By default, Windows 95/98’s network software is configured for communication over a LAN.

When using the internet, however, this configuration is very inefficient. To maximize the efficiency, the MTU setting must be changed.

What is the MTU setting? It sets the size of the packets transmitted/ expected through your dial-up connection.

The Internet standard is 576, but since Windows is configured for a LAN, the default setting is 1500. Changing the MTU setting to 576 can have a dramatically positive effect on performance.

This software is truly amazing. My connection speed doubled after installing TweakDUN v2.2. And for streaming video, my transfer speed went from 1.8k per sec. to 4.5k per sec.!

Pages load quickly and respond instantly as they should. Take advantage of this opportunity to get a lot more speed out of your Internet connection!

TweakDUN Utility

From The Authors

“We are proud to be able to offer you TweakDUN v2.2, this marvelous utility works on all language versions of Windows 95 and 98.

The beauty of TweakDUN (DUN = Dial Up Network) is in the ease of changing the settings and/or restoring default settings.

And it is foolproof. Many people have reported excellent results with modified MaxMTU and RWIN settings for web browsing, e-mail and newsgroups, but poor success with certain games like Quake.

Some people spend a lot of time connected to LAN, where best results are obtained with the Windows 95 default settings, but wanted to improve their data transfer rates when using a dialup connection.

Now you can do it all, easily changing your settings for one purpose or another.”

TweakDUN has the largest selection of settings that can be altered over any other MTU utility that I have seen. It is also the only one of these utilities to support all foreign languages.

TweakDUN v2.2 Features

• Works on Windows 95, NT4 and Windows 98.
• Now works for America Online users too!!
• Changes MaxMTU to optimize your Data Transfer Rates!
• Registered Version also changes RWIN, TTL, and Session Keep Alive to further Tweak your Connections!
• Default values actually DELETES the changes from the registry and sets Windows 95/98/NT4 back to DEFAULTS!
• Works with ALL language versions of Windows 95/98/NT4!
• Supports Command line parameters.
• “Find MaxMTU” can sometimes help to determine the MTU of your ISP.
• Create and edit a windows hosts file to dramatically increase your web browsing speed! Import bookmarks too!

How TweakDUN Works

TweakDUN was written to help change settings in the Windows registry that affect TCP Packet Sizes.

To help improve performance in data transfer rates on the Internet, you must eliminate packet fragmentation.

TweakDUN will allow you to change the necessary settings to eliminate this fragmentation.

MaxMTU (Maximum Transmision Unit)

This is the default packet size that Windows 95/98/NT4 uses to negotiate with. When a connection is opened between two computers, they must agree on an MTU.

This is done by comparing MTUs and selecting the smaller of the two. If the MTU is set too large for routers that are between the computers, these routers then fragment this information into a packet size that the router can handle.

This fragmentation can double the amount of time it takes to send a single packet. Windows has a built-in MTU Discovery that will adjust for this by sending out a packet that is marked as “Not Fragmentable”.

Then the router sends back an error to the computer saying that the packet was too large, and Windows then lowers the MTU until there are no more errors.

If your ISP uses an MTU of 576, then every time you start a connection, Windows must adjust down to this value.

Even though Windows automatically adjusts the packet size, it still takes it time to negotiate an acceptable MTU.

By setting this value manually, you greatly reduce the amount of work that Windows must do to negotiate.

NOTE: Negotiation always adjusts downwards the value you have set, never upwards. Windows Default is 1500.

RWIN (TCP Recieve Window)

The TCP Receive Window size is the amount of receive data (in bytes) that can be buffered at one time on a connection.

The sending host can send only that amount of data before waiting for an acknowledgment and window update from the receiving host.

Matching the receive window to even increments of the MSS increases the percentage of full-sized TCP segments utilized during bulk data transmission.

MSS is the MaxMTU – 40 bytes for TCP and IP headers. The RWIN default is 8192 bytes rounded up to the nearest MSS increment for the connection.

If that isn’t at least 4 times the MSS, then it’s adjusted to 4 * MSS, with a maximum size of 64K. With the Windows 95 default MaxMTU of 1500, the default RWIN is rounded up to 8760 (1460 * 6).

You can greatly improve performance by setting this to a lower value such as 4 times your MSS (MTU-40).

The idea is to bring it to a value below 8192. Many people have better success with 6, 8 or even 10* MSS.

In some cases, however, manually setting RWIN may decrease performance because it takes the control away from windows, and if the MTU is negotiated to a different value, then the size of the RWIN is no longer an whole integer multiple.

For this to be effective you must make sure your MTU is set where it will not be negotiated to a lower value.

TTL (Time To Live)

TTL is a field in the IP header which indicates how long a packet should be allowed to survive before it is discarded.

TTL essentially determines the maximum number of hops permitted. Windows 95 default is 32, but with the Internet growing larger all the time, it is worth changing it to the larger setting of 64.

Session Keep Alive

Specifies how often to send session keepalive packets on active sessions. This will keep connections that have stalled from timing out.

The minimum is 1 minute. The default is 60 minutes. The recommended setting is 10 minutes.

Local Domain Name Lookup (Hosts File)

A hosts file is a local file used by Windows to retrieve an IP address for a domain name. This file takes priority over your specified DNS servers.

Since it is stored locally, it is an instant lookup for a Domain Name’s IP address. If you place all of the sites that you visit regularly in the hosts file, such as your mail server, etc. it will dramatically increase your internet speeds.

This prevents your computer from having to retrieve the IP address from your DNS server and saves you time.

The downside of using a hosts file, is that when an IP address changes on a domain name for some reason, the old IP address is still in the hosts file, and you will be unable to connect to that server.

TweakDUN solves this problem by giving you the Update IP option, and the Update All option for registered users.

Also in TweakDUN 2.2, you can Export and Import hosts files in the form of .twk files. You can then backup your hosts file, or trade hosts files with a friend.

Included in TweakDUN, is a sample.twk file that gives you examples of a few good domain names for your hosts file.

TweakDUN 2.2 now permits automatic importing of Netscape Bookmarks or Internet Explorer Favorites directly into the hosts file and will look up all the IP address for each entry automatically.

Please note that if you have a large folder of bookmarks or favorites, this can take quite a while (For my 1,800 bookmarks, it took about 15 minutes).

It will also take quite a while when you go to update them which should be done regularly.

Therefore, you may not want to include all your bookmarks in your hosts file, but only the most commonly visited ones.

You may wish to backup your full folder of bookmarks/favorites and then create a special edited one with just your commonly visited sites that you want in the hosts file before using the import feature.

Still not convinced? Well, read these compelling comments from TweakDUN users and Internet related technology professionals!

Overall, TweakDUN makes for a must-have client if you are the least bit interested in improving the speed of your ‘net connection… any and all modem users should definitely take advantage of the Internet optimization features offered by TweakDUN.
Forrest Stroud   Stroud’s CWS Apps

This is the easiest program I’ve seen for setting your MaxMTU.
Bob Cerelli’s Windows 95 Page

Do you have a dial-up connection to the Internet? Then stop reading and GO HERE NOW. I’m not kidding, gang. This will be the single most important thing you can do to speed up your already existing connection! Doubt it? Then try it.
Frank Vadala Virtual Sites Guide

Comparable to my DirectPC satellite connection. Test file D/L time cut from 15 minutes to 5! Web graphics are borderline instantaneous! Most valuable file that I have ever come across in 12 years experience.
E T Cochran <[email protected]>

w/OSR2.1 – easy to setup… Almost a 2X speedup, incredible!
Steven J. Ackerman <[email protected]>

Boost.. boost.. now my modem screaming at 5K/sec and sometimes even higher!! You guys are the coolest… our PC maniacs rate *****    [Indonesia]
Rendra <[email protected]>

The results are fantastic!!! It’s just amazing how much faster the connections are. Everyone should know about and have this amazing product.
Don Murphy <[email protected]>

I think my account is 2 to 4 times faster then it was before updating!!! [Netherlands]
Eric Oukes <[email protected]>

At first I just tried the MaxMtu settings for a few weeks and didn’t notice much of an improvement. I recently tried the RWIN, and ISDN changes and noticed a very significant speed improvement.
Douglas Roberts <[email protected]>

Thanks to your wonderful Supra Tip, I can achieve 46000 bps without fail!!!
Of course, at the same time I also have TweakDUN installed [Singapore]
Henrie Tang <[email protected]>

Outstanding. Nearly doubled my speed with MaxMTU alone – when I got the RWIN settings added, it got even faster. I have told every person I know with a computer about this page and ALL have achieved similar results. Thank you.
David Anderson <[email protected]>

Easy to set up. Results were utterly *stunning*!!! This is the single most useful tweak I’ve ever been given about any O/S ever!! Thanks *very* much. [UK]
Caroline Picking <[email protected]>

Can This Be Done Without Software?

Yes, if you are comfortable with using regedit.exe and modifying your registry settings, you can change the MTU setting yourself.

Tweakdun will do it for you, but understandably, many tweakers will want to delve right in and to it themselves. There are many sites that explain the process, Regedit.com is one of them.

Registration and Download

Registration is only $15 USD.

The vendor, Virtual Software, even offers a 100% money back guarantee if you aren’t satisfied with the results.

System Requirements:

• Microsoft Windows 95, 95b (OSR2), NT 4.0 or Windows 98.
• Microsoft VB5 Service Pack 3 Runtime Files (1.24MB) – Windows 95/NT4 only
  NOTE: These files are required for TweakDUN to run, but may already be installed on your system. If you are unsure then download and install these files first! Installing this latest version of the VB5 Runtime Files minimizes the potential for problems. Installing this service Pack is not necessary if you are running Windows 98.

Registration also entitles you to free future upgrades of version 2.x which may include other system tweaks for even more speed and efficiency with your dialup connection.

It also entitles you to limited free e-mail support if you have a question. Please note that your registration fee does not guarantee that these settings will improve your data transfer rates.

There are too many variables to guarantee it will work for everyone, but our survey response clearly indicates that the percentages are definitely in your favor.