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1. DRTCP

DRTCP: How do I use it and what are all these settings?

DRTCP works with Win95/98/98se/ME/2K/XP (not Vista, Win7, or Win8..or any higher).

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. You can download DRTCP here.

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 so fast can get through the straw (line). 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 there is no more improvement, 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. 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 Time Stamping 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: Selective Acks improve throughput (speed) on lines that tend to lose packets by retransmitting 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 feature 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 you can receive. The highest MTU that one can have is 1500. For users with PPPoE connection software, it's 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: Black Hole Detection 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 function allows for faster retransmission 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 (TTL) 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 and 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 NICs 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 dial-up adapter will be showing regardless of which adapter's MTU was set.

ICS Settings: Internet MTU is set when Internet Connection Sharing (a Microsoft 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 and 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 by Cisco.
~~~~~~~~~~~~~~~~~~~~~~

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 its default settings, set everything to "Default" or blank (cleared of value), click Save and reboot. Done.



Feedback received on this FAQ entry:
  • Thank you for this tool....It extremely improved my internet experience....I only wish I would have found it sooner....lol

    2012-06-20 16:34:30 (timmyh13 )

  • What is the Deal with windows 7 32\64 bit operating system tweeks? Can the system be set up, like described ,in the XP 32\64 bit version?

    2012-04-01 14:57:07

  • Win 7 is NOT mentioned. I would take this as a sign it is not supported BUT on the tweak test, Vista (which is not supported)is an option for your OS where Win7 is not even an option to designate the OS you are using. I take this as a sign therefore that ya'll haven't gotten around to taking a look at Win7 or updating.

    2011-09-05 13:34:44

  • It really works great! Thank you for this amazing tool!!!

    2011-01-16 20:35:48 (BigManJedi42 )

  • Thank you for the tool. I was able to play and see real differences. Wow. :-) Best wishes, Leonard Juska Costa Mesa, CA

    2010-01-16 13:35:19

  • Thanks-It truly works.

    2009-08-19 16:50:46

  • Excelent!! Thanks a lot !

    2009-08-07 21:59:01

  • Thank you. This tweak is amazing. I first used this 2 years ago, and have used it since on any machine I've used (XP)... Didn't work for me on VISTA (of course you already mention that). But I highly recommend this. Many thanks again. J.

    2009-06-10 03:54:13 (JaredZUSMC )

by DrTCP edited by Pinan
last modified: 2014-09-22 15:14:27


RWIN: How do I raise/lower mine?

Download DRTCP from this page to your desktop. Open it and enter desired value for TCP Receive Window (RWIN). Click Save, then Exit and Re-boot your PC so that the change will "take."

For Macs, see this: »All things Macintosh »How do I tweak in OS X?


Feedback received on this FAQ entry:
  • i dissagree with changing rwin on win7x64. Running the same speed tests to multiple servers after changing the rwin and mtu to 1472, I got about a 20% increase in download bandwidth. Using the same tests and servers on the same computer. I also noticed that my connection went from 82% receiver limited to 91%. I made sure that there is 0 latency between computer router and modem to make it a valid test, and using latest docsis 3.0 modem.

    2015-02-26 23:40:43

  • se7en x64 with auto-tune stack? RWIN = 261340, long way from 843880 min. is that low normal for auto-tune? thanks

    2015-02-22 11:26:05

  • I too have Win 7 x64, HOWEVER, i have a Killer2100, which,iirc, disables the Win Stack. Attempting to use this to modify the RWIN of the Killer... will update with results.

    2013-09-22 11:05:35 (shaggygoblin )

  • Definitely improves XP MCE & Pro when set to 65528, not 65535 or greater (default on MCE was ~17500). Packet counts drop to 1/3rd. That's on aDSL connection speeds of 6Mbps - 25Mpbs. Appears to be an effective setting. Makes YouTube 480p run like magic, while my Windows 7 64-bit machine with auto-tune struggles. Weird. lol

    2013-02-22 19:39:12

  • How is this done in Linux?

    2011-02-10 16:11:16

  • "Can I use this in Window 7 64bit?" - Unfortunately no. Windows 7, like Vista has an auto-tuning stack. The auto-tuning can be disabled but it works well and shouldn't be messed with unless you know what you're doing. DRTCP and RWIN tweaking will not work with an auto-tuning stack. Auto-tuning can be disabled but there's little reason to do so; it works well. HTH

    2010-12-31 08:27:24 (StreetSpirit )

  • can I use this in windows 7 64 bit?

    2010-06-02 01:07:20

  • I just upgraded my uverse from 3 mbs to 12...att techs laptop and 2 of my friends could hold that speed. however, neither of my dell laptops would break 5. ran drtcp and changed the rwin value to 300000 and done. holds 11.5 all day. thanks you saved me a lot of trouble.

    2010-05-21 12:46:43

  • Vista has a new auto-tuning stack. Tweaking the TCP Receive window is usually unnecessary.

    2008-09-25 23:01:36 (eggman9713 )

by DrTCP edited by tmpchaos
last modified: 2008-03-17 10:53:57

How do I restore default settings?

In DrTCP, blank every field. Save, exit and reboot.

by garp123 edited by JMGullett
last modified: 2007-02-19 13:21:57

What Operating systems are supported by DrTCP?

The Following Windows OS's are supported by the newest version of DRTCP021.zip:

Win95/Win95b/Win98/Win98SE/WinME/WinNT 4.0/Win2k/*WinXP

*Some WinXP users have have not been able to use DRTCP effectively.

*There are no plans to make DRTCP work with Vista or Windows7*


Feedback received on this FAQ entry:
  • Anyone care to comment on if Dr.TCP works with Windows XP x64 Edition?

    2009-11-01 17:18:49 (Dustyn )

by Skipdawg edited by Pinan
last modified: 2010-11-10 16:08:27

Why are some selections grayed out?

If a selection box is grayed out, it's likely that particular selection does not apply to your OS's setup (NT/some Win95). If you have questions or are unsure, ask in the Tools or Tweaks forum for further details.

Win95 has an update patch that will enable these. The patch is called "WinSock2" and is available in Tweaks "Links."

by Skipdawg edited by JMGullett
last modified: 2007-02-19 13:23:39

Satellite Connections: Adjustments won't take!

At this time, the tweak tester does not work for satellite connections. Since these systems use Network Address Translation (NAT), the IP address used by the tweak tester to find your computer's TCP settings is actually not reading your computer at all. It is reading the computer at the Network Operations Center that is providing the NAT services. This doesn't mean that the changes you made with DrTcp didn't take. It just means the tweak tester cannot detect the changes.

by PetDude edited by JMGullett
last modified: 2007-02-19 13:24:04

TTL: What should it be set to?

As TTL is merely a hop count, not a speed setting. Windows default of 128 is just fine. No further adjustment is needed.

Only in Win95 should it be raised from 32 (default).

by Pinan edited by JMGullett
last modified: 2007-02-19 13:24:38

I have duplicate adapter entries in DrTcp. What can I do?

1. Rename your current connection (Start/Settings/Control Panel/Network Connection, or Right click on My Network Places on your desktop and choose Properties) to a satisfactory NEW name (e.g. myadapter).

2. Start REGEDIT.EXE and using Edit/Find, search for the new name you entered in step #1.
(You will find something like this:
[HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Network\...])



3. Clear all keys only in the same level except the one that has the same new name you renamed in step #1.

4. Search again (F3 key) and repeat step #3 above until you reach the end of register.
(You will find something like this:
[HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\Control\Network\...])

5. Close REGEDIT.EXE.

6. Reboot your computer.

Warning: Editing your registry is risky business. Use the above procedure with caution.


Feedback received on this FAQ entry:
  • would you clear this up please?

    2011-07-13 22:39:48

  • Sir or Madam: Thank you for writing this FAQ. I am sorry, but I am a literal engineer, and I do not understand the directions as expressed in item 3. "Clear all around keys only in the same level except the one that has the same new name you renamed in pass 1. Would you please be so kind as to simplify this instruction item 3 for an old engineer? Thank you.

    2009-05-29 23:23:43 (machwave )

by jazzman916 edited by Pinan
last modified: 2009-05-30 01:29:56

How do I change back to default settings?

In windows xp, just delete the value in drtcp, save and restart.


Feedback received on this FAQ entry:
  • how about for windows vista or windows 7? same procedure?

    2009-11-20 21:41:05

by joewho edited by JMGullett
last modified: 2007-02-19 13:32:24