Default TTL

Default TTL determines the time in seconds and the number of hops a packet lives. While it does not directly affect speed, a larger value increases the amount of time it takes for a packet to be considered lost, discarded and retransmitted. A value that’s too small can cause packets to be unable to reach distant servers at all.

HKLM\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters

DefaultTTL=”64″ (DWORD, recommended setting is 64. Other settings that are widely used are 128 and 32)

Enable PMTU Discovery

When set to 1 (True), TCP attempts to discover MTU automatically over the path to a remote host. Setting this parameter to 0 causes MTU to default to 576 which reduces overall performance over high speed connections.

HKLM\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters

EnablePMTUDiscovery=”1″ (DWORD – boolean, valid settings are 0–>False and 1–>True. Many connections perform better with this entry at 1, however, if you prefer to set your upstream to send fixed 1500 packets, you might want to use 0 instead). When set at 1, establishing connections and initial transfer speed might slow down a bit, however you will get better throughput if somewhere in the path large packets need to be fragmented.

Enable PMTU BHDetect

Setting this parameter to 1 (True) enables “black hole” routers to be detected, however it also increases the maximum number of re-transmissions for a given segment. In most cases you’d want to keep BHDetect to 0 (False).

HKLM\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters

EnablePMTUBHDetect=”0″ (DWORD – boolean, valid settings are 0–>False and 1–>True. Recommended setting is 0)

Sack Options

This parameter controls whether or not SACK (Selective Acknowledgement) support is enabled, as specified in RFC 2018. SACK is especially important for connections using large TCP Window sizes.

HKLM\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters

SackOpts=”1″ (DWORD – boolean, recommended setting is 1. Possible settings are 0 – No Sack options or 1 – Sack Option enabled).

TCP Max Dup ACKs

This parameter determines the number of duplicate ACKs that must be received for the same sequence number of sent data before “fast retransmit” is triggered to resend the segment that has been dropped in transit.

HKLM\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters

TcpMaxDupAcks=”2″ (DWORD – range 1-3, recommended setting is 2).

Patches

S. Guide Tweak Patch

Generic patch for Windows XP and Windows 2000 (all versions). This patch will optimize your TCP/IP Registry settings for high speed Internet connections. To install, extract the .inf file first, then double-click (or right-click on filename and choose install from the pull-down menu) and reboot for changes to take effect.

You can download it here

http://www.speedguide.net/files/sguide_tweak_2k.zip

S. Guide Patch PPPoE

Generic patch for Windows XP/2000 and DSL connections using PPPoE. This patch will optimize your TCP/IP Registry settings for high speed Internet connections. It is specifically designed for PPPoE DSL connections. To install, extract the .inf file first, then double-click (or right-click on filename and choose install from the pull-down menu) and reboot for changes to take effect.

You can download it here

http://www.speedguide.net/files/sguide_tweak_2k_pppoe.zip

WinXP DNS Cache Patch

Patch Windows 2k/XP not to cache failed DNS entries. By default, when a DNS lookup fails (due to temporary DNS problems), Windows still caches the unsuccessful DNS query, and in turn fails to connect to a host regardless of the fact that the DNS server might be able to handle your lookup seconds later. This patch fixes the problem by configuring the DNS client to continue sending queries to an unresponsive network. To install, save to your HD, unzip the .reg file, then double-click the filename.