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27. No "Forward Buffer Memory Tweak" in the TCP Optimizer ?

You may find the following "Forward Buffer Memory Tweak" recommended for tweaking TCP/IP on some tweaking sites:

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters]

"ForwardBufferMemory"=dword:00024a00
"NumForwardPackets"=dword:0000024a
"MaxForwardBufferMemory"=dword:00024a00
"MaxNumForwardPackets"=dword:0000024a


Note that tweaking Forward Buffer Memory is only necessary when Windows is configured as a router, i.e. to forward IP packets it receives, using multiple network adapters. By default Windows XP/2k/2k3 Server are all configured not to act as a router.

For all the above values to be considered at all, routing must be enabled in:
HKLM\SYSTEM\CurrentControlSet\Services\Parameters\IPEnableRouter=1 (default is IPEnableRouter=0).

In other words, tweaking Forward Buffer Memory is not necessary, and the above Registry values are ignored unless your PC is configured to act as a router (IPEnableRouter=1).

Furthermore, some of the numbers as recommended by other sites are not necessarily optimal. If you plan on using Windows as a router, here is our take on the optimal values:
- ForwardBufferMemory value should be set to a higher number than the default 50 x MTU rounded up to multiples of 256 (for example 100 x MTU rounded up to multiples of 256).
- NumForwardPackets, however, should be set to about twice the ForwardBufferMemory multiplier (set to 200 in this example), this is sufficient even if all packets are half the MTU size.
- the default MaxForwardBufferMemory value is 2MB, and is much better suited not to discard packets than the proposed by some sites "tweaked" value that equals ForwardBufferMemory. We recommend using the Windows default value, rather than limiting this maximum. Memory is only allocated up to this maximum buffer if the ForwardBufferMemory proves insufficient, so you're not wasting memory by leaving this at the default 2MB.
-MaxNumForwardPackets should be set to ForwardBufferMemory/256 (since that is the maximum number of packets, as limited by the ForwardBufferMemory).

Then again, tweaking Forward Buffer Memory is not necessary, and the above Registry values are ignored unless your PC is configured to act as a router (IPEnableRouter=1), forwarding packets over multiple network adapters. That is why the TCP Optimizer does not include the "Forward Buffer Memory Tweak".


  User Reviews/Comments:
    rate:
   avg:
by csryback - 2006-07-06 20:27
I get outstanding results in a LAN (2000 users) just modifying the parameter
NumForwardPackets to 200 or 250

to this work you have adjust too
IpEnableRouter=1
ForwardBroadcasts=1

Quintana Daniel
Electronic Technician & Network Administrator
by steelwolf - 2009-04-26 03:33
I am a bit unclear about the settings for this parameter. My network is just one laptop with a Belkin G+ MIMO router. If I am correct, I do not need to tweak this parameter? I either use my lan connection or wireless card, disabling the one not in use. my processor and memory usage setting are set to "programs", not as a ,"System cache", or,"background services".
Info: XP Pro SP3, 1.6Ghz pentium M, 2 GB's Ram.

I would appreciate any feedback,

Thanks,

SteelWolf
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