Optimize Broadband Cable Modem and DSL Connections

These settings allow you to boost the speed of your broadband Internet connection when using a Cable Modem or DSL Router with Windows 2000 and Windows XP.

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.

GlobalMaxTcpWindowSize = "7FFF" hex (or 32767 decimal)
Specifies the system maximum receive window size advertised by the TCP/IP stack.

TcpMaxDupAcks = "2"
Determines the number of duplicate ACKs that must be received for the same sequence number of sent data before "fast retransmit" is triggered.

SackOpts = "1"
Enables support for selective acknowledgements as documented by Request for Comment (RFC) 2018. Default is 0.

Tcp1323Opts = "1"
Controls RFC 1323 time stamps and window scaling options. Possible values are: "0" = disable RFC 1323 options, "1" = window scale enabled only, "2" = time stamps enabled only and "3" = both options enabled.

TcpWindowSize = "7FFF" hex (or 32767 decimal)
Specifies the receive window size advertised by the TCP/IP stack. If you have a latent network you can try increasing the value to 93440, 186880, or 372300.

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

Note: These optimized settings may not work with all ISP configurations, in which case the parameters should be returned to the default values.

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.

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