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Optimizing TCP/IP for Windows On this page you might find some usefull information I discovered when I was optimizing my dialup connection, figuring that with an ISDN upstream and Satellite downstream, it should be possible to get a fairly good connection. This info can be usefull for other types of connections as well, like ADSL and GPRS! Some of the information I got from the EuropeOnline helpdesk people and some form JHPS Networking.

Dialup Indicator ?

source: Europe Online Helpdesk

First some information about the modem-indicator you can find in the systray (lower right corner of your Windows screen). What does it mean/indicate ?

In the windows SysTray (in the lower right corner of your Windows 9x/NT screen) indicates transmittion (Tx) and receipt (Rx) of data.

The newer versions of Windows (2000 and XP for example) have a similar icon in the systray which is used for normal Ethernet and Wireless Lan connections as well:

This can be usefull if you're receiving data from a different source (ie. Internet by Satellite).

Recommended Registry Settings for Windows 95

source: JHPS Networking

Optimize packetsize:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Class\NetTrans\000n

(Where "000n" is your TCP/IP protocol. It contains "TCP/IP" assigned to the "DriverDesc" Value)

Key : MaxMTU
Value : 1500 (Highest)

You can define your own highest MaxMTU by pinging your ISP server using:

Ping -f -l 1500 www.myisp.com

If you get "Packet needs to be fragmented but DF set." lower the size to 1472, if you get a reply, use a value of "1500" for MaxMTU. If not, lower the size until you get a reply, use the highest value at wich you still get a reply

Recommended Registry settings for Windows 98

source: JHPS Networking

Windows 98 has some improvements in the TCP/IP, including Large Window support, support for Selective Acknowledgments and support for Fast Retransmission and Fast Recovery. The Registry setting you should implement are listed below.

Optimize packetsize:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Class\NetTrans\000n

(Where "000n" is your TCP/IP protocol. It contains "TCP/IP" assigned to the "DriverDesc" Value)

Key : MaxMTU
Value : 1500 (Highest)

You can define your own highest MaxMTU by pinging your ISP server useing :

Ping -f -l 1500 www.myisp.com

If you get "Packet needs to be fragmented but DF set." lower the size to 1472, if you get a reply, use a value of "1500" for MaxMTU. If not, lower the size until you get a reply, use the highest value at wich you still get a reply

Optimize Recievewindow:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\VxD\MSTCP

Key : DefaultRcvWindow
Value : 372300
Data Type : REG_DWORD
Decimal var, or string var, has to be a multiple of MSS for best results, i.e. (MaxMTU-40) x number.
The maximum value of this setting is 2*30, or 1Gb in Windows 98.
Recommended settings to try are 372300, 186880, 93440, 64240, 32120 and 8760 (in that order).

Key : DefaultTTL
Value : 128
String var, 32, 64 or 128

Key : PMTUDiscovery
Value : 0
Data Type : DWORD
Decimal var, zero for optimal performance

Key : PMTUBlackHoleDetect
Value : 0
Data Type : DWORD
Decimal var, zero for optimal performance Windows

Timestamps:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\VXD\MSTCP\Parameters

Key : Tcp1323Opts
Value : 3
Recommended setting is 3.

Key : SackOpts
Value : 1
Recommended setting is 1.

Key : MaxDupAcks
Value : 3
Data Type : DWORD
Decimal var, taking integer values from 2 to N.
Recommended setting is 3