Dear Satellite friends,
http://www.psc.edu/networking/perf_tune.html did not help to improve the performance of an Windows NT environment as some other buffers were limiting.
We noticed that changing some other registry entries were also needed for having a good performance (some 160kBytes/s file transfer) on a 400ms RTT network.
Thanks to all the people who responded and helped me to find the right doc's at Microsoft.
I know that the numbers we used for the registry entries are not the optimum, we are still working on that :-)
Please refer to the next page for Windows NT:
http://premium.microsoft.com/msdn/library/winresource/dnwinnt/f1d/d1e/s8516.htm
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
ForwardBufferMemory REG_DWORD Number of bytes
This parameter determines how much memory IP allocates to store packet data in the router packet queue. When this buffer space is filled, the router begins discarding packets at random from its queue. Packet queue data buffers are 256 bytes in length, so the value of this parameter should be a multiple of 256. Multiple buffers are chained together for larger packets. The IP header for a packet is stored separately. This parameter is ignored and no buffers are allocated if the IP router is not enabled.
Default: 74240 (enough for fifty 1480-byte packets, rounded to a multiple of 256). Set at 742400.
NumForwardPackets REG_DWORD Less than 0xffffffff
This parameter determines the number of IP packet headers which are allocated for the router packet queue. When all headers are in use, the router will begin to discard packets at random from the queue. This value should be at least as large as the ForwardBufferMemory value divided by the maximum IP data size of the networks connected to the router. It should be no larger than the ForwardBufferMemory value divided by 256, since at least 256 bytes of forward buffer memory are used for each packet. The optimal number of forward packets for a given ForwardBufferMemory size depends on the type of traffic carried on the network and will be somewhere in between these two values. This parameter is ignored and no headers are allocated if the router is not enabled.
Default: 50. Set at 500.
TcpSendDownMax REG_DWORD Number
Specifies the maximum number of bytes queued by TCP/IP.
Default: 16384. Set at FFFF (hex).
TcpWindowSize REG_DWORD Number
This parameter determines the maximum TCP receive window size offered by the system. The receive window specifies the number of bytes a sender may transmit without receiving an acknowledgment. In general, larger receive windows will improve performance over high delay or high bandwidth networks. For maximum efficiency, the receive window should be an even multiple of the MTU of the underlying network less the size of the standard TCP and IP headers (40 bytes).
Default: The smaller of: 0xffff OR the larger of: four times the maximum TCP data size on the network OR 8192 rounded up to an even multiple of the network TCP data size. Set at 58400.
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet \Services\Afd\Parameters
DefaultReceiveWindow REG_DWORD Bytes
The number of receive bytes AFD will buffer on a connection before imposing flow control. for some applications. A larger value here will give slightly better performance at the expense of increased resource utilization. Note that applications can modify this value on a per-socket basis with the SO_RCVBUF socket option.
Default: 8192. Set at ffff (hex).
DefaultSendWindow REG_DWORD Bytes
Same as DefaultReceiveWindow, but for the send side of connections.
Default: 8192. Set at ffff(hex)
Kind Regards,
Jack Stiekema
Philips Digital Video Systems, DTS
Phone +31 6 22240066
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