:: Appendix A - Details of speed tweaking

Following are the steps to manually tweak; we are taking the example of Windows 98.

First step is to backup your registry. From the Start menu, choose Run and enter regedit. The Registry Editor will appear. Pull down the Registry menu and select Export Registry File.

Name your file and save it on an external floppy disk. The Registry Editor also keeps its own backup, which you can load by typing scanreg/restore from a command line. This backup is overwritten after five editing sessions though, so don't rely on it.

Now you are ready to mess with your registry. If anything goes wrong, follow the above steps, but choose Import Registry File and load the original registry settings from your floppy.

These tips involve the creation of new key values in the registry. Use the window on the left like Windows Explorer until you get to the folder you want. Each folder is a key and contains a number of values. Create a value using the Edit menu if necessary. Click on the value you want to modify and then go to the Edit menu or right-click to modify the settings.

There are three values we want to create or change. They are:

MTU: This stands for Maximum Transmission Unit. It is the largest packet size your computer can send without breaking it up into smaller packets. Bigger is better.

MSS: This stands for Maximum Segment Size and is the largest packet your computer can receive from the network. In a conversation between two computers the smaller MSS value is used to determine packet size. This is related to MTU and is usually 40 less than the MTU (40 is the packet header size).

RWIN: This is the TCP Receive Window. It's related to MSS and determines how many packets the transmitting computer can send before it needs an acknowledgement. Setting this high lets you send more packets without waiting, but also requires you to send more packets if an error occurs. RWIN is a multiple of MMS, usually three or four times.

Winsock: Not a variable, but the Window's Socket Library. This is the technical specification that handles communication between a TCP/IP application (like a browser) and your computer's TCP/IP protocol stack that interfaces with other computers.

Let's start with the MTU.

Go to the Start menu and select Run. Type regedit. Open the keys (the folders) as if you were using Windows Explorer. Go to: HKEY_LOCAL_MACHINE --> System --> Current Controller Set --> Services --> Class --> NetTrans.

There should be a number of keys starting with 000. Click on them looking for a key containing the value name DriverDesc and the value data is TCP/IP.

You will be adding a new value to this key.

1. Make sure you have the correct key selected
2. Using the Edit pull-down, select Edit -> New String Value
3. New Value #1 will appear in the key.
4. It should be highlighted for you to name it. Otherwise, select Edit -> Rename. Make the name of this value "MaxMTU."
5. Double-click MaxMTU and type 1500 in the value data box

If you are a DSL user and your ISP uses PPPoE (Point-to-Point protocol over Ethernet), you should set your MaxMTU value to 1492 or less.

The next steps may require you to experiment with your settings to get the best values.

Start by opening the following keys: HKEY_LOCAL_MACHINE --> System --> CurrentControlSet --> Services --> VxD --> MSTCP

As in the previous step, you will provide the value names and values for the MSTCP key. Please take special care to use the correct variable type when defining a new value pair. These are the values you will be defining:

DefaultRcvWindow="64240" Type: String Value

Try the setting in this order: 64240, 46720, 32120, 17520, 11680. This string value should be a multiple of MSS and has a maximum of 1Gigabit in Windows 98.

PMTUDiscovery="1" Type: String Value

This value is a Boolean or true/false option. True (1) lets your system establish connections at an optimal speed with other systems. False (0) will send fixed sized packets as defined in MaxMTU. You want to set this to "1" so your computer will go as fast as possible.

PMTUBlackHoleDetect="0" Type: String Value

True (1) tells the computer to locate "black hole routers." This can slow down your connection. Leave it off by setting this value to False (0).

TCP1323Opts="3" Type: DWORD Decimal Variable

This value refers to windowscaling and timestamp options. It's used when sending data to a computer with a buffer greater than 64k. A setting of 3 enables both, a value of 1 turns off timestamping, and a value of 0 turns off both settings. Set it at "3" and make sure you click on Decimal value and NOT Hexidecimal.

SACKOpts="1"Type: String Value

This value is another boolean and controls how your computer resends the same information if packets are lost. True (1) turns Selective Acknowledgements (SACK) on. False (0) turns off SACK. Turn SACK on by setting this to "1".

The next key we need to adjust is: HKEY_LOCAL_MACHINE --> System --> CurrentControlSet --> Services --> VxD --> MSTCP --> Parameters

This key requires one more value:

MaxDupAcks="3" Type: DWORD Decimal Variable

This value controls how quickly your computer sends new data if packets are lost. It can be set as "2" or more. Set it at "3" and make sure you click on Decimal value and NOT Hexidecimal.

Go back and check your work for spelling and proper types. Then reboot and test your speed using any of the available speed tools.