Registry Guide for Windows Registry Guide for Windows
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WinGuides Network and Software
Registry tweaks, tricks & hacks to optimize, enhance and secure Microsoft Windows.

Cable Modem and DSL Speed Tweak to Increase Performance (Windows NT)
Category: Home > Network > Internet and Remote Access

Use these settings with your Cable Modem or DSL broadband Internet connection, to boost network throughput performance with Windows NT.

Open your registry and find the key below.

Create the following DWORD values, as most of these values will not already exist you will need to create them by clicking on 'Edit -> New -> DWORD Value' and then set the value as shown below.

DefaultTTL = "80" hex (or 128 decimal)
Specifies the default time to live (TTL) for TCP/IP packets. The default is 32.

EnablePMTUBHDetect = "0"
Specifies whether the stack will attempt to detect Maximum Transmission Unit (MTU) routers that do not send back ICMP fragmentation-needed messages. The default is 0.

EnablePMTUDiscovery = "1"
Specifies whether the TCP/IP stack will attempt to perform path MTU discovery as specified in RFC 1191. The default is 1.

TcpWindowSize = "faf0" hex (or 64240 decimal)
Specifies the receive window size advertised by the TCP/IP stack.

Exit your registry and restart Windows for the change to take effect.

Registry Editor Example
|NameTypeData|
|(Default)REG_SZ(value not set)|
|DefaultTTLREG_DWORD0x00000080 (128)|
|EnablePMTUBHDetectREG_DWORD0x00000000 (0)|
|EnablePMTUDiscoveryREG_DWORD0x00000001 (1)|
|TcpWindowSizeREG_DWORD0x0000faf0 (64240)|
-
|HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters|
-

Settings:
System Key: [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters]
Type: REG_DWORD (DWORD Value)

Disclaimer: Modifying the registry can cause serious problems that may require you to reinstall your operating system. We cannot guarantee that problems resulting from modifications to the registry can be solved. Use the information provided at your own risk.

Last Modified: October 18, 2000

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