connections.MTU stands for Maximum Transmission Unit and in basic terms, it defines the maximum size of a packet that can be transferred in one frame over a network.Open your registry and find the key below.[HKEY_LOCAL_MACHINE\System\CurrentControlSet\Servic  es\Tcpip\Parameters\Interfaces\[Adapter ID]] ( You will have a few of these in there is you have got multiple adapters)Create a new DWORD value, or modify the existing value, called "MTU" and set it to equal the required MTU size in decimal.Recommended Values# 576 - Dial-up Connections# 1492 - PPPoE Broadband Connections# 1458-1500 - Ethernet, DSL and Cable Broadband Connections ( recommend 1458 or 1480)Restart Windows for the change to take effect.Note: For Windows NT 4 the key is [HKEY_LOCAL_MACHINE\System\CurrentControlSet\Servic  es\ Tcpip\Parameters]Note: IP datagrams may span multiple packets. Values larger than the default for the underlying network will result in the transport using the network default MTU. Values smaller than 68 will result in the tranport using an MTU of 68.YOU ALTER THE REGISTRY AT YOUR OWN RISKRegistry SettingsSystem Key: [HKEY_LOCAL_MACHINE\System\CurrentControlSet\Servic  es\Tcpip\Parameters\Interfaces\[Adapter ID]]Value Name: MTUData Type: REG_DWORD (DWORD Value)Value Data: Default = 0xffffffffI would recommend using a program called <a href="http://www.dslreports.com/front/DRTCP021.zip" target="_blank">DrTCP</a>**************************************************  **********************How to Use DrTCP Q: DRTCP: How do I use it, & what are all these settings? A: DRTCP works with Win95/98/98se/ME/2K/XP.This is not meant to be a Tylenol inspiring, technical documentation, but merely a basic guide to understanding how you can best use this great tool (surprise at end).DRTCP is not a patch, but a shortcut (GUI interface) into your registry. It does not enter anything by itself. <img src="http://i16.tinypic.com/66bl3iq.gif" alt="" class="fr-fic fr-dii fr-draggable " style="" />TCP Receive Window: This is where you set RWIN (RcvWindow). RWIN is the single most important tweak. Raising Rwin from default (8760 for Win95/98/98SE/NT and 17520 for WinME/2K/XP), can greatly improve download speeds. Why? Here is my kindergarten analogy: Default RWIN for broadband, is like having a tiny straw in a thick milk shake, only so much can get through the straw (line), so fast. By putting a larger straw (higher RWIN) in that same thick shake, you allow more shake (data) to come through faster, to a point that is. After which, there is no more improvement, and shake (data) can start spilling all over (packet loss). So the key is, to find an RWIN that fits your line just right. This is blank before changing from default.The formula for finding your "ideal" RWIN, is to take your latency (average ping time in ms x 1.5), multiply that by your advertised (download) speed, and divide that by 8.Note: If setting RWIN below 8192, try using even multiples of MSS.Windows Scaling: 65535 is the highest RWIN you can use without Windows Scaling being turned on. So simply put, Scaling is needed to enter any number higher than 65535. However, you must also have the updated vtcp.386 patch (WinME/2K/XP does not need a patch). Relax though, most users do not need to go higher than 65535. Windows Scaling "Defaults" to off (same as No).Time Stamping: The need for this seems to be in question, at least with RWIN under 65535. If you have a line where latency varies a lot, or a "long fat pipe" (for example, pure satellite connection), then Time stamping should be beneficial, so experiment with it. Time Stamping "Defaults" to off (same as No).Selective Acks: This improves throughput (speed) on lines that tend to lose packets, by re-transmitting only packets that were lost, if any. "Defaults" to on (same as Yes) in Win98/98SE/ME/2K/XP and is N/A in Win95/NT.Path MTU Discovery: This automatically sets your MTU (maximum transmission unit) to what type of line you have (dial-up (576), broadband 1492-1500). This is the size of packets that you can receive. The highest MTU that one can have is 1500. For users with PPPoE connection software, 1492 and lower. Without PPPoE, it should default to 1500. "Defaults" to on (same as Yes) in Win98/98SE/ME/2K/XP/NT, and is N/A in Win95.Black Hole Detection: This discovers routers on the WEB that cause MTU Discovery to work sub-optimally. "Defaults" to off (same as No) in Win95/98/98SE/ME/2K/XP.Max. Duplicate ACKs: This allows for faster re-transmission of packets (information), when packet loss is encountered. "Defaults" to blank, where blank stands for 3 in Win98/98SE/ME, 2 in WinNT/2K/XP, and is N/A in Win95.TTL: Time To Live is the amount of hops (servers) that a transmission of packets will take before all packets are lost. If you were receiving packets from 20 hops away, and TTL was set to 19 or less, all packets would be lost before they reach you. Not a speed tweak. "Defaults" to blank, where blank stands for 32 in Win95, 128 in Win98/98SE/ME/2K/XP.Adapter settings: This is where you set your MTU. Use the drop-down menu to find your NIC (Ethernet card). If you do not know which adapter you should set, please ask. Do not set them all the same. (Note: If your MTU is 1500 by default, it will be blank in DRTCP. Also: Only physical NIC's supported for XP, no dial-up adapters.Note: DRTCP defaults to showing the dial-up adapter. This has nothing to do with the other settings. It does not matter which adapter is visible when setting anything except MTU. Also: Upon reboot the dialup adapter will be showing, regardless of which adapters MTU was set.ICS Settings: Internet MTU is set when Internet Connection Sharing (a ********* program) is enabled and being used on your PC. This is where 2 or more PCs share the same Internet connection, though only one can “surf” at a time. ICS MTU should match that of the PC. This is grayed out if ICS is not being used (not ready for Win2K/XP).Also: By right clicking on the logo and choosing "About", you will find information about the version of Windows you use.Great, so what should you set all of these to? Most users can leave all of them at Default (surprise!) except for RWIN, as this has been determined to be best, most of the time, thus being "Default". After making any changes, click Save, then Exit, then reboot (restart) your PC. Use the Tab button on your keyboard to move about DRTCP. If you do not reboot, the settings will not "take".DRTCP Recommended~~~~~~~~~~~~~~~~~~~~~~Uninstall: Since DRTCP is a GUI interface (never mind), it is not installed. Therefore there is no uninstall. Right click on DRTCP and choose Delete, if you wish to.To simply set your registry back to it's default settings, set everything to "Default" or blank (cleared of value), click Save, and reboot. Done.</blockquote>

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