1001 Secrets for Windows NT Registry
(Publisher: 29th Street Press)
Author(s): Tim Daniels
ISBN: 1882419685
Publication Date: 12/01/97

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I-316 If you use a RAS connection to route IP packets and are suffering from poor network performance, these registry entries can help you squeeze a little more performance out of your connection.

Hive: HKEY_LOCAL_MACHINE
Key: System\CurrentControlSet\Services\<adapter name>\ Parameters\Tcpip
Value Name: MaxForwardPending
Data Type: REG_DWORD
Value: 20

The MaxForwardPending value governs how many packets Windows NT forwards to a particular network interface at a given time. If you have a slow connection, changing this value really helps performance. The default value is 20. Restart the machine for any changes to take effect.

I-317 If your Windows NT machine seems to be suffering from lost IP packet syndrome, these registry entries can help you tweak your system for maximum throughput.

Hive: HKEY_LOCAL_MACHINE
Key: System\CurrentControlSet\Services\Tcpip\Parameters
Value Name: ForwardBufferMemory
Data Type: REG_DWORD
Value: 7420

The ForwardBufferMemory value controls how much memory Windows NT sets aside to store packet data in the packet data queue. Each packet buffer is 256 bytes, so the ForwardBufferMemory value should be a multiple of 256. When the packet data queue is full, Windows NT randomly discards packets.

I-318 Hive: HKEY_LOCAL_MACHINE
Key: System\CurrentControlSet\Services\<adapter name>\ Parameters\Tcpip
Value Name: MaxForwardBufferMemory
Data Type: REG_DWORD
Value: 0xFFFFFFFF

The MaxForwardBufferMemory value governs the total amount of memory Windows NT sets aside to store packet data in the router packet queue. This value must be greater than or equal to the ForwardBufferMemory value. If you don’t have IP routing enabled, this registry value is ignored.

I-319 Hive: HKEY_LOCAL_MACHINE
Key: System\CurrentControlSet\Services\<adapter name>\ Parameters\Tcpip
Value Name: NumForwardPackets
Data Type: REG_DWORD
Value: 50

This value governs the number of IP packet headers that can be stored in the router packet queue. This value should be at least as large as the ForwardBufferMemory divided by 256.

I-320 Hive: HKEY_LOCAL_MACHINE
Key: System\CurrentControlSet\Services\<adapter name>\ Parameters\Tcpip
Value Name: MaxNumForwardPackets
Data Type: REG_DWORD
Value: 0xFFFFFFFF

This value sets the total number of IP packet headers that can be stored in the router packet queue at a given time. This value needs to be at least as big as NumForwardPackets, if not larger. Restart your machine for any changes to take effect.

I-321 If you need to control the level at which your Windows NT machine supports the Internet Group Management Protocol (IGMP), then this registry entry is for you.

Hive: HKEY_LOCAL_MACHINE
Key: System\CurrentControlSet\Services\Tcpip\Parameters
Value Name: IGMPLevel
Data Type: REG_DWORD
Value: 2

A value of 0 prohibits all multicast support. A value of 1 lets the system send IP multicast packets. The default value of 2 lets the Windows NT machine send and fully participate in receiving IP multicast packets. Restart your machine for any changes to take effect.

I-322 If your aborted sessions aren’t properly cleaned up or if your idle but live sessions are dropped inadvertently, you may need to adjust these two registry parameters.

Hive: HKEY_LOCAL_MACHINE
Key: System\CurrentControlSet\Services\Tcpip\Parameters
Value Name: KeepAliveTime
Data Type: REG_DWORD
Value: 7,200,000

I-323 Hive: HKEY_LOCAL_MACHINE
Key: System\CurrentControlSet\Services\Tcpip\Parameters
Value Name: KeepAliveInterval
Data Type: REG_DWORD
Value: 1000

Both values are in milliseconds. The default value for KeepAliveTime is 7,200,000, or 2 hours, and the default for KeepAliveInterval is 1000, or 1 second. KeepAliveTime governs how often Windows NT sends a keep alive packet. A specific application can request that keep-alive packets be sent. If the target system is able, it responds with an acknowledgment. The KeepAliveInterval works with the KeepAliveTime and governs how often keep-alive packets are sent until an acknowledgment is received. If the target machine doesn’t respond and the number of retries exceeds the value of TCPMaxDataRetransmissions, the connection is terminated. Restart your machine for any changes to take effect.


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